How do I export animation data stored in actions using the Python API?

You can set an object's action like:

object.animation_data.action = action

But note that you should check first, that animation_data is not None (which is the case for objects with zero keyframes set).

frame_set() is not a bad choice. You could also evaluate the F-Curves one by one and avoid the frame changes, but it's easier to set the frame and get the transformations ready to use (e.g. as 4x4 Matrix). It's also ensured that all modifiers, drivers and such are applied.

Quick F-Curve example:

bpy.context.object.animation_data.action.fcurves[0].evaluate(5)
#~ -3.2612

bpy.context.object.animation_data.action.fcurves[0].keyframe_points[0].co
#~ Vector((1.0, -3.2612))

bpy.context.object.animation_data.action.fcurves[0].keyframe_points[0].interpolation
#~ 'BEZIER'


For this kind of shape (the zero) using convex hull seems to work better than using mesh.
From the manual page on collisions:

Convex Hull
A mesh-like surface encompassing (e.g. shrink-wrapped over) all
vertices (best results with fewer vertices). A convex approximation of
the object, which has good performance and stability.

Mesh
Mesh consisting of triangles only, allowing for more detailed interactions than convex hulls. Allows simulating concave objects, but
is rather slow and unstable.

In your case, using convex hull stabilizes things much more.

Here is the difference between mesh and convex hull in your case:
Mesh:

Convex Hull:


I think the quickest way to deal with this issue would be to load the reference image behind the mesh, tab into Edit mode with Proportional editing on and quickly move the tube into place in sections. With proportional editing on you won't have to move every vertices. If you find the proportional editing is distorting your tube shape just decrease the strength/area of the tool's effect.

Also, I don't think you're going to be able to have a perfectly curved innner edge on the curve and have it snapped exactly to the sphere's surface because of the hard angles of the sphere (see screen shot). This is because you still want the curve to be smooth which will require some subsurf to be applied.


How to create UVs for a number of duplicated objects

You could pick one object as a template and setup the material and texture.

After that select all objects which should get the material settings assigned and add the template as last object to you selected object (must be the active object).

Ctrl-L Opens the Make Links Popup

Select Materials, after that open the Popup again and select Transfer UV-Maps.

Video Tutorial on Make Links
Documentation


How would I recreate this warped grid-like pattern?

I've tried both Surface Defom and Lattice (as recommended by Susu). It looks like lattice is more convenient in your case as the cage can be simpler:

Create your tile, subidive it a bit, give it a Subdivision Surface modifier, array it, give it a Lattice modifier.

Create a lattice, scale it in Object mode so that it contains the tiles, give it a bit of Resolution in the Object Data panel, but you can keep it flat on the W axis with a value of 1. Create 2 shapekeys in the same panel:

Keep the second shapekey selected, go in Edit mode, enable the Proportional Editing option, move the vertices to deform the lattice, the object will deform as well. Once back in Object mode, play with the shapekey Value:


Is it possible to reproduce Maya/ Houdini target/ point weld operators inside of Blender?

3DSMax also has an equivalent Target Weld, but as far as I know Merge at Last is Blenders closest operator. Unfortunately workflow involves dealing with the menu as you mention, making it unsuited for repeated use.
One possible workaround is using Blender's Auto Merge feature. While in Mesh Edit Mode, from the 3D View Header > Options menu activate Auto Merge.
Just combine it with regular Move operator or the Tweak tool, overlapping vertex should automatically be removed.

Having vertex snapping turned on from the magnet icon on top makes it more reliable.
You can also toggle it on or off from the Tools Options from the 3D View Sidebar or Properties Window.


Select the material, press Shift+L and choose material.

This will select all the objects sharing that material.

If there are no selections either you have 2 material slots with the same material on your object or the object in question is in another scene.


How do I make a pop up dialog that goes away when pressed "ok"?

When you press "Ok" you are calling the execute method of the operator, in which you are re-calling your operator. Get rid of bpy.ops.wm.myop('INVOKE_DEFAULT') in the execute method.

Blender 2.8 uses annotations for properties.

Blender 2.8 uses strict naming conventions for operator and panel class names. For the operator with id wm.myop the class needs to be named WM_OT_myop.  Please check the system console for errors.

Test script.  Added to text menu of text menu for example sake./

import bpy

class WM_OT_myop(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "wm.myop"
    bl_label = "Simple Object Operator"
    # annotations in 2.8
    name : bpy.props.StringProperty(name="Name", default="")

    @classmethod
    def poll(cls, context):
        return context.active_object is not None

    def execute(self, context):
        return {'FINISHED'}

    def invoke(self, context, event):
        wm = context.window_manager
        return wm.invoke_props_dialog(self)

def menu_draw(self, context):
    self.layout.operator("wm.myop")

def register():
    bpy.utils.register_class(WM_OT_myop)
    bpy.types.TEXT_MT_text.append(menu_draw)

def unregister():
    bpy.utils.unregister_class(WM_OT_myop)

if __name__ == "__main__":
    register()

    # test call
    bpy.ops.wm.myop('INVOKE_DEFAULT')

In order to make the operator work as part of a 'floating menu' you have to set the operator_context property of the layout beforehand, which basically allows to display the popup:

import bpy

class WM_OT_myop(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "wm.myop"
    bl_label = "Simple Object Operator"

    name: bpy.props.StringProperty(name="Name", default="")

    @classmethod
    def poll(cls, context):
        return context.active_object is not None

    def execute(self, context):
        return {'FINISHED'}

    def invoke(self, context, event):
        wm = context.window_manager
        return wm.invoke_props_dialog(self)

class Custom_MT_Menu(bpy.types.Menu):
    bl_label = "Custom Menu"
    bl_idname = "OBJECT_MT_custom_menu"

    def draw(self, context):
        layout = self.layout
        layout.operator("wm.save_as_mainfile").copy = True

        layout.operator_context = 'INVOKE_DEFAULT'
        layout.operator("wm.myop")

def register():
    bpy.utils.register_class(Custom_MT_Menu)
    bpy.utils.register_class(WM_OT_myop)

def unregister():
    bpy.utils.unregister_class(Custom_MT_Menu)
    bpy.utils.unregister_class(WM_OT_myop)

if __name__ == "__main__":
    register()

    # The menu can also be called from scripts
    bpy.ops.wm.call_menu(name=Custom_MT_Menu.bl_idname)

Further reading: How to call a confirmation dialog box?


add an object from bpy.data.objects in context scene?

Link to collection

bpy.context.collection.objects.link(stuck)

or for < 2.8 link to scene

bpy.context.scene.objects.link(stuck)


how to adjust a render to match the 3d view?

To reduce the amount of noise in an image rendered by Cycles, you can do the following:

Turn up your samples

Under the Sampling section of the Render tab, you can adjust the number of render samples.
Increasing the samples will increase your render time proportionally, but you will get cleaner images.

Turn on denoising

As @kim-holder mentioned, you can turn on denoising to reduce the noise in the image. This is a new feature added to Cycles in 2.79
This will usually do a good job of getting rid of noise, but often softens the image and blurs edges to a certain extent.

Dim the lights

It may also be that your lights are set to be too intense. Lowering their intensity should help to reduce fireflies (the bright white spots on your image)

Turn on "Filter Glossy"

Filter Glossy reduces fireflies on glossy surfaces by blurring them slightly. See here for more information.


How would I create this moving flowy mesh on a transparant mesh?

Extreme deformation meshes with blender tends to break the geometry of the mesh. Here I take a simple cube with 2 faces deleted and some twist modifiers. You animate by increasing the twist values.

Otherwise you could use a procedural texture on a sphere, you map it to an empty that has an animated position. Use alpha values to cut holes in the sphere mesh. Remember to make the inside traceable in Blender Internal, otherwise Cycles will do this automatically, allowing you to cast shadows inside.

And here is the example blend file I made these images with:


When your in edit mode, press ALT H. This unhides objects. What happened in your case, was that you accidentally pressed H (hide) while you where in edit mode with everything selected.


It sounds like the some vertex groups have been connected to the wrong bone in the armature.  Click on the bone that is causing problems then go into weight paint mode and look at what parts of the mesh are being influenced by that bone.


The code probably is working as expected, but it’s doing something else you didn’t know it was doing: when blender runs Python code, the UI stops. This usually isn’t a problem since most code finishes within a few seconds, but in the case of this code, render times are being waited on. So until all the scenes finish rendering, the UI would be frozen. I agree with the commentor that suggested you run the code in a minimal blend file with just simple cubes and short frame ranges in each scene to test this diagnosis.


Get the rotation of an object in the game engine

The method for accessing an object's rotation varies depending upon which rendering engine you are using.

In either Blender-Internal or Cycles, you can access an object's rotation by using the Python reference bpy.context.object.rotation_euler or just object.rotation_euler. In your script, just call that reference and set your other object's velocity based on that.

In the Blender Game Engine, you need to instead use object.worldOrientation.to_euler() to retrieve the object's rotation. For example:

from bge import logic
cont = logic.getCurrentController()
obj = cont.owner
rotation = obj.worldOrientation.to_euler()
print (rotation.z)


Adjust the image offset and image crop for multiple strips

I found a solution, there is a script called Extra Sequencer Actions

http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Sequencer/Extra_Sequencer_Actions

http://blenderartists.org/forum/showthread.php?248129-Extra-Sequencer-Actions

Initially I came across it they were mainly talking about batch editing proxies. But after installation I found it had and many sub menus under the Strip menu.

It behaves as desired.


I Extruded up with z and scaled down 8 times but have a square to deal with

If you want the center to be just vertices (As shown in @Neil's answer), click alt+m while only selecting the square in the center.
But if you want the center to be a circle:

Select only the center square
Press Space bar (EDIT: Press F3 instead as Space bar was for an outdated version of Blender)
Type in sphere and click the to sphere option.
mess with the values in the tool bar (Scroll to bottom of toolbar) to get your desired result.


Render parts of object(s) only when they are within a defined area

With Holdout:

Create a layer with the train and with a holdout object both visible (make sure that the holdout object is alpha blend and no shadow):

Create a second layer with neither of these 2 objects visible:

Render and mix in the Compositor through a Color > Alpha Over:

Or create a black and white image that will allow you to mask the left part:

Create 2 layers, one with the train, one without, use the black and white image as a mask in the Compositor:


The following is "fixing" only, as there are few bad things in your model.
For the handle, you have inner faces, that should be deleted (only did 2 in the gif below):

Also have inverted faces. You can see that activating face orientation, then use ShiftN to solve it (except for the last issue, see below):

The handle also has inner part that should not exist: remove them.
Last step, the face that is bad. It is a ngon. Probably you did after removing some parts.
So delete the bad parts and use existing one to replace it.
Can do it by selecting a good slide, duplicate and rotate it ShiftDR and adjust as closely as possible to the bad part.
To do it, make sure the 3D cursor is placed at the center and it is the origin point for the rotation, also, use snap with increments (see what is surrounded by green below):

Once all slices are recreated, select all A and merge duplicates M then "by distance" (tune the distance in the operator panel to be sure to remove the wanted doubles).
Again, this is fixing only, and you'd better redo it all as exercise.
All these done, you should have a cup with no more cracks:


Copying Y scale value onto multiple objects

Here is a script (I don't know if there is another option) for now

copy and paste the script in the blender text editor
select the objects
the object with the right scale should the active object (yellow outline , others red )
in the text editor click Run Script

import bpy

s= bpy.context.object.scale[1]
for obj in bpy.context.selected_objects :
    obj.scale[1] = s


How do I render only the particular view layer I want instead of always including a full composite pass?

Okay, I figured out the answer:
Under RENDER and VIEW LAYER, make sure that Use for Render is UNCHECKED. This will eliminate that particular layer. In the compositor, plug in the the layers that you want to export per my initial graphic. Or, select the checkbox for Render Single Layer (while making sure you are actually on that layer).


I was unable do this using the technique above, because I could not figure out how to prevent re-setting of the location.  Therefore, I used the following technique:  create a single object, copy it with ob.copy, put copies into scene object list, and then update the scene.

bpy.ops.mesh.primitive_cylinder_add(vertices=numVertices, radius=columnSize,
    depth=height,location=loc)
ob = bpy.context.object
obs = []
sce = bpy.context.scene

f = open('input.data', 'r')
for line in f:
    values = line.split()

    x = float(values[1]) / scaleXY
    y = float(values[2]) / scaleXY
    height = float(values[3]) / scaleHeight

    copy = ob.copy()
    copy.location += Vector((x,y, 0))
    # copy.data = copy.data.copy()
    copy.scale.x = copy.scale.x * height / 2
    copy.scale.y = copy.scale.y * height / 2
    copy.scale.z = copy.scale.z * height
    obs.append(copy)

for ob in obs:
    sce.objects.link(ob)

sce.update()


How to not select objects behind main camera with script in Python?

Add a plane on perspective camera looking forward.

As a quick work around is to add a plane looking forward on a perspective camera, by adding this else clause circa line 32 of original code.

if not is_persp:
    # add a 5th plane to ignore objects behind the view
    n = normal(frame[0], frame[1], frame[2])
    d = -n.dot(origin)
    planes.append((n, d))
else:
    n = (matrix * Vector((0, 0, -1)) - origin).normalized()
    d = 0
    planes.append((n, d))

A cameras line of view is its negative local Z axis. All above does is adds a plane that has a global normal looking in the same direction.

Image shows plane with normal, the Z axis pointing in direction of camera's -Z axis.


How to render multiple scenes in succession from the timeline?

For rendering more Scenes created in one blend file use Video Sequencer (called VSE).
Scene_Cube

Scene_Sphere

Create a third New scene, switch to Video Editing layout and  with mouse hovering above Video Sequencer editor Add Shift+A Scene strips and organised on Timeline as needed.

From Video Sequencer properties panel N (with Scene strip selected in timeline) under Strip > Scene > Camera you can choose what camera object should be used (if you have more than one in that scene).
Or you can also use one camera in Scene_Cube linked to Scene_Sphere.


How to use a standalone blender (not using global preferences)

The global settings are stored in :
%APPDATA%\Roaming\Blender Foundation\Blender for windows
~/.config/blender for linux
where there are folders for each version (2.72, 2.73, ...)
These setting can be ignored if you create a config (startup file, user preference file, bookmarks, recent files), a scripts (addons, presets) or a cache (BVHs, temporary) (or both) folder in the version folder of your installed or unzipped Blender : C:\blender\blender-2.74-rc1-windows64\2.74 \config
If the folder(s) exists and is empty, Blender will use the default settings. Global settings can be copied there and then modified without changing global settings.

Thanks to jesterKing and iKlsR


Okay so I figured it out and will post the answer just in case a new 2D animator runs into the same issue.

The problem I had is solved with setting keyframes for the new layers (ink, color, shadows, highlights, etc..) on another frame in the dopesheet.
Because I had those layers only active on 1 frame in the dopesheet the image showed through the whole animation.


You can achieve this effect by creating and texturing your wall before splitting it up into different pieces.

After you created your wall you can use the cell fracture add-on to break your wall down. For smashing your wall with a wreckingball this would create the desired effect.

For an in-depth tutorial of this method see the youtube vid made by CG Geek:
https://www.youtube.com/watch?v=XUUi2AdLtmk

Good luck.


Placing cubes in a grid is very slow (using python script)

As far as I can see the code creates for each data point a seperate Blender Mesh Object. For large datasets this will make everything super slow.
I would recommend you to create only one mesh per label-class so that with 3 label classes you would have only 3 Mesh Objects.

Since you are actually using my code, I took your question as feedback and updated it accordingly on github.
https://github.com/cagcoach/BlenderPlot


I am having very slow performance running Blender

Make sure you have your video drivers up to date since Blender's UI is run entirely through OpenGL. Just search for your graphics card (GPU) online. If you do not know what model of GPU you have, then try going to the GPU brand's website usually you can find which brand of GPU you have somewhere on your computer's case or the box it came in. The brand will usually have an easy way to find out what GPU you have and provide you with updates.


Create a bezier curve in the shape of your rope.
Create a rope segment with some seamless texture.

Make sure that the bezier curve and the rope segment have origin in the same location.
For the rope segment add Array modifier, set length to Fit curve,
select your bezier curve and tick Merge so it won't generate vertices doubles.
Add Curve modifier and select your rope segment.
Now you should have something like this:

Close the ends of the rope model.


Why does Blender show trees in my glass cube?

The screen space reflections in Eevee especially with highly reflective materials, for example metal with 0 roughness or glass like yours, will always show the environment like a mirror.
In Material Preview (Eevee is used, even if Cycles is set as render engine), you have a few HDRIs to choose from and if no Background is set up manually, Blender will use it's preinstalled HDRIs.

The default one used is the 3rd one.
Those are only for convenience and not necessarily used for final results.
Also the place where you set your own world environment, be it a color or HDRI, is in the World Properties:

The easiest way to set up your own HDRI, is to go in the Shading tab and do the following:

Switch the mode to World

In the Shader Editor press Shift+A to add a new Environment Texture Node.

Connect the Color output of the new Node to the Color input of the Background Node.
Now you can load a HDRI in the new node. You can find free HDRIs online (HDRIHaven for example). Beware though, they are rather big files if you want good resolution.
Lastly if you have an HDRI loaded in, you want to turn the Scene World option in the Preview Mode on, so it will use your HDRI and not the default one anymore.

Here how it can look:

mind that i did not set the cube to glass
In case you just want a color, skip all the steps and directly in the World Properties the color field above the Strength can be used to change and adjust the color used for your scene. I'd advice though against using the pure color, as it really is nothing else then making the entire scene be in that one color.
Here how that can look:

There are a lot tutorials out there, worth watching, as there are so many features, that it can be overwhelming at the start.
Happy Blending


Snap all vertices to grid when translating (not center of selection)

You can move the Origin of the object, which is currently your "center of object", to the grid.
In Edit Mode, select a vertex on the grid, then press Shift S and Snap to Selected.
Then in Object Mode, go to the Tools Tab of the Tools Editor, Set Origin, and Origin to Cursor.
I'm in 2.79 - hope you can find the commands in 2.8.


Blender Can't detect 3D hardware accelerated Driver

You should get "software" OpenGL:

Go to this link: http://download.blender.org/ftp/sergey/softwaregl/
Pick your OS version (86/64).
Put the opengl32.dll file into your top Blender installation folder (C:\Program Files\Blender Foundation\Blender). This should be the same location as your blender.exe file.

Blender should start.


Thanks to "stilltrying" from blenderartists.org, I found my answer.

The little Normalize All option called "Lock Active" is on pr default, meaning the active vertex group was unchanged. This of course leads to the relative weights being changed, thus causing the mesh to move due to the Normalize All operation.


How to pack all linked data inside the current .blend file

There is now an add-on (BlendFile Utils) that comes with Blender (2.77 and newer).

That supports packing a file and all its dependencies into an archive.

Note that this is a stand-alone tool which can be run from the command line, the same code used on the Blender-Cloud for downloading blend's as zipfiles and was used for exporting Blend files to the renderfarm for the short film Cosmos Laundromat.


In Blender 2.80, I've had some success with something simpler that previous @johnzero7's solution :

collection = bpy.data.collections.new('My Collection')
bpy.context.scene.collection.children.link(collection)

# NOTE the use of 'collection.name' to account for potential automatic renaming
layer_collection = bpy.context.view_layer.layer_collection.children[collection.name]
bpy.context.view_layer.active_layer_collection = layer_collection


Make an object stop interacting with fluid

I assume that you're using the original Elbeem fluid simulator.

With particle systems, you can isolate them by placing them on different layers.
However, with the Elbeem fluid simulator, it basically ignores the layers, and
treats everything as being on the same layer. So moving the obstacle to a different layer is not an option.

Unfortunately, (unless I'm overlooking something), the eye/camera icons that are next to the 'Fluid' button in the Physics tab > 'Enable Physics for' section appear to do nothing (at least for the Fluid Obstacle Object). The eye/camera icons in the Outliner only effect the visibility of the fluid object in the 3DView/Render respectively.
It would be great if they worked in a similar fashion to particles; then this would be very simple to do.

I tried scaling the obstacle glass/mug (to isolate it from the fluid),
and then moving it outside the domain.
However, in each case, the Elbeem fluid simulator seemed to work up until the
point where the obstacle was moved outside the domain. It didn't crash, it just seemed to stop working.

This is probably a bug, but since development on the original fluid simulator has ceased, and development effort is instead being directed to the MantaFlow simulator; you currently will have to work with what you have.
More information on the Blender implementation of Mantaflow at:
https://blenderartists.org/t/lets-talk-about-mantaflow/644346

and more information on the Mantaflow framework:

http://mantaflow.com/

Another option may be to look into the Flip Fluid Add-on by RLGuy
(I'm not that familiar with the add-on, but he did present some disappearing box type demo videos) It's a paid add-on, approx. $US 76. More details at:
https://blenderartists.org/t/flip-fluids-addon-a-liquid-fluid-simulation-tool-for-blender/702503

The method that seemed to work, was adding vertex keys to the obstacle (using a
Shell proxy object) and then moving the obstacle (while still keeping its
center point within the domain) such that only the obstacle's vertice were
outside of the domain. (This might also work with scaling and moving the obstacle, but I didn't try it).

When you add keyframes for vertex keys, you need to check the 'Export Animated Mesh'
option for the fluid and the Obstacle objects. (This isn't necessary for loc/rot/scale
keyframes).

Here's a blend file in case I forgot to mention some details:

Select the fluid domain from the Outliner,
Switch to the Physics tab in the Properties Area, and
Press Bake.


the mesh is still snapped even i turned off snapping

It looks like you have a shrink-wrap modifier on your mesh. It's not uncommon to use that when retopoing.


It is simple:

def unregister():
    bpy.app.handlers.scene_update_pre.remove(my_handler)

Blender will call unregister() in the moment you untick the addon in the User Preferences.

my_handler is a function in the global scope of your script, and you append it to the scene update handlers. You can remove it in the same way, by giving a function reference to remove(). It doesn't work if you try to remove a handler callback from outside, because another script hasn't the same function.


Mouse Click alone takes precedence over "Regular Key Pressed as Modifier"+ Mouse Click

DerekWatts over at BlenderArtists answered my question in this topic.

Apparently it's a known issue and it's fixable by changing the order in which they appear in the hotkey list. Disabling the original left-click-only hotkey and add a duplicate at the bottom of the list fixes it.


Place an object on each face of a polyhedron

Let's say you have an octahedron and a gear and you want to have a gear on each of the faces of the octahedron.

Select the gear, then shift select the octahedron (so that both are selected but the octahedron is the active object)

Then press CtrlP and select parent to vertex.

Set the duplication to faces.

The advantege of this is that both objects remain editable, and chhanges on the duplicated object will be applied to each one of the instances. Once you are happy with the results you can Make Duplicates Real by pressing Ctrl+Shift+A

EDIT:

Both objects must be at a common origin.


Why are the camera and lamp objects appearing in the OpenGL render?

OpenGL render renders what you see in the viewport to a texture:

In the viewport, go to the Properties panel (N) and check "Only Render" in "Display".

OpenGL render again, and:

So, yes, it's a feature.


Export UVs to .png - output with alpha is different when launched from command line

I did exactly the same thing you did, exported the UVs from the Suzanne.

Though i did export it twice with once default opacity 0.25 and once with it set to 1 as you use in the script.

The code is taken from the Scripting Tab bottom left window. Here we can see as in the picture below, the default 0.25 function framed red(default value is optional and does not show up in the function used), the value of 1 (is not default, so the value shows up as parameter) in green:

bpy.ops.uv.export_layout(filepath="..\\Suzanne.png", size=(1024, 1024))

When compared to the one you use, there is a significant difference. Opacity by default when using the menu is 0.25, while in your script you use "opacity=1".

Using:

bpy.ops.uv.export_layout(filepath="..\\Suzanne1.png", size=(1024, 1024), opacity=0.25)

i got the exact same image as i got from when i used the menu function without changing the opacity.

So i would suggest you try your script with the adjustment of the opacity to "0.25".
That should do the trick.


Is it possible to make floor constraint base on surface detection?

Try changing the origin of the cube to any vertex on the bottom of the cube:

Select the vertex in edit mode.

Press ⇧ Shift + S to get the cursor menu and then choose Cursor to Selected.

Then in object mode get the object menu and set the origin to the cursor.


I downloaded your file, and though the applied material seems to have a reddish color in the material slot, the base color is light grey which is also what is appearing in the viewport views. When I changed it, the color of the model changed as well. Since the UV unwrap looks fine, I went one further and used nodes to add a checker texture just to test and it works fine. See below:

As you can see, the texturing seems fine. Is there something else i'm missing that is not working for you?


One-material Gradient between two objects? (Object Node/Manifold complications)

I found out what I needed not even ten minutes later lol.
What I did was set the origin points in the same places of objects I wanted to have a shared gradient, and where exactly it was set would be the start of a gradient.
Then I used the "Object" output from the Texture Coordinate node instead of "generated" in my setup to actually refer to the aforementioned origin points.

You can't even tell the fur is a different object!


How to model an accurate parabolic mirror with a known focal point?

Add mesh z surface

Enable the add mesh extra objects addon, then from add menu choose add > mesh > math function > math z surface

The equation of a paraboloid with focus f is

(x ** 2 + y ** 2) / (4 * f)

paraboloid with focus at (0, 0, 1)

Thickness can be added with the solidify modifier.


How to make an object with particles on it looks partially wet

Although fluid simulation may be your best bet, here is a way to use dynamic paint to simulate an effect similar to your photo.

To create the dynamic paint effect, I made some blobby "fluid like" meshes to act as dynamic paint brushes.  The lupi mesh (and a coconut flake mesh, for the particle system) were the canvas.  From right to left: the meshes including the brush objects; the dynamic paint effect on the canvas; the result on the material.

The material on the Lupi is what uses the wetmap as a factor to mix between two principled shaders.  One shader, the "wet" shader, has a red tint (varied with a noise texture) and more glossiness via a clearcoat.

Getting the dynamic paint to apply to the coconut particles is more complicated.  After the particle system is set up on the Lupi mesh (I used a "hair" type of particle system), it is necessary to apply a Particle Instance modifier to the coconut shreds - otherwise each particle will not act as its own separate Dynamic Paint canvas.  As mentioned before, the coconut shred mesh has a Dynamic Paint canvas applied to it.

The coconut particle material is much simpler, it's just got a base color of white (for "dry") and a reddish tint plus a clearcoat (for "wet"), with the wetmap as the factor of a Mix shader.

The above is not a step-by-step but hopefully it provides guidance as to the general technique.


How to do this type of trailing effects?

In order to reproduce the effect it is useful to know how it would have originally been produced.
At the time of the original effect being produced (early 1970s) there were not the digital tools available now. All video effect would have had to have been produced either via completely manual processes or via analog video editing techniques. In this particular case the effect is produced via video feedback where the existing image is fed back into the next frame so as to produce the 'ghosting'.
The video would have been shot in reverse (so the ghost images would have projected back from the text instead of coming out of the background) and the frame sequence reversed (by playing back in reverse). Multiple instances of the same shot would have been overlayed (with colour adjustment) and used to mask out the preceeding sequence so as to layer multiple colours over each other to produce the final shot.
We can produce similar results with a very similar (but much less labour intensive) process.
The first step is to set up the 'video feedback' to produce the ghosting. This has already been covered in https://blender.stackexchange.com/a/212906/29586 where it's used to feed back the previous frame for a 'life' simulation. The same technique can be used for other feedback effects.
Setup the scene with the camera pointing at a plane. Place your 'text' object (or whatever you want to 'ghost') in view of the camera.

Set the output path in the render output properties to a suitable location and create the material for the plane.

The Image Texture is set as a 'sequence', pointing at the same location as the render output location. The number of frames should be set to at least the number of frames of your animation and the Offset set to '-1' to indicate it should be one frame behind the render.
Rendering the animation should result in no change in the image (since the rendered image from the previous frame is the same as this current frame).
Alter the material so as to inject a difference between the frames and show/hide your text at appropriate times. I opted for a rotation, zoom and distortion - similar if this had been achieved with a 'real' camera, producing the following material and result.

Now the VSE can be used to combine and layer mulitple sequences together with Modifiers used to adjust the colours. The final frame is retained at the end for persistence.

Note that here I've imported the Strip from the relevant frames of the redered result. In the strip properties (on the right) the 'Reverse Frames' allows you to reverse the sequence. I've added a 'Color' strip at the bottom for a black background and set each of the 'layers' Blend mode to 'Screen' so that they overlay. Duplicating the strip and offsetting each duplicate gives the different 'layers' and the Modifiers can be used to adjust the colour with a Color Balance modifier.
This produces the following result :


All credit for this answer goes to the discussion here.

The data is stored in the grease pencil annotations:

bpy.data.grease_pencils["Annotations"].layers['RulerData3D']

Specifically, to get a list of all length measurements currently in the scene:

lengths = list((s.points[0].co - s.points[-1].co).length for s in bpy.data.grease_pencils["Annotations"].layers['RulerData3D'].frames[0].strokes)


Mouse wheel rotates instead of zooming in

That generally happens if you press Ctrl + Alt + Scroll Wheel or Shift + Alt + Scroll Wheel by default.

The fact that it is doing it by default may mean that you either changed the keyboard shortcuts in Blender preferences or you have a stuck key in your keyboard.

As far as I know there is no keyboard shortcut to permanently set this behavior by default


Why is the camera in the viewport smaller than the focal length suggests it should be?

The size of the camera in the viewport is not the same as the focal length. Scaling the camera object won't change the focal length or the rendered image, but will change the size in viewport.

For focal length = 32mm, the camera object will look like the principal plane is 1 BlenderUnit away from the camera center. This is probably an intuitive scale so that the camera object does have a fitting size for a usual scene. If it were acutally 35 BlenderUnits big, everyone would scale it down right away.


Blender 2.8 EEVEE render out viewport like old openGL render


How to make a large mesh smaller and workable?

Some ways to reduce interaction time. Consider Please

Work in wireframe mode when that is possible.  You need not work in render mode all the time.
Change maximum draw type for some objects to wireframe
Turn off Eye display of less important items for preview in outliner.  Camera Render Stays On.  Sometimes Groups can help this.
Bill board texture technique game style. A complex fence might be rendered once and then the texture put on blender planes. Crude and quick display substitute. Eye Display Only. Camera Render off.  Same location as the complex fence.
Working in local mode sometimes to isolate editing ... key / to enter and the same key to exit

Once a array modifier with repeat N on a meshA is applied and become meshFinal ...

the number of vertices of MeshFinal = N * (number of vertices of MeshA)

Once can reduce such vertices sometimes by using a Particle System with can produces meshes with a shared vertex datablock.   Configuration Settings .. Editing ... Duplicate Data ... Mesh may affect this.  The object size overhead is present in this case.


Speed control not slowing my video in the video editor

To learn about the various Speed Strip options, read/watch this post:
https://blender.stackexchange.com/a/185894/37272


Baking from high poly gives unexpected results

On high poly object go through any modifier that may affect the baking and turn them off for render like this:

In addition, make sure you follow this steps too posted here:
High Poly to Low poly normal bake looks weird


Your current bake setup is set to Normal baking. I believe what you're attempting to do (if you're following that tutorial) is either Combined or Diffuse (colour) baking.


How to set up SSS on cycles for efficient rendering

TIP: You can adjust subsurfacing Strength to render faster.
Lower subsurface values === Faster Rendering.
This is most easily possible with the Principled BSDF shader introduced in Blender 2.79, which allows the use of subsurfacing in the same shader as the main material.
This is an example skin shader rendered with Principled BSDF with 100% subsurfacing:

Here are a few more images adjusting the SSS value respectively:

As you can see, adjusting the values off SSS amount produce a slightly lower SSS result, but give you around 10 seconds lead on each frame's render time.
This is obvious information, however, and you probably know this already.
Since you are using SSS to fake the look of orange juice, I decided to try and set up a material for it that would look about the same, but render faster without/with little SSS.
First I checked out this reference image:

I decided to make a node setup that would allow the material to be changed in between multiple different materials that would "fake" the look of orange juice, and change render times. It allows for more SSS for more realism, while sacrificing time, and diffuse+glossy+transparent for less render time.
Here is the node setup:
With SSS, this is about the type of material color we are going for:
Here is the improved SSS render:

This is a general SSS render:
This is a volume absorption + glass shader render:
This is a volume absorption + transparent render:
As you can see, the material color changes drastically, but they all stay around the same general look. The render times change quite a bit too. I found that my improved SSS shader worked with the lowest render time.
One last tip: Use adaptive sampling:
This allows world backgrounds to render instantaneously, and most other materials to only render until the noise is low, reducing render times.
Note: This feature is in Blender 2.83+ currently.


Cabinet Properties aren't showing up! Archimesh Broken?

You have to click on the left bottom side tab that pops up when you add a cabinet. Click on that popup tab called Cabinets and you will get your properties.


I took the liberty to simplify the provided answers.

  Leon Cheung-method:

Bevel Ctrl+B edges and use Clamp Overlap C while beveling.

Example:

  stacker-method:

Enable LoopTools Addon that comes with Blender.

Then, use: W > LoopTools > Circle - Even though sometimes you need to manually adjust some angles.

Example:


I realize this is an old question, but the best way I found for editing Mixamo's animations are these:

Create your own IK controls on top of it ( I usually import an already IK-rigged model into Mixamo, but you can apply IK to a fresh rig imported from Mixamo). For example, you can leave the rest of the animation as is, and just control the arm with your IK. If you've rigged the rest of the arms, legs, etc. then make sure to turn the IK influence down to 0 for these (otherwise the mixamo animation won't work).
Edit specific F-Curves. For example, to move the arm, you want to select either the upper arm or forearm bone, go to Curve editor, type "rotation" into the curve editor search box and try moving the whole curves up and down. You can also pick a point in time where you want to modify the movement, select a keyframe on the curve there, and move it up and down so that the hand's position is the way you want it. (enable proportional editing to also affect neighboring keyframes - otherwise your animation will only look right at that specific frame and snap right back at the other ones. You can also edit every single frame but I wouldn't do that, as it's too much work and you're bound to get jittery results)


Will using quads affect game performance?

Stick to quads for modelling, as that is what most modelling tools are designed for.
Either the game engine should handle triangulating the model, or it should be triangulated just before export from blender if that is not the case.

The only exception to this is very low polycount assests where optimising the use of triangles is important (to get the right shape with fewer polys, not many games are going to need much of this though). In this case, you will probably want to switch to modelling directly with triangles at some point during the modelling process.

Its worth noting that everything is actually triangulated when rendering anyway,  even for the viewport opengl render while you are modelling. It is just easier to use a quad representation for mesh manipulation.


Why is there a white circle when I try to move vertices?

The white circle is due to "Proportional Editing" being turned on. It allows artist to move one element - a vertex - and a falloff is applied to the adjacent elements - neighbouring vertices. You will only need to turn "Proportional editing" off to stop the other neighbouring vertices from getting transformations you don't need.

It can be toggle on or off by pressing O. Alternatively, the button is here:

The button appears in the UV editor menu as well. They're linked, turning on the button on in the 3D view will also turn it on inside the UV editor.


Figured it out.  This seems to work:
    def modal(self, context, event):

        for area in bpy.context.screen.areas: # iterate through areas in current screen
            if area.type == 'VIEW_3D':
                area.tag_redraw()


Reading boolean values from file always return "True"

instead of casting to a boolean you can use them in an expression:

file = open(path+str(own)+'.txt','r')
line = file.readline().split(',')
own['pink'] = line[0] == "True"
own['red']  = line[1] == "True"


How do I make a separate mirror copy of an object (and do I need to?)

Use aplied mirror modifier, after! go to edit mode, in edit mode, go to mesh -> Separate Loose Partes! after! Go to object mode, and press in "new" object! and object -> set origin -> origin to geometry


Preventing the "Indirect Lighting" setting in Blender Internal from making the entire rendered image black

This is no longer a problem after upgrading to Blender 2.76b.


Randomize particle rotation on only one axis

Enable "advanced".
Enable "rotation".
Choose the axis you want to be up (Y of the model will be along the choosen axis).
And "randomize" the phase.


Blender decided to rotate it this way, you just have to select this face in the 3D view, then rotate it 90° in the UVImage Editor.


How can I reduce polycount without using decimate?

There are some but they'll all require some tweaking.  Investigate Decimate further, because there's some angle-limited options in there that are pretty good, and don't destroy the mesh as much, and if you can get it to do it for you then it'll be far less work.

However if you're set on not using Decimate then you may instead have to do it by hand.

Start selecting edge loops you don't need and dissolving them, as well as collapsing verts and edges wherever you think you can get away with it.

If you'd rather start from scratch as it were, you can make a new mesh and shrinkwrap it to your current one using the Shrinkwrap modifier.  Extrude sides, add new vertices, etc.  This way you can put topology exactly where you need it, and exactly how much of it is necessary and no extra.  This process is called Retopology and there's a lot of more detailed information out there available with a bit of searching.


How do I create a material that emits light based on how much light hits it?

This is how every material works:

Light hits material
Light might get absorbed by material (some wavelengs) and turned into heat
The rest of the light is reflected into different dirrections (it is diffused, reflected, refracted, bounces inside volume, etc.)

So the answer is easy, if you need to double the light that comes off the surface, you just add 2 shaders together (with add shader). This will break the energy conservation, but that is what you want.

If you need to emit the light in all directions, add white diffuse shader to your material.
If you need to emit the light directionally (as if bounced off of mirror), add white sharp glossy to whatever material you have. You can alter the sharpness of the light with rougness and also direction by manipulating the surface normals.

It is very possible that you can get some strange results.


Overview:

As far as I can see, your rain is made by using Particle System, so you will need to turn off Wind under Field Weights for it or for any other object you don't want to be affected by this Force Field.


MHX2 Import addon in Blender preferences

See the installation instructions at https://bitbucket.org/ThomasMakeHuman/mhx2-makehuman-exchange

You only need to copy the import_runtime_mhx2 subfolder to the addons folder, not the entire archive.


Beside what Mr Zak said, the only (crappy) way is to use the "bisect" tool in edit mode on each object to be "cut", using the box as reference, of course cutting in ortographic front/left/top mode. That cuts yor geometry (even without faces), adding new vertices along the cut edges, so that, later you can delete unwanted geometry outside the reference box...

The bisect tool is crappy, too, it has no way to keep straight, and is not affected by snapping, too. Again, if your cuts are not "perfect", your only hope is to use the snap tools after the "bisection", aligning the new vertices resulting near the box limits, to align them to the box vertices...

If not clear, I can make some reference image...

[edit] here you have the whol (crappy) sequence:

I started from a simple test setup but similar to your case, I hope:

seen from the side

so if you select the grouped green shape (this is only 1 mesh I just added a group to make it green like yours and also visually show it better) in edit mode, acting from the basic side view (ie: not in perspective mode, but ortographic, since you have to cut straight lines "by hand"):

You can select all the mesh (A key) and use the mesh>bisect tool.

Once you select it, you have to drag a straight line (you can start it from anywhere, I chose the intersection of green and orange lines, of course).

in the above image I angled it a bit for you to see it better, but you have to keep it straight, and drag it until it "cuts" also the bottom green/orange cross:

as soon as you release the left mouse button (LMB) the cut is set, and your mesh (also if has no faces) is cut, and new vertices made along the cut on all edges, as you see below, from an angled view.

of course you could be not as much precise cutting by hand, but you could always use now the snap tool set as you see below

then align those vertices (all together or even one by one) to your "limits box" (the orange circle hints that the selected vertices are aligned to the enclosed vertex of the "limits box"). I dragged them on the X axis in the example, and pressed the CTRL key to "snap" them until the orange circle confirms the snapping:

after doing this for all edges needed, you just need to delete "outer" vertices:

and you get something similar to what you needed, I hope:

...phew! :) what a crappy tool, I know...


How to make material from multiple objects appear as one. Ignore interior faces?

This should probably have been a comment, but I can't create those for now...

If you want to combine objects while eliminating the interior surfaces, the boolean 'union' operator seems the most appropriate to combine your circles. This operator removes internal faces (creating vertices where needed).
It's probably going to be quite fastidious to do, unless you can do it in stages where you combine a few tori, and then duplicate those units (e.g. create units of 4 red circles and one purple).


It looks like you forgot to enable your subsurf modifier by clicking the eye icon:

Right before then he enables the subsurf modifier, which causes the smooth subdivided interpolation of the mesh you are seeing.

Note that since the subsurf modifier is a modifier, you can enable it and disable it whenever you want without having to worry about doing it before or after various modeling operations. In other words, you have extruded it correctly, it just won't display the subdivided mesh until you enable the modifier.


Copy Location constraint is applied to all bones in armature even though I want to apply a different constraints to each bone

You have given an Object Constraint to your armature instead of a Bone Constraint to your bone (those are 2 different tabs in the Properties panel).


How to render a curve without creating meshes?

You could use OpenGL render (the button in the 3D View header) in Wireframe view mode. Every curve is rendered as a line without the need for any beveling. Animations can also be OpenGL rendered.

It is very fast. But there is no possibility to set the line width. It's always 1px.

To support transparency you have to set the shading mode to GLSL (press N in 3D View and look for Shading).


First, give each of your objects a white volumetric emission shader.  The strength doesn't really matter that much as long as you use the same material on every object so the relative density is consistent.

For the objects themselves I am using a collection of Metaballs.  Meta-objects will "blend" into each other similarly to what you are describing.

Now set set your background color to black and render.  This will result in the following black and white map.

Next jump over to the compositor to remap this to the color gradient you want.  First plug the render into a Normalize node to remap the range of the render to [0,1].  Now run that output through a Color Ramp node and set up whatever gradient you want.

I also found that it gives a result closer to your reference images if you also add a small amount of blur.

The result looks like this:


Is there a way to copy the mesh of a cloth sim at a particular point in time as an individual mesh?

Create a copy of the cloth mesh, run the animation, stop it where you want and apply the cloth modifier.


How to get all "collections" name in one line output from "for loop" (python)

bpy_collections.
Blender uses a collection that can be accessed like a dictionary (string key) or like a list (integer index)
The name of the object in the collection is also its keys. For a collection the names of all objects in the collections can be gained quickly via the collections keys.
D.collections.keys()

(D.collections.values() is the values, and .items() the key, value pairs.
Or via list comprehension.
[c.name for c in D.collections]

Or lastly using a for loop
>>> cols = []
>>> for c in D.collections:
...     cols.append(c.name)
...
>>> cols
['Collection 1', 'Collection 1.001', 'Collection 1.002', 'Collection 1.003']

Note: could have also used cols = list() here since list is a python type. In as much as can define it as something else list = "something else" it's not recommended practice


I'm not at my pc at the moment, so I can't test it, but I can point you in the right direction, I would use a colorramp-node and mask out the dark squares so they are transparent, then use the geometry-node (docs.blender.org/manual/en/latest/render/shader_nodes/input/…) to create a mask for the position, use another colorramp to set the threshold, and then blend between the original and the transparent texture using a mix-node and the factor comes prom the mask. I hope that helps and I'm sorry that I can just be theoretical at the moment. All the best – Marco Vitale


How to remove unreferenced UV Coordinates from a Texture

The geometry is reflected on the UV. If you mention it is junk, probably delete the mesh junk park associated with it as well. Otherwise, re-unwrap Uvs.

I read this question 3 times. I know what you´re having: shadow uvs. Yeah, bisecting is a special boolean case. I´d strongly recomend you re-unwrap. It will only take a second. Baking textures: yes, you can do that as well, you´ll also get the old UV set. Got to object properties> vertex groups> Uv coordinates, delete them both vertex groups and coordinates. Then Un-wrap. Then bake old bisected to new unwrapped. Should work out of the box.


Material not displaying on array objects

In texture the coordinates node, you have it set to object, the scale then refers to the original object and doesn't get passed on to the ones created by the modifiers. Effectively you now have a bigger object and the texture doesn't cover all of it, and also the center of the object is now in a different place.
If you UV unwrap the original plane, then the texture will follow on the object created by modifiers.

To get an accurate image of what your textures look like switch to "rendered" view on the viewport.


How to use flat colors to determine how a scene looks? I want no shadows just colored shapes

Basically, toon shaders for all the gears. Some depth of field and the most important camera setting: Orthographic. Then my sun casts no shadows. Add vignette in Compositing and that's pretty much it.


GIT/Development builds:

The Buildbot:
There is a buildbot that builds from the git repo daily. You can get git (development) builds for all operating systems that blender supports here.
Compile from source:
Another option is compiling blender from source, see the wiki. While this may seem like a lot of effort, once its setup, it can be less trouble then having to continually download large files, and you can test new features minutes after they're committed.

Release candidates:

You can get past releases and current test-builds/release candidates here.

Linux:

There are some additional options for linux besides GraphicAll.org and the ones listed above.

Ubuntu:
You can use a PPA such as the irie PPA. (See this question on AskUbuntu for instructions)
Archlinux:
The blender-git package in the AUR


Have a look at the camera icon of your door object in Outliner. If it fades in like this then it won't be rendered.

You can turn it on with a click on this stuff.


Why does a material created in Substance Alchemist look completely different when imported to Blender?

This quick PBR material setup reference may help you. It's based on Allegorithmic Substance textures.


How to combine row + columm in a pie box?

The .split() is meaningless for pie menus, it has no effect. When you assign another item to the pie it will be at another position (so top).

To fix it you need to group everything inside a column and create the gap with .separator():

    # ...
    group = pie.column()

    box = group.box()
    row = box.row()
    row.prop(mesh, "use_auto_smooth")
    row.prop(mesh, "auto_smooth_angle", text="Angle")

    group.separator()

    box = group.box()
    box.operator("mesh.faces_shade_smooth", text="Mesh Smooth")
    box.operator("mesh.faces_shade_flat", text="Mesh Flat")
    box.separator()
    box.operator("mesh.normals_make_consistent", text="Normals Outside").inside=False
    # ...


How to copy bone animations, non-mirrored

Try this. Change your Timeline at the bottom of your screen to Dope Sheet. Next, select the keyframes from your east bone X and duplicate them to your other limbs. You should see under the Dope Sheet Summary each of your limbs. This has worked for me when I need to copy my animations to other limbs. Hope this works for you!


Generate video sequencer project from a script

I use the following script to import my mts video files into a new project.

Use it like: blender --factory-startup --python script.py -- --save="path\project.blend" -m="folder_with_mts_files_relative_to_blend_file" -n="optional_second_folder".

It imports a "Textmarken.txt" (Audacity Text Labels) as well if existing and sets up the view in Blender as well as some Video Properties for my project as I need them. It should help you well to see what's possible and adapt it to your needs. It most likely does more than what you want to achieve, but it will for sure guide you into a proper way...

import bpy
import os
bpy.context.user_preferences.view.show_splash = False
channel = 1

def read_labels_data(filepath):
    f = open(filepath, 'r', encoding='utf-8')
    data = f.readlines()
    data = [w.replace(',', '.') for w in data]
    f.close()

    scene = bpy.context.scene
    default_frame = scene.frame_current

    override = {'region': bpy.context.window_manager.windows[0].screen.areas[2].regions[0], 'blend_data': bpy.context.blend_data, 'scene': bpy.data.scenes['Scene'], 'window': bpy.context.window_manager.windows[0], 'screen': bpy.data.screens['Video Editing'], 'area': bpy.data.screens['Video Editing'].areas[1]}

    bpy.data.screens['Video Editing'].areas[1].type = ('TIMELINE')

    print('---Import Audacity Labels to Timeline Markers---')
    for i in range(0, len(data)):
        seconds = data[i].split()
        frame = bpy.utils.time_to_frame(float(seconds[0]), fps=None, fps_base=None)
        scene.frame_current = (frame)
        bpy.ops.marker.add(override)

    bpy.ops.marker.select_all(override, action='TOGGLE')
    scene.frame_current = default_frame

    return {'FINISHED'}

def import_function(save_path, mts_path1, mts_path2):
    scene = bpy.context.scene
    base_path = os.path.split(save_path)[0]

    # Clear existing objects.
    scene.camera = None
    for obj in scene.objects:
        scene.objects.unlink(obj)

    if save_path:
        save_path = os.path.abspath(save_path)
        try:
            f = open(save_path, 'w')
            f.close()
            ok = True
        except:
            print("Cannot save to path %r" % save_path)
            import traceback
            traceback.print_exc()
        if ok:
            bpy.ops.wm.save_as_mainfile(filepath=save_path)

    # Set up GUI - open screen "Video Editing"
    bpy.ops.screen.screen_set(delta=1)
    bpy.ops.screen.screen_set(delta=1)
    bpy.ops.screen.screen_set(delta=1)
    bpy.ops.screen.screen_set(delta=1)
    bpy.ops.screen.screen_set(delta=1)
    #bpy.data.screens['Video Editing'].areas[0].type = 'INFO'
    #bpy.data.screens['Video Editing'].areas[1].type = 'TIMELINE'
    #bpy.data.screens['Video Editing'].areas[2].type = 'SEQUENCE_EDITOR'
    # Change Graph-Editor into Properties:
    bpy.data.screens['Video Editing'].areas[3].type = 'PROPERTIES'
    #bpy.data.screens['Video Editing'].areas[4].type = 'SEQUENCE_EDITOR'

    # PROPERTIES - Area
    override = {'region': bpy.context.window_manager.windows[0].screen.areas[2].regions[0], 'blend_data': bpy.context.blend_data, 'scene': bpy.data.scenes['Scene'], 'window': bpy.context.window_manager.windows[0], 'screen': bpy.data.screens['Video Editing'], 'area': bpy.data.screens['Video Editing'].areas[3]}
    presets   = bpy.utils.script_paths()[1] + "\\presets"

    # Set Video-Properties
    bpy.ops.script.python_file_run(override, filepath= presets + "\\render\\HDTV_720p.py")
    #bpy.context.scene.render.resolution_percentage = 100
    bpy.ops.script.python_file_run(override, filepath= presets + "\\framerate\\25.py")
    bpy.context.scene.render.antialiasing_samples = '16'
    bpy.context.scene.render.filepath = "//out"
    bpy.data.scenes['Scene'].render.image_settings.file_format = 'H264'
    bpy.data.scenes['Scene'].render.image_settings.color_mode = 'RGB'
    bpy.ops.script.python_file_run(override, filepath= presets + "\\ffmpeg\\h264.py")
    bpy.data.scenes['Scene'].render.ffmpeg.use_lossless_output = False
    bpy.data.scenes['Scene'].render.ffmpeg.video_bitrate = 4500
    bpy.data.scenes['Scene'].render.ffmpeg.gopsize = 25
    bpy.data.scenes['Scene'].render.ffmpeg.maxrate = 7000
    bpy.data.scenes['Scene'].render.ffmpeg.audio_codec = 'MP3'
    bpy.data.scenes['Scene'].render.ffmpeg.audio_bitrate = 64
    bpy.context.scene.render.engine = 'CYCLES'

    # Playback-Settings
    bpy.context.scene.use_audio_scrub = True
    bpy.context.scene.use_frame_drop = True
    bpy.context.scene.sync_mode = 'AUDIO_SYNC'
    bpy.data.screens["Video Editing"].use_follow = True

    # If existing, read "Textmarken.txt"
    marken = base_path + "\\Textmarken.txt"
    if os.path.exists(marken):
        read_labels_data(marken)

    # Sequencer Area
    override = {'region': bpy.context.window_manager.windows[0].screen.areas[2].regions[0], 'blend_data': bpy.context.blend_data, 'scene': bpy.data.scenes['Scene'], 'window': bpy.context.window_manager.windows[0], 'screen': bpy.data.screens['Video Editing'], 'area': bpy.data.screens['Video Editing'].areas[2]}

    if mts_path1:
        import_from(override, base_path + "\\" + mts_path1)
    if mts_path2:
        import_from(override, base_path + "\\" + mts_path2, True)
    bpy.ops.wm.save_mainfile()

    for name in os.listdir(base_path):
        if '.wav' in name or '.WAV' in name:
            print(name)
            # add all further wave files
            bpy.ops.sequencer.sound_strip_add(override, filepath=base_path + "\\" + name, frame_start=1, channel=channel*2)
            #bpy.data.sounds[name].use_memory_cache = True
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[name].show_waveform = True

    #bpy.ops.sequencer.view_all(override)
    # deselect all strips
    for seq in bpy.data.scenes['Scene'].sequence_editor.sequences_all:
        seq.select = False

def import_from(override, mts_path, muted=False):
    global channel
    print(channel)

    names = os.listdir(mts_path)
    frame = 1
    #print(names)
    names = sorted(names)
    for name in names:
        if 'MTS' in name and not '.lwi' in name:
            print(name)
            base = os.path.splitext(name)[0]
            avi = base + ".avi"

            # add original video strip to get the audio and delete the video again (you might omit the delete)
            bpy.ops.sequencer.movie_strip_add(override, filepath=mts_path + "\\" + name, frame_start=frame, channel=7 + channel*2)
            for seq in bpy.data.scenes['Scene'].sequence_editor.sequences_all:
                seq.select = False
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[base + ".001"].select = True
            bpy.ops.sequencer.delete()
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[name].mute = True

            # Add AVI files from AVS-folder (you might not need this)
            bpy.ops.sequencer.movie_strip_add(override, filepath=mts_path + "\\" + base + ".avs\\" + avi, frame_start=frame, channel=7)
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[avi].mute = muted
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[avi].channel = channel
            frame += bpy.data.scenes['Scene'].sequence_editor.sequences_all[avi].frame_duration

    # move first audio strip back down
    for name in names:
        if 'MTS' in name and not '.lwi' in name:
            print(name)
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[name].channel = 2*channel+1
            #bpy.data.sounds[name].use_memory_cache = True
            bpy.data.scenes['Scene'].sequence_editor.sequences_all[name].show_waveform = True
            break

    if not muted:
        bpy.data.scenes['Scene'].frame_end = frame

    # deselect all strips
    for seq in bpy.data.scenes['Scene'].sequence_editor.sequences_all:
        seq.select = False
    channel += 1

def main():
    import sys       # to get command line args
    import argparse  # to parse options for us and print a nice help message

    # get the args passed to blender after "--", all of which are ignored by
    # blender so scripts may receive their own arguments
    argv = sys.argv

    if "--" not in argv:
        argv = []  # as if no args are passed
    else:
        argv = argv[argv.index("--") + 1:]  # get all args after "--"

    # When --help or no args are given, print this help
    usage_text = \
    "Run blender in background mode with this script:"
    "  blender --background --python " + __file__ + " -- [options]"

    parser = argparse.ArgumentParser(description=usage_text)

    parser.add_argument("-s", "--save", dest="save_path", metavar='FILE',
            help="Save the generated file to the specified path")

    parser.add_argument("-m", "--mts_path1", dest="mts_path1", metavar='FILE',
            help="Open all MTS-Files from this path")

    parser.add_argument("-n", "--mts_path2", dest="mts_path2", metavar='FILE',
            help="Open all MTS-Files from this path")

    args = parser.parse_args(argv)  # In this example we wont use the args

    if not argv:
        parser.print_help()
        return

    # Run the import_function
    import_function(args.save_path, args.mts_path1, args.mts_path2)

    print("batch job finished, done")

if __name__ == "__main__":
    main()


U-shape waves with musgrave texture node in cycles

Ok, I was able to get the scaling by putting a Mapping node before the Separate XYZ, so if you use this node setup:
I played around with the location and scale and power options getting this result:

Which sounds like what you are looking for.


Why can't I make item of clothing in the MakeHuman model?

Here's a imported MHX character from Makehuman.

It is already rigged, so the mesh of the skin (which is just a surface) is somehow controlled by several handles.

There are a some ways in which a mesh can be rigged. In this case the character was built with an Armature.
We can see in fact that the skin object (see the picture above for reference) has an Armature Modifier pointing to the armature (the top object of the hiererchy).

Every movement of the armature will be followed by a movement of the skin as defined by the armature's properties (bone weights, vertex groups, etc...).

When you switch from Object mode to Edit mode, the modifiers by default are not shown, so the skin doesn't follow the armature's deformation anymore. The mesh can be probably found near the origin in resting position.

You can edit the mesh "in place" by enabling the modifier visibiity for edit mode and adjusting the cage (see enabled options near the cursor)


Menu not showing up when python script is run

I just needed to add the following line to the end of the python script
Thanks goes to @brockmann for this.

if __name__ == "__main__":
    register()


BGE, logic bricks, setting up a timer (that reverses at some point)

Logic bricks are best explained with an image :

the basic idea is that instead of adding 1 to your “timer” you add an “increment” property.
You then switch this "increment" to -1 when it reaches 4 and back to 1 (effectively +1) again when the “timer” value is back to 0

to switch the "increment" property from +1 to -1 I do some fancy math (inverting the value and doubling it)

For a simpler version, you could also do it with 2 separate logic flows like here:


Extrude and subdivide without using tris

Here are a couple of ways to increase vertex count between edge loops using all quads.

And a quick trick for the right one using inset.

Set face select mode
Select two faces at the end you want to expand loop cuts.
Press I and inset a small amount
Select next two faces and press Shift R
Repeat step 4
Select all new internal faces
press Shift R
repeat 6 and 7 a few times
Set vertex select mode and box select the bottom vertices and delete

If you have a fully round mesh like your dress you can get around this step if you apply the mirror modifier and disable boundary in the inset options when doing the first inset. You can then delete half the dress and re-add the mirror modifier.

I now have a mesh that starts with 5 vertices at the top and ends with 37 at the bottom.


Images not displaying correctly with transparent objects in Blender 2.80

This looks like a bug related to the "sorting problem".  It appears as if image empties are being alpha blended to the color buffer after all regular Alpha Blend objects, so they always appear on top.

Two workarounds:

You can switch the blending mode from "Alpha Blend" to "Alpha Hashed".  This will give you a really noisy blend, but it gets the transparency right.
You can enable the "Import-Export: Import Images as Planes" add-on and add your image using "Add -> Image -> Images as Planes".  This adds the image as a regular plane mesh, and it seems to behave correctly even with "Alpha Blend".

Given that image empties can't be rendered anyway, as far as I know, "Images as Planes" is probably the best solution if you actually want the image to be a part of your scene.


Create a shower hose with correct physics

I believe the Softbody Simulation won't give you enough control over the movement. Here is an alternate method using a rigid body simulation.

The flickering is caused by the gif compression and not by a simulation error artefact.

It uses a chain of rigid bodies like in lemon's answer.

Enable the rigid body world.

Add a cylinder, make it a cylindrical rigid body. Then duplicate it. ⇧ ShiftD

Create an empty and place it inbetween the cylinder rigid bodies. Make it a rigid body constraint. Set the type to Point and select the two cylinders.

Create another rigid body constraint (on another empty): a generic spring. Enable the springs you need. I would use a very high rotation damping value, since a hose wouldn't wobble around. [0.9999]
I parented the generic spring constraint to the first point constraint, and the point constraint to the first cylinder, but this is just for easier visualization. The point constraint acts like a spherical joint between the two cylinder and the spring pushes the cylinder back to their original positions, ensuring minimal bending.

Create more cylinders, constraint and chain them. They're now ready to be simulated.

Note, how the twisting of a single joint in the chain influences its surrounding joints.
You can now transfer with movement to an armature with Copy Transforms constraints.

You can also connect it to a curve using many hook modifiers. The drawback of this method is, that the rotation of the rigid bodies is not used.


Following @Gordon Brinkmann's comment, in Blender 2.9x, using the 'Fast' Boolean option, (the modifier assigned to the plane,) it seems to work OK, here:

...across the angles.

But 'Exact' seems to fail; it includes the volume in the cube behind the plane's normal.


Blender doesn't recognise Middle Mouse Button?

With the normal 2 click mouse you can pan and rotate.
Go to user preferences and follow the settings given in image below

To rotate the view, hold the Alt key on the keyboard while pressing the Left Mouse button and moving the mouse.

To pan, hold Alt and Shift keys while pressing the Left Mouse button and moving the mouse.


How to hide a few objects of a multiple combined object cloth simulation?

What about adding some light force field (for example: wind) coming from the inside of the bag, just to avoid the collision of particles with the bag itself?

Here's a tutorial to manage the overlapping particles in Blender, not sure if it can help you.

You can also try to use the shader Particle Info Node, trying to identify the particle ID and setting a custom shader node (Transparent for example) for these particles.


Make sure you have "Selected objects" enabled when exporting the FBX file, otherwise all objects including hidden objects and objects on another layers get exported in the same file. Besides that the only explanation for multiple meshes per 1 exported mesh is exceeding Unity's 64,000 vertices per mesh limit that causes your mesh to import as multiple segments.


Duplicate meta-Ball with Animation Nodes

Lets say you have an animation of wiggled balls like this:

If you want to instance this animation 10 times, compose matrices from their transforms and replicate them based on the transformations of the second-level instances using the Replicate Matrices node. You should, of course, increase the amount of instances from $n$ to to $10\cdot n$ as follows:


Okay, so i found the problem i had if anyone interested... it had to do with my lighting. i guess for smoke simulations you cant use planes with a emmision node property. i had to use actual lamps or sun lights to avoid noise, but i still cant get it around my head how that works.

Thanks.


Since I had no luck with your file I created someting compareable.
Getting this working is tricky. You need to find balanced parameters most important are mass and sensitivty.
A mass of 100 is way to much and sensitivity should be > 0, e.g. 0.01 (probably blender units).

With a mass of 1.0 the simulation breaks after 90 frames:

When the mass of the second ring only is increased to 2 it works as expected.


Blender Internal Rendering half of the image

Fixed it, it looks that when i used Cycles to render the office I used volumetric lights, that means a giant cube covering the render. The solution? deleting the mesh that has the volumetric material.


Use the Fill Tool in the 2d Image Editor and you can then use the Thresh hold setting to dial in your desired tolerance. This threshold feature is not possible as of yet in the 3D view in Texture Paint mode, as it is a different process for painting under the hood. I believe that google search should have brought you to a thread here if I am not mistaken(I made that picture).


How to add pie menu so it will load next time I start with blender

load py from preferences addon tab. Then activate add on.


A more procedural workflow suggests the use of Splines to create the shape. Moreover, Spline UV maps can be used to create the pattern you are looking for. First, model the spline and give it a full depth as follows:

Then enable Use UV For Mapping and utilize the modulo operator to create the pattern you are after. The value nodes control the number of lines along the spline and radially while the less than values control the depth of the lines:


You can select in the Preferences what type of group you want to be selected specifically:


How can I merge these faces more efficiently?

Either follow Shady Puck's technique or simply use Collapse Edge Loops operator

In Edge Selection mode use by default Alt + Mouse Select to select a full edge loop, then press X > Edge Loops


Is there an equivalent of a cage for Blender Internal Render?

No, there is no option to use a custom cage for baking with the Blender internal engine. The closest you can get is the "distance" setting, which will sort of simulate a cage.
From the Manual:

Select to Active
Enable information from other objects to be baked onto the active object.
Distance
Controls how far a point on another object can be away from the point on the active object. Only needed for Selected to Active. A typical use case is to make a detailed, high poly object, and then bake it’s normals onto an object with a low polygon count. The resulting normal map can then be applied to make the low poly object look more detailed.


Project Paint is a Blender Render feature that doesn't appear to work when using Cycles. It is also an old way of texture painting.

In Cycles you need to add a material to the object and have an image node that defines what image is to be used to receive the results of texture painting.

Rather than using project paint you should try painting with a texture, I am referring to using a texture with a paint brush while in texture paint mode. The texture can be an image or any other procedural texture available in blender.

Once you have a texture setup, you choose the texture and set the brush mapping to Stencil then the texture will be overlaid in the 3dview. You can move the overlay with the right mouse button and rotate your model as usual, when the texture is in the place you want it to appear you can paint it on your model. The overlay clearly shows where the texture will be placed on your model.

While right clicking easily moves the overlay around, you can also use Ctrl-click to quickly rotate the overlay and Shift-click to scale the overlay to get the texture right where you want it to appear.

This technique works just as well in both Blender Render and Cycles. The overlay feature of texture painting was added in blender 2.67


Is chromatic aberration possible in blender

You can fake Chromatic aberration in the Compositor.
Just add the Lens Distortion node and adjust the Dispersion value.


Movie Clip Editor Graph editor: How to edit single motion tracking keyframe?

Why do you need to move them? The important thing to understand here is what exactly those graphs represent: they are the speed at which the tracker is moving in an axis. They do not represent placement in x and y coordinates. So if you affect one, the speed at which the next tracking point is moving will also be affected, as the speed is relative to the speed of the previous frame. Notice how they are inversily proportiional?
More info here: Motion Tracking. What do the graphs represent and how are they useful?
To view the motion as coordinates you can create empties out of the trackers to view in 3d space. The tracking constraint can then be converted to f curves and then the motion will be just like regular keyframes in the graph editor
Bake Follow Track constraint to f-curve?


The Checker texture is 3D. It divides the given texture space into blocks. The Brick texture is 2D. It's calculated in U and V, but just projected through W.

So you can map the checker in a 3D space, (here, Object space) but the bricks need some kind of mapping onto 2D surfaces to look like bricks. The default UV map of a cube will do, here.

If you'd like some kind of procedural mapping that rotates the brick texture to line up with surfaces without an explicit UV map, you can use an approach something like this one


How can I set a parent of an object in the BGE using python?

Simple:

import bge

cont = bge.logic.getCurrentController()
own = cont.owner
scene = own.scene

objA = scene.objects["objA"]
objB = scene.objects["objB"]

objB.setParent(objA)

setParent(parent, compound=True, ghost=True)

Sets this object’s parent. Control the shape status with the optional
compound and ghost parameters. In that case you can control if it should be ghost or not.

parent (KX_GameObject) – new parent object.
compound (boolean) – whether the shape should be added to the parent compound shape.

True: the object shape should be added to the parent compound shape.
False: the object should keep its individual shape.

ghost (boolean) – whether the object should be ghost while parented.

True: if the object should be made ghost while parented.
False: if the object should be solid while parented.

Source: Blender 2.79 API Documentation, bge.types.KX_GameObject section


How to control materials on the Brick Texture? (Blender 2.8)

Don't connect sockets like that. Yellow outputs go to yellow inputs. Green to green and so on. Green is for shaders. The material output node is expecting a shader (green), not a texture in RGB (yellow).

Read:

What is the meaning of the color of the node sockets in the node editor?

and

Cycles - (Shader) Nodes - inputs outputs - What are the exact data types?

To have three different Shaders controlled by the brick texture the you can do the following: Use pure black (0) and white (1) for colors 1 and 2 in the brick node and either black or white for mortar.

First let's look at the output of the brick texture: black and white bricks (and some mixture depending on the value set in "Bias")

We want could use that value information as the fac to mix two different shaders Yellow Bricks and Red Bricks:

What were white bricks are now Red ones, and the black ones Yellow.

Now let's examine the contents of the Fac output from the Brick Texture:

That is the information of the "Mortar"

You can use that information to control yet another mix shader.

This way you can have a completely different shader for the mortar as well.

Additionally you can also use the Mortar as displacement.

If you need more separation between the color 1 and color 2 (so that there are less bricks that are a mix of the two colors) you can add a color ramp in between the color output of the texture and the first mix shader. That way you can control the contrast of the image for the mix.

From there on you can do whatever other adjustmets you want.

In case you are wondering... why are we connecting yellow outputs on gray input sockets? Doesn't that contradict the very first sentence on this answer? Yes there are cases where you can break the rules a little.

Yellow sockets are Red, Green, and Blue  color information (RGB)

Gray ones are a single channel (greyscale) info.

By turning the color 1 and 2 to black or white we are creating grayscale information, so that can be used in a gray socket.

Likewise if you plug a gray output socket to a yellow (color) input, all you will get is monochromatic information.


Creating a "halo" effect for a material in cycles?

This kind of effect is usually created in post processing.  In Blender's compositor I found that the Filter > Blur node gives a result quite close to what you are looking for, though the Glare node may also work.

Just go the the Node Editor view, switch to compositing nodes, and drop a Blur node in between the Render Layers and Composite nodes.  I found that using Fast Gaussian seems to produce the best looking effect.

To get that even wider glow you can add a second blur node with a much larger blur and mix it with the smaller blur.  Set the mix mode to Add and adjust the Fac slider to suit your tastes.

Click to enlarge.

For the actual mesh I just used the IvyGen technique outlined here with a very strong volumetric emission shader (and no surface shader).


Can't view rendered Image Sequence over movie clip in compositor or VSE

What I get from your nodes and description is, that you want to overlay your rendered image sequence from the 3D view onto a movie clip. Unfortunately, the red marked clip is not the render from the 3D view, but in fact as you noticed correctly, an image sequence of your movie file.

Why did this happen?

When pressing the Animation button to render you sequence, Blender check first if there are clips in the VSE. If there are, Blender will render these clips only. If there is nothing to render in the VSE, the compositor nodes are checked. If you are using nodes, Blender will render the nodes only. If there is nothing in the compositor and the VSE, Blender will only render the 3D view.

I'm guessing you had the movie clip in your compositor, when you tried to render the 3D Viewport animation. Thats is why, the composite node got rendered into an image sequence (which is connected the the movie file).

In order to render your 3D Viewport image sequence first, disable the Sequencer and Compositing rendering in the Properties Panel.

Render the image sequence. Your png files should look correct now.
Enable Compositing again. You will have the correct preview in the Compositor. When you render, the composite node will get rendered into the output. That's why you have to change your image sequence now, because you don't want to overwrite the 3D Viewport image sequence.

Viewing the 3D preview in the compositor or VSE

Even though pre rendering the 3D image sequence is useful for realtime feedback, you can simply add the 3D render into the compositor by adding a Renderlayer node. Use it instead of the prerender sequence.

The same can be done in the VSE by adding a Scene strip.


Related answer.

To only gain the reflection and refraction in the sphere, you have to simulate your environment.

Roughly model the shapes of your environment.
Assign a material to the environment object. Use and Emission BSDF. Input the background image as a texture with Window Texture Coordinate.
In the viewport, the image will be mapped to the object according to its position in the (2D) window. From camera view, this will look correct.
Since the camera is not supposed to render the environment object, turn off Camera in the object cycles settings.

From BlenderGuru:

  Just like with the Camera coordinates above, the Window coordinates
  are not used very often. In the past I’ve used this to stick camera
  footage onto a plane behind my scene, so that some glass materials
  would correctly refract what’s behind them and the models would be
  more accurately lit by the environment in the footage, but that’s
  about it.

The render will be more realistic if you add more geometric and have more than just the window frame textured since the reflection of a glass sphere will reflect 360°.


Rendering parts of an animation in different computers

Render as image sequence on each computer, then encode those frames as a video file later.

open the project on both computers and just change the range of frames each computer should render.

Never render to video for two reasons:

If the computer crashes you will loose all, if you render as separate images you just loose the last rendered frame.

The second reason is that by having an image sequence you can then find the correct encoding settings without having to start from scratch.

Also,  if you render on different computers as video then you have to re-encode to make the files a single video. Every time you encode you loose quality


I'd do it backwards:

Create a circle
Use Box Select to delete the lower half of the circle
Select all of them and extrude upward
Flatten the upper half with SY0RETURN (might be another axis for you)
(alternatively just extrude the side verts, select everything and fill the whole thing with F)
Extrude the entire shape to give it depth.

There's another way of doing this....

Take a cube and give it more resolution. Either with a Loop Cut or by subdividing the lower edges.

Then use the Proportial Editing Tool, set the falloff to spherical, select the middle edge and move the mouse up, restricting it to one axis. Doesn't always give a perfect circle though. More like an ellipse.

Luckily there's another way of doing this...

Again use a cube that has enough resolution at the bottom, put a cylinder under it (use one with enough verts, 1024 segments are fine) and use a Cast Modifier on the Cube. Apply the modifier and get rid of the cylinder.


Loop cut not working on my blender project?

Press Z to see your object by transparency, you'll see an inner face, you can't create any vertical edge loop because of this inner face: with this kind of topology Blender can't guess what face the edge is supposed to go through. So just select and delete it.


How do I keep animation speed over multiple keyframes?

Create a path using "poli" type curve
parent the cube to the curve
use path animation and choose the number of frame based on the path total length to get the desired speed

Note: check the Follow option so that the cube rotates along the curve


Is it possible to combine 2 or more textures VIA - BelnderKit add-on

Thanks to Nascent for the awnser.
You just add a new image texture node. Click new and name it. Then add that to the 'fac' of the MixRGB node. Then all you have to do is go into the texture paint tab and make sure you have your new texture selected (I named mine Dirt_Path_PAINT) and draw over your texture in the UV section or for easy use right in the viewport!


on fbx export my model gets destroyed -> see image. why and howto resolve issue?

This answer is valid for FBX 6.1 ASCII.

You have non ASCII characters in shapekey names, which the fbx format apparently doesn't support.

As it seems, two characters can't even be displayed in my Blender.

Rename these shapekey names with ASCII characters only.
You also have some missing weights on Body.

Exporting in FBX 6.1 ASCII works correctly.


how do I organize the materials? joining two seperated objects after editing

Blender only allows you to edit one object at a time, so yes you can only see and select the vertices of one object.

Every face in a model can use a different material, if you join multiple objects, the combined object will have multiple materials available and each face will continue to use the same material it used when it was in a separate object.

In edit mode you can assign a specific material to the selected faces.

If you join the multiple objects into one, you can use the by material option in the separate menu to split each into it's own object based on the material it uses.

So yes you can join multiple objects and they will keep the materials. You can easily re-separate them. You can also create one object, assign different materials to parts as you model and then separate them based on the material when you are finished.


Alternative solution to switching GPUs

Use render layers! Just put foreground objects in a layer and background objects in another, render (making sure you enable transparency), then combine the layers using the built-in compositor. This way you can also render a layer with more samples then the other, instead of rendering everything with high samples.


Boolean Modifier difference operation not working

One and half year later ....

First issue - "Clipping" from your first image - viewport glittering of overlapping two coplanar faces. On that place is face of original cube and newly generated face in the wall by modifier.

Modifier takes cube only as a reference for operation, so you have to hide cube manually to see Boolean result (like you did it by moving into another layer, or you can uncheck visibility in Outlines Editor.

For the second issue - difference cube from outside, but not inside ... you need to set some thickness to the wall.

From blender view, you are like in a volume of the cube (room). You can noticed that by display face Normal orientation. They are faced to outside, that is outer side of object for blender. To get a hole by Boolean modifier you need also for interiér generate faces with normal faced into interier.

Simple way (but depends on your model) is to add Solidify modifier before Boolean operation.


Connect two cylinders at the corner of a bench seat

Well it can be achieved with Bridge Edge Loops function:

Align 'end cap' polygons at the beginnings of the desired curve. The trick is to maintain same distance from the angle point
Select both caps and press W > Bridge Edge Loops
Tweak connection properties


Change focus on mist pass for getting DOF in composition

You can try inserting an add node between the mist pass and the color ramp, to "offset" the focused value. Tweaking the values, positive or negative, you should be able to set the knife pixels as focused and the rest unfocused. If you can post an image of your mist pass i can be more accurate on the answer.


If the model the t-shirt is on is moving and a collision object, I'm going to guess the movement isn't wind, but the effect of the momentum of previous movements staying in the system. I'd suggest posting your cloth settings, but I'm guessing you need to look specifically at the "damping setting" on the right side of the cloth settings.


he subdivision surface modifier is placed before the mirror. Invert them.

The reason: if before, subdivision surface will smooth vertices out of the mirror axis, so they won't join anymore.


How do I make a single face of an object a particle emitter?

You can make Vertex Group out of bottom face (create Group, select Face and hit Assign, without painting)...

...and use it to control Density under Particle System > Vertex Group.


Im not sure if i understood you correctly, but I try it anyways.
I used a Path with a Circle as a Bevel Object. Watch in the Path settings. The Bevel Circle is on Layer 2.

The workflow for Hook 2 Objects:

Select your Mesh
Shift+Select your Path
Press TAB to switch to Edit Mode
Select the Point of the Path you want to Hook to
Ctrl+H > Hook to selected Object
Done

Here is an example File. I hope I could help.


I'm all about the nodes too, but i'm also all about leveraging the power of Blender from inside Sverchok. (When it makes sense, and when it can offer perfomance boosts.) This also offloads the pesky "twist" Matrix calculations to Blender, and lets you use the Twist parameter on the Trajectory curves.

For now i started a discussion about this on our Issue tracker, because I think this technique can be wrapped into a single node and automated/parametrized.

What I did here was generate two Profiles using generator nodes (Ngon, and Circle) and output them using the PolyLine Viewer, i also made sure the profiles had the same vertex count and the vertex positions aligned to allow nice linear interpolation between the two shapes. Then I added a trajectory and copied it, and added the two bevel shapes to them individually

then the Objects In node imports both Curve Objects as Meshes, we separate the two meshes, and divide each mesh by the number of vertices of the Profile vertex count. This division results in a number which corresponds to the number of nodes/vertices in the original trajectory Curves. It also is the number of times we need to repeat each element of our interpolation range. so we go from

[0.0, 0.07, ....1.0]

to

[  0.0,  0.0,  0.0,  0.0,  ...
   0.07, 0.07, 0.07, 0.07, ...
   ...   ...   ...   ...   ...
   ...   1.0,  1.0,  1.0,  1.0  ]

We do that with the List Repeat node, and List "Delete Levels" (which is essentially a "Flatten List" node)

here's the blend


How to randomize holes in a mesh, like with a particle system?

What about using the Alpha channel on the texture? Create a random noise texture (or any pattern you want) and plug it in the Alpha channel. I think that the effect should be believable enough.

I would then add a simple bump map in addition to that, so the corners of the whole are a bit smoothed.

EDIT:

So obviously you need to play around a bit with the generated textures, but this is the way I'd approach it. Here is a sample:

This looks stupid because I didn't use a leaf texture or the proper model, but I think it would look quite good on yours, and it's completely procedural, so it will be randomly generated automatically and you can define and keyframe the size.

I've added a small gradient so the leaf gets browner closer to the wholes (you could blend this with a nice brown leaf texture), and a bump map, so the holes don't have a completely hard border.

This is the node setup:

Hope that helps.


How to limit grease pencil draw area to inside of closed curve?

This can be achieved by masking a layer by another one.
On 2.91 here's how i will do it :
1 : enable masking on the desired layer

2 : select the mask layer from a list

3: turn the mask layer invisible

Step 3 can be done by several ways, like turning down layer's opacity or as Gorgious said, setting the grey material as a holdout.
Note that there is a mask toggle icon next to the layer's names in properties and dopesheet areas.


How do I animate a character with dangling chain

You would need to enable rigid body from the physics tb for each chain link. Set the one you want to animate as passive all others to active. The collision shape must be Mesh.

Settings for the links:

To control the passive link by an armature you could add a Copy Location Contrained

If the chain breaks in the simulation increase the Solver iterations from the Scene / Rigid Body World settings and click Free Bake followed by Bake All Dynamics.

Demo .blend


Removing all meshes from a collection with Python

Don't think there is a simpler way (as you mentioned in the question).

Globally:

Get the collection
Iterate over mesh objects in the collection
Keep its inner mesh data
Remove the object

Then (optional):

Iterate over the collected meshes
Look if it has became orphean (no user)
If yes, delete it

Commented code:

import bpy

collection_name = "items"

# Get the collection from its name
collection = bpy.data.collections[collection_name]

# Will collect meshes from delete objects
meshes = set()

# Get objects in the collection if they are meshes
for obj in [o for o in collection.objects if o.type == 'MESH']:
    # Store the internal mesh
    meshes.add( obj.data )
    # Delete the object
    bpy.data.objects.remove( obj )

# Look at meshes that are orphean after objects removal
for mesh in [m for m in meshes if m.users == 0]:
    # Delete the meshes
    bpy.data.meshes.remove( mesh )


How to scale dimensions proportionally to a specific size?

As far as I know it can't easily be done on a single atomic operation unfortunately, but I generally use the following workflow.

To scale uniformly with precise absolute dimensions, in the Properties Area of the 3D View just type in the exact absolute dimension you require on the single desired axis.

Now check the resulting scaling on that axis, Blender will have calculated the appropriate factor for that vector. You can now copy-paste the value with Ctrl+C, Ctrl+V to the other axis so they all remain uniform.

Apply the scale afterwards if you desire with Ctrl+A > Scale while in Object Mode.


What's the bets way to get an atmosphere effect?

It's possible to do with Volumetrics and other effects, but generally not worth it for both render time and resulting quality. Your best bet would be compositing with Z pass (Z depth) or Mist pass. It would take some tutorials for in-depth compositor nodes for making it inside Blender, but overall the idea is: you render your scene image and another pass(Z or Mist)  - a black and white image which goes from black to white depending on the distance from camera to the most distant rendered object. Then you use that pass in compositing the final image with your rendered scene, either inside Blender Compositor with nodes or image editor (like Photoshop).