Blender 2.8 - Texture not showing up on material preview, neither exporting to .fbx file

Thank you very much guys! I didn't know i couldn't export more than one uv map on an .fbx file. Now that i delleted all the other uv maps, the face texture is finally showing up when i export the file. I really appreciated your help. Thank you!


You can do this easily using the Select Sharp Edges function.

Use Select > Select Sharp Edges and adjust the angle.
Now you can mark all selected edges as sharp

To turn all sharp eges into UV seams.

Select one sharp edge
Use Select > Similar > Sharpness and mark the edges as seams


Is there a way to group animations into one action?

There was (Blender 2.49) the option to trigger animations of all child objects via [child] flag at the action actuator. But there is really limited use on that.

No there is no way to have several actions of several different objects as one. The armature does that partly (animating different objects) but i guess this is not what you mean.

The way to go is to ensure all objects play there respective animation at the same time.

You can do that by sending a message e.g. "play cut scene A sequence 1". Each object involved starts playing on receipt of that message.

As all objects receive the message at the same frame the actions will play synchronously. Be aware there is no feedback (e.g. if one object is not playing the other objects do not know about it).


How can I make a plane's edges taper inwards?

While in Edit mode, select the plane and subdivide it, by pressing W>Subdivide. You can press F6 to adjust the number of cuts. Then, use the Proportional Editing tool, enabled by pressing O, or by going to the 3D View header, and set it's falloff to Sphere.

Now, select the center face/vertex and scroll the mouse so the circle doesn't contain the corner vertices and scale to taste.


Is there a way to generate an armature from a collection of points/vertices?

I would do it this way, requiring Blender and Blender Add-On: Sverchok and/or maybe Animation Nodes (!).

Supposedly all this can be done using Python Script, but for artist, maybe Sverchok or AN Animation Nodes is A LOT easier.

You start with some kind of data of point cloud. In CSV or whatever. I supposed you have recorded the data for each frame. I will start with just a single frame, this will be for the Rest Bones.

Load the CSV data into Sverchok via Text In node. Right away here, I am turning the point cloud into group of edges, merge, and this will be for the Bones, via Skin Modifier.

Poly Edge -> Skin Modifier -> Create Armature -> Bones! Magic!

Here, sometimes you need to Clear Parent for the Bones.

Next, we simply pipe in the animation data into the Pose Bone, frame by frame using Animation Nodes or Sverchok. Here is Sverchok way:

So.... that's pretty much it the basic idea.


How to properly paste Python function block into python console?

There is a solution, usually when I encounter this problem, I replace "TAB"'s with spaces. Here is the interesting thing, you can replace a "TAB" with any number of spaces. You could replace a TAB with a single space, or multiple spaces.

Now, for the second part of your question, any text editor that allows you to set "TAB" to spaces, so in "sublime text 3" which I use you would go to "view"->"indentation"->"Indent Using Spaces".

Here is the fun part, "TAB" with in a python file is not a problem for the python interpreter, it works fine. Its just an issue when you pasting to the command line.

Also, I don't know what your question has to do with Blender, this should be an S O question.


Particles render much larger than in viewport

The problem was that the size of my particles in "Viewport display" section and "render" had to be the same.


How can we create a Bar code with the Texture Node Editor?

waaow!! here is a zany bar code shader for eevee simpletons such as i


Volumes with space-dependent light intensity

You can use an Emission shader for the Volume socket of your Material output node, and give it a volumetric texture.

It's pretty easy for a 1s orbital, (n,l,m) = (1,0,0). (spherical symmetry, monotonic decay: it's not actually exponential in my example below):

Create a sphere, and assign a material to it like the one in the picture.

The first three nodes to the left (Geometry, Object Info and Vector Math>Subtract) will output a vector (x-x₀, y-y₀, z-z₀) for each x,y,z point in the sphere's volume, where x₀,y₀,z₀ is the pivot point of the sphere. The following node Vector Mapping can be used to scale the texture. These are the cartesian coordinates that will be used to define a scalar function, like a wavefunction.
The last four nodes to the right ("Math>Absolute, Color Ramp, Emission, Material output) will take the output of your scalar function and assign it to the volumetric emission, colored according to a color map (I've taken the absolute value, you might want to take the 2nd power, or to have different colors for the positive and negative values).
In the middle, you will need your actual scalar function. It can be any node, or group of nodes, that takes a Vector (blue socket) as input, and outputs a scalar (grey socket). In my example, I've used a Gradient texture node. Unfortunately, complex functions are not built-in in blender. You can, however, create a Script node that implements the wavefunctions (you will probably need numpy.polynomial.legendre)*

* I've never done this before, so I can't guarantee it's possible to just make python do the math. If it's possible, I think this wiki page is a good starting point.


In edit mode scaling, moving and any other manipulation is done via increments

It sounds like you have turned snapping on. Press Shift + Tab to toggle it off.


Knife project only cuts visible surfaces. How to cut opposite sides?

The option is available in the Operator box, bottom left in 2.8, on the bottom of the Tools panel in the previous versions.


Restore mesh data layers (specifically UV) after non-destructive Remesh modifier?

It looks like this is a known bug. For now, the below workaround does the job.

Hm. Okay. So I haven't found a way to restore mesh data layers onto any object which has an active Remesh modifier in its modifier stack.
But by abusing the "Caps" settings on an Array modifier (or similarly abusing a Boolean modifier), it is possible to non-destructively transfer the remeshed geometry onto a clean, empty object that does have the required data layers. From there, modifiers which require mesh data layers seem to work as usual.


Animated displacement of rigid body does not collide with other rigid bodies

many thanks for your help.

I actually did it in an indirect way, a few days ago, by using arrays of passive/animated rigid bodies and connecting them to the animated plane by using Shrink Wrap. This created a moving floor (up-down motion), that interacted with the active/rigid icospheres, giving the result I wanted. Many thanks for your help and I will try the suggested methods to see if they work too.


How to rig a Seatbelt? (Buckle passing through seatbelt)

You could do it with Lattice:

Bring back your belt to a flat plane:

Create a lattice,  in the Properties panel > Object Data choose its Resolution (here 2/1/5), in Object mode, scale it down, rotate it so that it frames the area that you need to tweak. Give your belt a Lattice modifier and choose the lattice as Object.

In Edit mode, move the vertices of the lattice so that it tweaks the belt the way you want. Parent the lattice to the buckle so that when you'll move the buckle, the lattice will follow and tweak the belt:


Strange photo appears when creating mirror

it's the standard "viewport shading > material preview" settings. it's a "nice" standard feature to simulate that your mesh in somewhere in a real place:

you can also switch the shading preview if you want using this toolbar:


It sounds like the viewport is no longer locked to the 3D cursor to me.

Press "N" to pull up one of the side menus, and switch it over to the view tab. Click on "View Lock" and check if "Lock to 3D cursor" is selected


Vertex color value has weird offset in value when assigned from script

Looking at the blender sources, the colors seem to get rounded.

static void rna_MeshLoopColor_color_set(PointerRNA *ptr, const float *values)
{
  MLoopCol *mlcol = (MLoopCol *)ptr->data;

  mlcol->r = round_fl_to_uchar_clamp(values[0] * 255.0f);
  mlcol->g = round_fl_to_uchar_clamp(values[1] * 255.0f);
  mlcol->b = round_fl_to_uchar_clamp(values[2] * 255.0f);
  mlcol->a = round_fl_to_uchar_clamp(values[3] * 255.0f);
}


How do I fix my upside down video, and make it so it is not compressed and choppy

It’s not “compressed,” that is a storage term. The video is “playing at the wrong speed.” This may have to do with frame rates. The video being upside down has more than one explanation since it was from a phone, but you can thankfully fix that quite easily. Check out the clip settings on the right to transform it and flip it over, or use a transform strip to do it. Note that you may have to flip it sideways as well to avoid mirror image effect. Look at those same settings for adjusting the video frame rate, or if all else fails use a speed adjuster strip.


Having trouble making a twisting animation more realistic

This might be a good place to model the band as a curve (with a rectangular curve Bevel object,) and use the shipped Animall add-on, which enables you to key-frame control-points, and their tilt values.
This animation is of a default Curve > Circle, subdivided once. The three vertices at each end are rotated in opposite directions, while the entire circle rotates through 90 to present the figure-of-eight to the camera. Animall permits the keying of tilts, rotations, locations of the control-points to keep everything more or less in shape.

(v2.91 .blend file)


Why is the color ramp in the compositor treating my transparent pixels as black?

...and yes, shame on me, big Blender community, i did not answer the question "why is the colorramp....", but hopefully it is useful for stillsleep and that's what he wanted to achieve.
If i understand you right, you want to

convert black to transparent

convert white to transparent

if yes, here is the node setup:
Original:

convert black to transparent

convert white to transparent

and just in case you wanna make both transparent, black and white, you can use this setup:


How to get list of bm.verts that belong to a deform layer?

OK I managed to find the values I needed by printing these variables:

# Layer Deform is the vertex group layer in bmesh mode.
layer_deform = bm.verts.layers.deform.active
if layer_deform is not None:
print('--- This is the deform layer info: ---')
    for vert in bm.verts:
        dvert = vert[layer_deform]
        print('vert index: ', vert.index, 'vert id:', vert,'vertex groups:', dvert.items()) #dvert.items gives you two elements: int of vertex group (I think by the order they were created added), and a 0.0 to 1.0 about the weight. If the vert doesn't belong to any vertex group, this dict will be emtpy. vert gives the BMVert in this format: BMVert(0x0000000012998B88)
print('--- End of deform layer info ---')


Combine a Mat map and a Normal map in Blender?

The answer is yes you can do that. I am assuming you are working in the Blender Render Environment and not cycles as their material workflow is quite different.
Attached is the file for your reference. The material is an old 3dsmax metallic material and the normals map has been generated using shadermap3.

For Blender Render workflow.
1. Create a new material on the material Tab on the properties panel.
2. Next go to the texture Tab on the properties panel.

Settingup Albedo/Diffuse Map
3. Select an empty texture slot and click on "New"
4. Select open and point to your Albedo map on your harddrive.
5. Under Influence Header make sure "Color" is checked.

Setting up Normals Map
6. Select another empty texture slot and click on "New" again.
7. Select open and point to your Normals map on your harddrive.
8. Under Image Sampling Header make sure "Normal map" Option is checked.
9. Under Influence Header make sure only "Normal" is checked.

Here on out you should be able to see the normals texture in the viewport in "Textured Mode". Remember to add some light source or else your scene will just be blackish and dark.

Happy Blending!


Selecting part does not seem on blender. No wireframe edges

Did you accidentally enable the clipping border?

AltB to clear it


How to make object visible only inside another object?

You can make parts of objects invisible using multiple tricks. Since your mesh is animated, it's probably not the easiest animating your material as well. As I get it, if you want to change the animation speed, you need to adjust the material separately. Anyways, here's how I would do it:

The sphere simply has a transparent shader set to blueish nothing else.
The cube is only visible if a ray has passed through a transparent shader. I guess you can also invert the sphere (animiation) and use a simple holdout shader on it, but I'm guessing that doesn't work for you for other reasons.


How do I get an object to ensure it is perfectly in line with the x, y and the z axes?

My guess is that you joined one of the legs as the final active selection. The final active selection becomes the new origin (and orientation) for the combined objects. The left middle leg looks like it's rotated 48 degrees on Y. Start again, select the body last. If you have accidentally moved it in the process, AltR, AltG will set it back in place.


Is it possible to limit the volume of fluid ejected from a mesh? 2.82

In the fluid simulation tab, the domain part, you should have Fluid Particles panel. Go there and set Generate to a more than zero value, like 0.5


I think this should help. when you are in edit mode, turn on this edge/face infos from the N key menu. this will show the scales of the parts you select.


Could this kind of texture be created procedurally?

Instead of using a musgrave node as in your .blend-file, I used two noise nodes where one of them controls the scale of the second one to make the fade "grainy". I also made the ColorRamp gradient a bit softer. See the node tree below:


I can‘t assign three materials and UV maps to multiple objects

The comment that moonboots gave is the best answer if all your cans are exactly the same. However, if the constraints and shape keys on them are differing from each other, those individual informations would be lost. So this might help as a workaround (if they still share the same mesh):

Select all cans so that the one with the correct UVs is the active one. Then Ctrl+L > Make Links > Transfer UV Maps. This way they have all the same UV maps.
Now you have to link all materials to the other cans. Ctrl+L > Make Links > Materials. Now all materials, no matter how many, are put on all the other cans.
The problem with this is, since you can copy materials to different objects that not necessarily share the same geometry, Blender doesn't transfer the information to which faces they are assigned. That's what you have to do manually.

It's still a lot of work I guess, but maybe less than having to do all constraints, shape keys, rotations, etc. over again. If someone knows how to copy face assignments for materials, please edit this answer.
A different solution would be: combine all three different materials in one material and separate them by masks and UVs, then all cans would only share one material with one UV map and there was no need for re-assigning faces.


If you are trying to Bake the Selected Object pass to the Active object without selecting at least another object, the operation fails: no information can be baked.

To bake a texure from a single object, you should disable the option by unchecking the box.

It comes out  grey because in BI the ambient occlusion get coloured by the Diffuse color (grey in your case).


How can I tell if a bone property has a keyframe on the current frame using python?

There is no easy way, but you could extend the Object type by a method:

import bpy

def is_keyframe(ob, frame, data_path, array_index=-1):
    if ob is not None and ob.animation_data is not None and ob.animation_data.action is not None:
        for fcu in ob.animation_data.action.fcurves:
            if fcu.data_path == data_path:
                if array_index == -1 or fcu.array_index == array_index:
                    return frame in (p.co.x for p in fcu.keyframe_points)
    return False

bpy.types.Object.is_keyframe = is_keyframe

# TEST
ob = bpy.context.object
pbone = bpy.context.active_pose_bone

# True or False
ob.is_keyframe(20, pbone.path_from_id("location"), array_index=2)

frame can be int or float, 20 will match a co.x of 20.0, but not a subframe like 20.1. If you want to check for full frames, use round(p.co.x) in the is_keyframe() function.

Talked to ideasman_42, and he may check on adding a native method to retrieve F-Curve and Keyframe objects more easily.


How would I create this material in Blender?

Yeah this is very simple. It's just a Diffuse and Glossy node put into a Mix Shader node. Turn the Fac on the Mix Shader towards the Diffuse side, and turn the Roughness on the Glossy shader down a bit.


How to view vertical zoom in Sequencer with Python?

This will zoom in on the y:

layout.operator_context = "EXEC_REGION_WIN"
zoom = layout.operator("view2d.zoom", text="Zoom Y")
zoom.deltay=1


How do I make steel in cycles using 2.5 as the IOR?

The FRESNEL node connected to a the FACTOR input of a MIX node which has for example a DIFFUSE and GLOSSY input will change the reflections depending on the angle that light strikes it.

The FRESNEL node has a panel for the IOR

http://www.chocofur.com/6-shadersamptextures.html


How Can I make the Camera follow an object but with a delay?

Slow parent needs to be enabled, and then set it to the amount of slowness you want the camera to lack behind. My English is terrible and I can't think of another way to word that.


Blender plugin import python from other file fail

importlib.reload only reloads modules, not arbitrary objects.

As BatFinger also suggested, import your module (so import operator_add), and not just one name from it (so not from operator_add import OBJECT_add). You can then reload it with importlib.reload(operator_add).


Details are directly connected to how dense geometry is.
Make the cube dense so that it has same amount of planes as your image has pixels.
So if your Planet lets say is 32x32px, the cube should have 32x32 planes to display it without additional artifacts.


Subdivide only showing in sculpt and render not in layout

in the first image post checkout the modifier multi res, there for the viewport its set to zero.
The idea here is that you can set different levels, ea while you work you can set it to low values, but when you render (or sculpt) you set it to high. so the memory load and speed of your pc is not harmed while working on your scene.


Blender Add-on Dev: Unregister is never called on Blender Exit?

The unregister() function is only called when you deactivate the add-on in your preferences, while register() is always called when Blender starts in case the add-on is activated in the preferences. You can test this with the following simple add-on that writes into a text file whenever one of the functions is executed. The example also includes how to add a handler that is triggered when Blender is exiting.

This add-on tries to write the test file into Blender's install directory. If that directory requires special permissions, then you should adjust the path to somewhere it can write the file to.

bl_info = {
    "name": "Register and unregister test",
    "author": "Robert Guetzkow",
    "version": (1, 0),
    "blender": (2, 80, 0),
    "location": "Dummy panel in View3D",
    "description": "Check when register and unregister are called",
    "warning": "",
    "wiki_url": "",
    "category": "3D View"}

import bpy
import atexit

class EXAMPLE_PT_panel(bpy.types.Panel):
    bl_label = "My own addon"
    bl_category = "Name of your tab"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"

    def draw(self, context):
        layout = self.layout
        layout.label(text="This is a label")

classes = (EXAMPLE_PT_panel,)

def exit_handler():
    with open("test.txt", "a") as myfile:
        myfile.write("exiting\n")

def register():
    for cls in classes:
        bpy.utils.register_class(cls)
    with open("test.txt", "a") as myfile:
        myfile.write("register\n")
    atexit.register(exit_handler)

def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
    with open("test.txt", "a") as myfile:
        myfile.write("unregister\n")

if __name__ == "__main__":
    register()


Have you removed doubles before you rigged the mesh?

Before ever rigging, you should always as a rule remove doubles in your mesh.
Anymore when you finished modelling, select your entire mesh, press hotkey W and select "Remove Doubles." That way, you will have leas tearing of topology and less disfigurements too.


Preview mode shows only a part of object

Your mesh seems to be severely corrupted and causing all manner of issues and unexpected behavior, including rendering artifacts and badly computed center for rotating view in Edit Mode.

To clean it up select you object, enter Edit Mode, make sure you are in Vertex Selection mode, and switch to Wireframe shading mode.

Select all vertex with Border Select operator (do not use the A  Select All operator) then hit P to separate it into a new object.

If you switch back to Object Mode you should now have to objects, a new one containing the actual geometry, and a second one with what appears to be loose edges.

Erase the loose edges and and it should fix your issue.


Using Blender to map XYZ objects from Homeworld RTS Space map HELP

Some possible manipulations or information :

Misc possibilities using Shift+S in the 3D view :

Short cuts :

Shift+C : brings back the 3D cursor to the center and places the view so that you see all objects
Home : shifts the view in order to see all objects
Alt+Home : idem but make so the 3D cursor is at the center of the view
NumPadDot : focus on the selection (one or several objects)
Alt+NumPadDot : set your current view center as pivot point (Alt+'.' again to come back to normal mode)

Outliner view, to search for something and select it :

So for instance, the outline allows you to find and select one of your object, then in the 3D view, you can hit NumPadDot to zoom on it.

Surely I miss here many other possibilities.. but hope that helps.

Edit :

Setting the units can also help :


nevermind, it was just me being dumb ... the button is there, i just needed to scroll up


Project light through shape, text or symbol to appear in cloud or mist

You could either model your batman logo or get one from the internet in SVG file format and use it as an actual "geometry stencil" in your scene to block out light coming from a projector line.
If you prefer you may also use an image texture as alpha map for your stencil

Just make sure your spot light is strong enough to make a visible influence and the size of the lamp is small enough so the shadows don't become too blurry, otherwise it may be difficult to make out the symbol

EDIT

For the materials simply use a Volume Scatter shader connected to the Volume socket of the Material Output. For the red volume use a very low density like 0.1 or less, for the blue volume receiving the symbol a higher density is acceptable like 1.0.

For a more physically accurate version mix a Volume Scatter and a Volume Absorption nodes using the Mix Shader node


After adding a new constraint,the whole rig is broken

change the pole angle in the IK constraint to have it pointing toward the pole target, you have to eyeball it.

Quadripedal Rigging: Twisted limbs

https://vimeo.com/171279647

The reason why the person in the tutorial didnt need to do it was probably because their bones had a different role angle (select bone in edit mode Ctrl R and rotate it) or the bones have a different rotation mode (select bone in pose mode, go to properties editor->bone->transform->rotation mode)


Bone constraint rotation not working correctly

I may be wrong but I'm not sure about this method, I think it works on the video because his foot is almost aligned to his controller on every axis, that's a solution by the way, but if they are not aligned, it will be ok as long as you rotate the controller on the X axis (because both bones are aligned on this axis), but, as soon as you rotate the controller on its Y axis or Z axis, the foot will go crazy (because you ask it to rotate on its own Y and Z and that's what it gives).

In my opinion the solution is to parent the foot to the controller.This way, the foot follows the controller no matter what. Then, if you want to make sure that the foot bone will stick to the shin bone, you can give it a Copy Location with Space > Pose Space and a Head/Tail value of 1.


The easiest, low-poly fire I can think of is the same setup done for trees and plants in many video games: Setup a plane textured with a fire image PNG (with transparency) and create duplicates that you rotate on the Z-axis.

This tutorial can serve as a starting point: https://www.youtube.com/watch?v=6dsP7N3l7kY

A different style with the same principle: https://www.youtube.com/watch?v=hkc-0YUz-Y4

Here is another quick an easy one that can be combined with ones above: https://www.youtube.com/watch?v=OYxb8F5moUo

This last one is about making solid-looking low poly trees, rocks and grass: https://www.youtube.com/watch?v=rtO9maU709k

Finally, it doesn't hurt to lean about particles, they can be simple or complex, realistic or stylized and can even enhance the low-poly ones with sparks. https://www.youtube.com/watch?v=jLjwN_JqUGU


Looping animation of an FXB imported character

I am importing characters from Mixamo.  In order to get both the skin and key frames imported into Blender only the following procedure works.

When exporting from Mixamo make sure you select from the "Key Frame Reduction" either uniform or non-uniform.  The "Skin" setting defaults to with skin

I'm still using Blender version 2.79b so I don't know how this will work in v 2.8.
I could only get it to work with the Blender Render engine.  Cycles engine imported neither the key frames which can be edited in the graph editor nor the skin.  So since Blender Render will not be available in 2.8, I would like to know if anyone has successfully imported characters from Mixamo with the skin and key frames?

But even in Blender Render once I change to another object and then change back the key frames are lost in the graph editor. Is there a way to display them again?


Point density halo particle system not rendering 'head on'

The rendering issues seemed to be tied to how massive the scale of the project was (Needlessly, too).
Scaling down to 1:10 (The object is now 100m long, not 1km) seems to have fixed the issues with rendering particles at all angles.


This answer should allow you to blur the texture (including Alpha). However, for this technique to work you need to use considerably more render samples to smooth out the noise, so blurring the images themselves (in the compositor or using an external tool such as Gimp or ImageMagick) would be a more efficient solution.


Texture painting applies color backwards

This sounds like inverted normals. You can use Ctrl + N to recalculate normals and then you can select the direction in the Tools panel.


How to map musical data to objects in blender amd export 3D printable .stl file

Assuming you have already baked a sound file to curve, you could evalutate the f-curves values and assign them to a prepared object e.g. massivley loop-cut cube.

import bpy

obj = bpy.context.scene.objects["Cube"]
action = obj.animation_data.action

fcurves = action.fcurves
for f in fcurves:
    print(f.data_path)

coords = []
for vert in obj.data.vertices:
    if vert.co.z > 0:
        coords.append( vert.co )
        print( vert.co )

ysorted = sorted(coords, key=lambda element: (element[1] ))

cidx=0
for i in range(200,250):
    curve_val = f.evaluate(i)
    ysorted[cidx].z = curve_val
    cidx = cidx + 1
    ysorted[cidx].z = curve_val
    cidx = cidx + 1

The vertices are first filtered by positive z-coordinste and sorted by y-coordinate so that opposite (on x-axis) vertices follow in a sequence. After that the curve value is evaluated and assigned to the z component of the vertex.

The resulting mesh is manifold and can be exported to.STL format.


Is it possible to render a movie on a single computer in blender?

It is possible to render a movie on a single computer. It depends on what movie it is. If you choose a style that renders extremely fast, it is possible. Nothing like the ones Disney make though. Not even remotely close.

Let's say you are rendering a movie that is 1 hour and 30 minutes. Let's say 1 frame of that movie renders extremely fast - 2 minutes. You are rendering 90 minutes of video, that is 5400 seconds and you probably need 30 frames for each second so that's 162000 frames. Each takes 2 minutes, so that comes to 324000 minutes that is 5400 hours and that is 225 days. So if you run your computer for 225 days, you will render your movie.

Now try having a simple scene that is inside some room and needs light that comes from a window(so it needs light that bounces around) and render it in 4k resolution in 2 minutes... That is a very hard thing to do. Chances are you will need a few hours at least for a single frame of any of the Disney movies on a single PC. That's why it is impossible to render on a single PC.


Particle and Fluid Forces driven by motion vector image data (XYZ vectors). Optical Flow

hmm just brainstorming.  Convert motion vectors to points use those points (make sure to keep points to a limited number) to act as effectors in a fluid sim. So you have to probably write a script that converts pixel location x,y,z data into points.  There is software out there but that's the extent of my knowledge on this.

I use this with the depth data from structure scanner to make a per frame point cloud.  It might work with standard motion vectors. Its a start.

https://github.com/arthare/stac_sample_decoder


Constant interpolation with Noise Modifier

I believe you can achieve what you desire by using an additional modifier after the noise - a Stepped modifier.

The Noise modifier generates the 'smooth' noise while the Stepped modifier breaks the curve into distinct bands (Step Size) and keeps the value at the same value for the duration of that band.


Subdivisions option in the Display rollout controls how the grid subdivides while zooming in the preset orthographic view:

  Subdivisions
   Controls the number of sub-lines that appear in each cell of the grid. In aligned orthographic views the level of subdivision depends on the zoom.

To stop the grid from subdividing at all set amount of subdivisions to 1. You might want to adjust Scale option to make the grid less big:

Note that this won't work in any other unit system except for the None which is by default, because both Metric and Imperial already have predefined spacing between grid cells so they aren't adjustable.


How do you transform a mesh with rig into another?

I would create one armature and one mesh, and use shape keys to turn this mesh from one shape to the other. Of course, the Dr. Banner version of the mesh may need to be rather dense, so that when it grows into the Hulk, it still looks detailed and smooth. For that reason, you may find that your system doesn't perform well when animating, and so you might need a low-res Banner mesh AND a high res Banner mesh for turning into the Hulk, with the high res version keyframed invisible/unrenderable, and all the modifiers for it deactivated, until it is needed. Both versions of the mesh would be bound to the same rig. I don't recommend trying to create two rigs. If you need the rig itself to get larger also, as I imagine in this case you would, I would keyframe the scale of the armature as a whole in Object Mode to coincide with the shape key animation change. I don't believe this will break anything, but I've never done it before. So if anyone knows of any pitfalls to this, please weigh in.


How do I make edges on a curve have equal length while maintaining the rough shape of the curve?

To subdivide the long faces on the length of your tube you can add loop cuts. Press ⎈ CtrlR and use the scroll wheel or ⇞ Page up to increase the number of cuts being made.

If you want to subdivide the top of your tube you could use the knife tool K to mark out the path of the cuts you want to make.

Another option for the top is to use the inset tool I to add loops parallel to your profile.


How to remove inner faces generated by union boolean modifier?

there is new boolean algorithm in blender, so use the exact option in the boolean modifier if you are in b3d 2.91 to remove that overlapping geometry, but in 2.83-2.9 or older you have to remove those faces manually after applying the modifier...


So I did some digging on this topic and found the answer. As future reference for 2D animators coming into Blender like me, stroke order for interpolation is the same as stroke order for stacking purposes. I do not believe there is a guide for stroke order because it was designed under a different concept - to be able to restack strokes like one would with layers. Stroke order is designed to be able to reorganize a layer, not aid in interpolation.
While this could be a bit of a setback, it also means that you are able to pick and choose which strokes are interpolated into others via the stacking order. Bringing a stroke to the front or back of a drawing will automatically sync it with the strokes on other frames.


How can I animate the visibility of a face?

You could use a Mask modifier if you really want to delete certain faces on a certain frame, however I'm not sure this is really what you want to do.
Mask modifier:
If you really want to delete a specific face (or faces) on a certain frame, then you can use the Mask modifier.

Select the faces you want to hide and assign them to a vertex group in Properties > Object data > Vertex groups

Add a mask modifier and select your vertex group and enable Invert by clicking the button next to the vertex group selector:

Keyframe the visibility of the modifier by hovering over the eye icon and pressing I.

If you want more variation, try using a reversed Build modifier. This will delete all faces in the object over time, either randomly or in order.
Fracturing:
If you are trying to make a more complex/realistic
You might also want to try the Cell fracture addon (see this post):

Or the explode modifier.


What tool do I use to make a part smooth

It's the subsurf mod! https://docs.blender.org/manual/en/latest/modeling/modifiers/generate/subdivision_surface.html
Extra characters to fill answer quota.


How Do I Shrink/Fatten Selected Along The X Axis?

Press the corresponding button on the keyboard to tell Blender which axis you want to use, namely: X,Y or Z. Select the faces you want to scale, press S and press X to scale along the X axis.


Why is glass material increasing noise, and what to do about it?

Short version: glass shader is more complicated and needs more calculations to obtain a nice result. So either you set samples to higher values, either you use some trickeries in the shader or in the rendering settings in order to reduce the complexity (but at the cost of accuracy).

I invite you to read the Blender Manual about Glass BSDF, which explains this more precisely as well as giving you ways to reduce noise.


What controls are there in the built in player?

A - toggle frame skipping.

P toggle ping-pong.

↵ Enter start playback (when paused).

Numpad 0 toggle looping.

Numpad . manual frame stepping.

← step back one frame.

→ step forward one frame.

↓ step back 10 frames.

↑ step forward 10 frames.

⇧ Shift+↓ use backward playback.

⇧ Shift+↑ use forward playback.

⇧ Shift hold to show frame numbers.

LMB scrub in time.

Ctrl++ zoom in

Ctrl+- zoom out

F flip image on the Y axis

Shift+F flip image on the X axis

I show frame indicator

Esc quit

Playback speed

1 NumPad 60 fps
2 NumPad 50 fps
3 NumPad 30 fps
4 NumPad 25 fps
⇧ Shift+4 NumPad 24 fps
5 NumPad 20 fps
6 NumPad 15 fps
7 NumPad 12 fps
8 NumPad 10 fps
9 NumPad 6 fps
/ NumPad 5 fps
- slow down playback.
+ speed up playback.

See also the Blender manual.


Sunroof style motion - conceptual issues

Add a follow path constraint and have the object follow a curve (yes both objects have to have their origins on the same place).

By controlling the offset you can make the object travel along the curve.

To control rotation use an empty as the control object for a copy rotation constraint.


Transition effect (common material to grid material)

Yes, compositing, you will have to assign the object to his own render layer, in order to treat it separately.


In the render settings, try to change View Transform from Filmic to Standard:


Why won't the location of the light affect the direction of the shadows?

Your lighting source is probably set to "Sun".  The sun lamp is meant to emulate a distant light source and therefore, placement is not critical.  In fact, you could place it anywhere and it would have the same effect.  The only things that produce an observable change are the rotation, the intensity/color, and the size.

There are other types of lamps (point, spot) that would work for this scene and you could always try a mesh emission source.  All of these are detailed on this forum.

EDIT: In response to your answer and comment: it is the answer to why your lighting doesn't change no matter where you place the lamp.  The answer is because you have it set to Sun.  I said that rotation is one of the only things you can change about the sun.  Position does nothing.

The reason you're not seeing the lamps is because you aren't choosing the right intensity.  The lamp themselves work perfectly:


AO Bake has random black pixels on some faces

The problem was caused by other objects overlapping the object that I wanted to bake.  When modelling I used the boolean modifier with some other objects and hid the old objects after applying it.  By deleting the old objects the bake worked perfectly.

Thanks to Leon Cheung and MarcClintDion for their help!


Export rigid body location without baking to keyframes

Yes, Location/Rotation/etc. returns the values visible in relevant fields of the object transform in the UI, kind of 'initial' transformation. To get final one, you can use:

bpy.context.scene.frame_set(250)
bpy.data.objects['Object'].matrix_world.translation

Note that:

This gives you absolute position of the object (world space), if you want its relative position (to parent e.g., local space), you'll have to use matrix_local.
You should bake physics simulation before using frame_set().


making a color ramp cycle back and forth

Sounds like you want a sine wave! Just multiply your incoming value by sin (with a multiplication node and sine node, respectively) and you'll get your oscillation of 0 to 1 and back again. There's some official documentation on just that use case here: https://docs.blender.org/manual/en/dev/compositing/types/converter/math.html#using-sine-function-to-pulsate

Then, add one 1, and divide the result by 2. This is a much smoother way of interpolating between 0 and 1 while avoiding negatives, as Rich Sedman suggested!

In other words, this set-up should go between your existing "Divide" and "ColorRamp" nodes:


How to generate a cylinder with several holes except by knife tool and Boolean methods

Create two inner circles
Extrude and scale a border around the inner circles
Bridge the inner circles together with two segments.  Note the number of edges in the perimeter of the resulting mesh.
Create an outer circle with a larger radius.  Use the same number vertices as the perimeter in step 3.  Extrude and scale a border.
Bridge the outer and inner circles together.
Extrude the whole mesh in Z-axis to create a cylinder.
Add supporting edge loops around hard edges.
Apply subdivision surface modifier and you're done.


There's lots of ways to connect a hole. The only rule you have to obey is that at least one edge has to connect the inner edgeloop with the outer edgeloop. Two or more are usually better.

If your mesh doesn't have to be watertight, and polycount is important to you, then you can even make a very simple hole as long as it gets covered by the other geometry (lower left).


Only 25 million faces and lots of particles in 6k resolution... why would you be running out of memory?

As pointed out in the comments you have no RAM left in your system.

Working in 3D is very easy to create situations where your scene is much greater than the resources on your computer.

You really need to reassess where you need to optimize. The trick is to think of where it is that you need great detail and where you can get away with less. The art of 3D is part precision but is mostly optimization.

For example, textures that are going to be just a few pixels on the screen can be rougher than those that are going to be featured in close-up.
Do you need that many particles or would a surface with a bump map would give you the same?

Not every strand of grass in the distance has to be a particle, The ones you don't see don't have to exist, the statues don't have to be as detailed if they are going to be so small, etc.

When Rendering on GPU you have even less resources than when you render on CPU, so it is unlikely that you will be able to use it to render such an ambitious projecet.

You need to slice the project in different layers that your computer can handle and composite later.

Here's a link that details how to do this: https://www.blenderguru.com/articles/how-to-render-a-complex-scene-without-crashing


The 3ds Max script must be using a copy of the data, if the data sent to the renderer is editable, but still independant of the scene.

There are a couple of other workaround I can think of.

Make a copy of the scene. Then use your python script on the copy and render it. You can delete the copy on render_post or just overwrite the scene everytime you start rendering. This will need a little bit more RAM, but no graphical memory if executed in background mode.
The above solution can be improved by making a linked copy (LINK_OBJECTS). It will not take up much more memory, since the data blocks the same. Then (on the copy) make the datablocks you want to change single users and change them.
Build an operator with UNDO activated and register it. Then, in your python script, call the operator (which does the changes), render the scene, then undo it. Depending on your scene, this may not be faster than a full copy, but will consume less RAM (I think).
Execute your python script from another empty Blender file. Append the scene (which you want to render). Make the changes, and render it, then delete it. Repeat. This is similiar to your setup, but could use the same background blender instance.
The above solution can be improved, by only removing and then appending objects which are changed by the python script.


By default, blender saves renders to a temporary folder, and deletes them after you close blender. It sounds like that's what happened. In the future, you should select a permanent folder to save the render to. This can be done here:

Unfortunately, there is no way that I know of that you can recover the lost render. However, if you select a render path, it should never happen again.


How does the "Depth" property work in image objects?

Default : Displays like any regular 3d object, if another object obstructs it, it will not display. If it obstructs another object, the other object does not display.
Front : Always displays in front of other objects, even if the view is obstructed.
Back : It will always display behind other objects, even if they are placed in front of them.

Note that this kind of image objects are meant for reference only while modeling and setting the scene, they will not be visible in the rendered image. If you need the image to render then import it using "import images as planes" or use the compositor to set a background for the scene.


how to render volume as image with alpha background?

The problem is due to the limitation of the image viewer (and the same problem occurs if you try and save your render as PNG) and is the same as that described in Rendering fire animations with transparent background. Change the viewer mode into RGB mode and you should see the results.

When rendering such an image (with combined alpha and emission) you should use a format that supports such images - such as EXR.


How can I check which of my collections are hidden in viewport?

Looping collections through bpy.data.collections gives you classes of type Collection:
https://docs.blender.org/api/current/bpy.types.Collection.html#bpy.types.Collection
Looping collections through bpy.context.view_layer.layer_collection.children gives you classes of type LayerCollection:
https://docs.blender.org/api/current/bpy.types.LayerCollection.html#bpy.types.LayerCollection
The meaning of the property hide_viewport seems to be slightly different in these two class types.

In type Collection it means: "Globally disable in viewports"
In type LayerCollection it means: "Temporarily hide in viewport"
Type LayerCollection additionally exposes the property is_visible, which is True, when the collection is both enabled and visible

I guess LayerCollection.hide_viewport is what you were looking for.
Code example to see the differences in action:
print('Looping type "Collection", property "hide_viewport":')
for collection in bpy.data.collections:
    print(collection.name, ' - Disabled in Viewport:', collection.hide_viewport)

print('Looping type "LayerCollection", property "hide_viewport":')
for layer_collection in bpy.context.view_layer.layer_collection.children:
    print(layer_collection.name, ' - Hidden in Viewport: ', layer_collection.hide_viewport)

print('Looping type "LayerCollection", property "is_visible":')
for layer_collection in bpy.context.view_layer.layer_collection.children:
    print(layer_collection.name, ' - Enabled and visible: ', layer_collection.is_visible)


The issue was fixed when I combined all feather meshes into one mesh.


You can use the booltron addon for this. It works with Curve and Text objects, but it isn't a modifier, it is a command. You select objects for a boolean operation (you can select more than 2) and press the operation name (intersect / difference / union).

Also, booltron fills holes before intersections.

This is the magic (I added a shortcut for the difference operation):


How do I connect vertices with a curve, then subdivide into more vertices that exactly match that curve?

You can apply a subdivision modifier to your mesh (You can also do that with a curve).

It will keep the same curvature.

You can also convert you mesh into a curve, change it the way you want, apply some subdivisions, and then reconvert that into a mesh.

Edit: You can increase the smooth value of the subdivision (on the left side, where you can set the number of subdivisions) or you can use the vertex smooth option in EditMode (on the same panel as before).

A.C


How to illustrate ideal refraction using cycles?

LuxRender shows refraction correctly.

Install LuxRender (currently support 2.82 and 2.83)
Setup a model with a refraction shader just like for Cycles
Render!

Sample Blend file -


I would use Object only if you have a good understanding of the applied scale of your mesh, and agree with the comment that for ease you can use Generated.

I believe that Modulo does not really help here (for your understanding's sake), as you are trying to segment the 0 TO 1 mapping that you are trying to achieve (You need to know how this works first).

When you take your Geometry, and get a mesh specific 0 (Lowest) & 1 (Highest), you want to keep that map, not destroy it with Modulo (Yet).

So for my first example I want to show you what that means to change it to an Add calculation instead, so you see what happens from 0 To 1.

Next You want to be sure when you introduce your Texture mapping node, that it connects to the vector inputs of all that would be affected by the rotation.

Now if you want to scale in a repeating striped way you could do this, and have the best of both worlds:

Just play with the B/W color ramp & the Brick Texture scale factor for preference, Or re-introduce your Modulo as you see fit (Now that you understand how the Texture Mapping is working).


BGE: Cube parented to another cube not colliding with objects

When you parent an object to another you implicitly declare the child to be a static object regardless if you set the physics type to dynamic.

If you look at the behavior you say: "I do not want this object to be controlled by the physics. I want it to follow the parent."

Therefore the physics will ignore this object.

From you question I guess you assume that the parent object considers the child. But why should it? If you want to "extend" the object you need to enable Physics/Collision Bounds/Compound on both the parent and the child.

If you need the parenting in-game see EjayACER's response. It describes how to do that with the parent actuator.


How to non-destructively solidify only certain faces?

There are really two ways of handling this issue.

1) As Denis suggested in the comments, check Only Rim. This won't give you thickness, but will just displace the faces in the vertex group.

2) Offset the Factor a small amount:


Yes it can.
Enter the blender user preferencesCtrl-Alt-U Add go into the themes tab.
In side the themes tab you can customize all the colors.

When You are done, be sure to hit Save User Settings.

You can also Down Load Themes:

You can download themes for site such as blendswap, or by searching on the internet.
To install a theme, press install theme, and then open your theme, which should be a .xml file.

Then save your settings.


Render yellow colored object as blue (design oriented question)

When using colored light, you have to remember that it affects the color of objects.  If you use a blue light in real life, most colors will not appear correctly.  If you look at the color chart on this page:

http://www.d.umn.edu/~mharvey/handbook5607.html

...you can see that under blue light, red, green, and yellow pigments will appear black.  Orange pigment appears dark brown.  Others just appear blue or darker blue.  It's just the science of light.

Here's a scene in Blender with pure white light:

The same scene with blue light:

and green:

and red:

If you must use a blue light, I'd make your dunes white or a shade of gray instead of yellowish-orange.

However, most scenes aren't lit with a single light source.  What you could do is add a touch of "moonlight" by adding a second light.  Here I made the blue light a "hemi" light, and then added a "sun" light that is light gray:

It's still blue and dark, but you can see the different colors again.


Shadesmooth visible in solid view but not in rendered view

Technical Details

The problem is not with the normals nor with the smooth shading. It is the result of the algorithm in the ray tracing engine used to determine lighting. Set the size of the sun to zero, and you will see one sharp line between the lit and dark area. Basically, the calculated normals would suggest that the surfaces should be lit, however geometrically the surface is facing away from the light, so the lighting will not be caluclated.

Possible Solution

Generally such biases are always present for smooth shaded meshes, simply because the surface is only approximated with polygons. The better the approximation, the less these glitches appear.

In you case, the problem is, that there are 90 degrees sharp edges shaded smooth. Those are not really realistic either. You could make them sharp either via Properties Panel / Mesh / Normals / Auto Smooth or by adding an Edge Split modifer.

Here is the issue isolated and the Edge Split added:


Modify default settings for subdivision surface modifier

The video you linked to is a tutorial for the Sensei addon, which is a free addon that you can download and try. You will notice that the Sensei addon replaces a lot of the blender UI so that it's own operators are used, which is how the various defaults are different than blender's defaults.

Like the Sensei addon, you can create your own addon/s that perform tasks with your settings. You can start by creating an addon that defines an operator which adds a subsurf modifier with settings you want as well as turning on the draw wire settings for the object. This can be then be added to existing menus or custom hotkeys. To learn to create addons start with a Python tutorial if you don't know Python yet, then go through blender's addon tutorial.

Some code to put into your operators execute() method could be something like -

# bpy.context.active_object is needed if you test this script
# inside an operators execute you only want context.active_object
obj = bpy.context.active_object
# objects draw wireframe settings
obj.show_wire = True
obj.show_all_edges = True
# add a subsurf modifier
m = obj.modifiers.new('Subsurf', 'SUBSURF')
# this turns on optimal display
m.show_only_control_edges = True
# this shows the edit mode vertices on the
# deformed mesh not the real vertices
m.show_in_editmode = True
m.show_on_cage = True


Animation changes after applying mirror modifier

The object has an origin which is used as center for the rotation but your object is made by doubling mirror on object so the initial object's origin is being used as the generated object's origin by the animation.

To fix this you must separate the mesh obtained after applying mirrors into 4 meshes, into edit mode select the faces of one propeller, press "P" and hit "selection", you must do this three times so that you have your four propellers.

Once this is done you still have one thing to do, it is to set your 4 objects origins: use "Shit-S" to access the alignment tools and use it in edit mode to set your cursor precisely where you want your rotation axis to be.

Then back to object mode "object>tranform>origin to 3d cursor", you could also use origin to geometry (in this case blender will interpolate between all the vertices of your object and set its origin there) and note that geometry to origin is the same as "apply location


How to make a Delete operator with its confirmation window?

Invoke the WindowManager.invoke_confirm
IMO the way this was is confusing. If your desire is to delete an object by name, can instead get it from the scene by name and remove it.
As it was would remove active, selected and "obj" if it existed, or simply throw an error if it didn't.
Have passed an override to the delete object operator to only delete the object known with name self.obj if it is linked to the context scene.
Test script, run in text editor throws up the confirm menu.
import bpy

class MYADDON_OT_Delete(bpy.types.Operator):
    bl_idname = "myaddon.delete"
    bl_label = "Delete Object"
    bl_options = {'REGISTER', 'UNDO'}

    obj: bpy.props.StringProperty()
    use_global: bpy.props.BoolProperty(default=False)

    @classmethod
    def description(self, context, event):
        return f"Delete {event.obj}"

    def execute(self, context):
        scene = context.scene
        obj = scene.objects.get(self.obj)
        if obj:
            return bpy.ops.object.delete(
                {
                     "object" : None,
                     "selected_objects" : [obj]
                 },
                 use_global = self.use_global
            )

        return {'CANCELLED'}

    def invoke(self, context, event):
        self.use_global = event.shift
        wm = context.window_manager
        if event.shift:
            return wm.invoke_confirm(self, event)
        return self.execute(context)

def draw(self, context):
    layout = self.layout
    op = layout.operator("myaddon.delete")
    op.obj = "Cube"

if __name__ == "__main__":
    bpy.utils.register_class(MYADDON_OT_Delete)
    bpy.types.TEXT_HT_footer.prepend(draw)
    bpy.ops.myaddon.delete('INVOKE_DEFAULT', obj="Cube")


These are backup files created by Blender and are fairly normal.

Excerpt from the wiki

  Save and Auto Save

  ...To reduce the chance of
  losing files when those events occur, Blender can use an Autosave
  function. The File tab of the User Preferences window allows you to
  configure the two ways that Blender provides for you to regress to a
  previous version of your work...


Blender 3D UVs scale issue appearing after export _FBX_OBJ_COLLADA

Zak!
Thank you, yes I did that after the boolean operation.

Actually, I found the thing... I opened the programs individually and I saw the process of UV generating in the early beginning - by the default cube. It looks like there is the KEY for my issue.

In each of the programs by default UV layers were generated for the 1st cube in a different configuration. I saw that in 3D's max, and Cinema4D they are equal to reset textures in Blender operation, stretched to the whole UV for each individual face.

Thank you! Anywhay!


While I'm not certain what process you went through that resulted in your edges being split wierdly, you should be able to fix all wierd verts on the model by selecting all, pressing Alt+M and selecting "By Distance". This merges vertices that are X distance from other vertices.


How can i view white wire in sculpt mode?

Two things to do.

For the wireframe color, go to User Preferences > Themes > 3D View > Active Object colour.
In the "N" (shortcut) panel turn on Backface Culling under Shading tab to hide back part of your mesh.


How do I bring back the little menu under the main window?

Near the upper and right corner of the red box in your 2nd image there is a small + click it and the small section will restore ;).


Is it possible to keep particles orientation relative to the emitter when the emitter is rotated?

You have to check Rotation, to make the particle system uses the dupli object's rotation. Using this setting, particle orientation can be tweaked by rotating the dupli object itself:

Next, give one of the object's local axis as the particle system's initial rotation. This way, any new particle will be oriented to that axis:

Now any new emitted particle will always be correctly oriented:


How to clean up almost-symmetrical vertices?

'Snap to Symmetry' under Mesh in Edit mode should do it.

https://docs.blender.org/manual/de/dev/modeling/meshes/editing/basics/symmetry.html

'Symmetrize' on the same menu may also help, but note that it is quite destructive.


my smoke simulation doesn't render correctly in cycles

The solution is empty space in smoke domain settings. it should be zero.


The Driver System

Can use the driver system for this.  An fcurve is a series of frame, value points. The value of an fcurve at any frame can be found via FCurve.evaluate(frame) A scripted expression driver evaluates its expression at each frame.  context.scene.current_frame is already known to the driver namespace as frame, as are a considerable number of math methods and properties including sin, cos and pi

Type simple expressions directly into the property preceded by a hash "#".

Will show as purple if all is Ok.  Can edit at any time by clicking on the driver.


Easy way to run python script in blender python console?

In Blender 2.80 and higher, you can use as_module().

In the above example, an unsaved text editor shows this code:

def myTestFunc():
    print('This is my test function, running')

print('This is my test module, running')

Then, in the Blender Python console on the left, you can import this:

myModule = bpy.data.texts[0].as_module()

Note that since this is my only text file, I've used texts[0] to reference it.  If you had multiple, you would reference by name, such as texts["Text"] or similar.

Note that anytime the source code changes, you will have to re-run the as_module() command again to pick up the changes.

Finally, I can call functions from the module I imported, like so:

myModule.myTestFunc()

This uses the variable name that was assigned by the as_module() line, and looks for a named function within that module to call.


Glossy object is almost invisible when rendered

When dealing with glossy objects, like mirrors, you have to think that instead of lighting the object, you need to take care of whatever is being reflected on it.

So create something interesting that can be reflected on your mirror-like object and make it stand out from the backdrop:


How to select only visible vertices using python API?

First of all, as for the select_all behavior, that is by design.
Calling bpy.ops.object.select_all(action='SELECT') is the same thing as pressing the A key, which selects ALL items, even ones outside of the view frustum, even ones occluded and not visible.
To select visible vertices in python similar to border or circle select honoring bpy.types.SpaceView3D.use_occlude_geometry and bpy.ops.mesh.select_mode:
import bpy

def getView3dAreaAndRegion(context):
  for area in context.screen.areas:
      if area.type == "VIEW_3D":
        for region in area.regions:
          if region.type == "WINDOW":
            return area, region

def select_border(context, view3dAreaAndRegion=None, extend=True):
  if not view3dAreaAndRegion:
    view3dAreaAndRegion = getView3dAreaAndRegion(context)
  view3dArea, view3dRegion = view3dAreaAndRegion
  override = context.copy()
  override['area'] = view3dArea
  override['region'] = view3dRegion
  bpy.ops.view3d.select_border(override,
                               gesture_mode=3,
                               xmin=0,
                               xmax=view3dArea.width,
                               ymin=0,
                               ymax=view3dArea.height,
                               extend=extend)
  return view3dAreaAndRegion

Then to use this, just add after the function definitions:
select_border(bpy.context)

Blender >2.8
def getView3dAreaAndRegion(context):
  for area in context.screen.areas:
      if area.type == "VIEW_3D":
        for region in area.regions:
          if region.type == "WINDOW":
            print("Found WINDOW")
            return area, region

def select_border(context, view3dAreaAndRegion=None, extend=True):
  if not view3dAreaAndRegion:
    view3dAreaAndRegion = getView3dAreaAndRegion(context)
    print(view3dAreaAndRegion)
  view3dArea, view3dRegion = view3dAreaAndRegion
  override = context.copy()
  override['area'] = view3dArea
  override['region'] = view3dRegion
  bpy.ops.view3d.select_box(override,xmin=0,xmax=view3dArea.width,ymin=0,ymax=view3dArea.height,mode='ADD')

and then, with a selected object in Edit mode, run
select_border(bpy.context)

Very important: This code needs to be run in a window that has a 3D Editor view in it. So if you're running the code editor in a separate detached window, it won't work !


Can I make edits made in edit mode appear in animations?

Yes, there is a way, called shape keys.

Other question, where shape keys are explained: How to animate a mesh that changes through editing?

Select an original pose and do the first shpe key, then do your facial expression, or whatever, in editmode and add another shape key. One Shape key by, eg facial expression. By changing an expressions value, the expression whichs vallue you make the highest dominates. Shape keys can be animated by holding the mouse over the value and pressing "i", setting a keyframe.


Okay this is a fairly simple solution then, I'm going to point you there instead of answer it yet, because I'm on my phone and not in front of blender (I will have to circle back around on this).

You need to get into the animation_data of your objects. This has driver, expression, and variable properties within. The big tip here is that you need to create a new variable before the expression will actually work. To get at these it's going to be something like:

bpy.data.objects["Cube"].animation_data

Here is a quick append to this answer for now to help you understand the data structure. However before you copy and apply this data to another object there is more to prepare on the "OTHER" object.

Still planning on circling back around on this to finalize this lacking part of the answer.

c1 = bpy.data.objects["C1"]
# This is the reference to my Original Cube with the Driver

dr1 = c1.animation_data.drivers
# This is the Driver collection of my Original Cube

dr1[0].data_path
# This returns 'scale'

dr1[0].expression
# This simply returns my expression 'var', because I am using a 1:1 mapping of another object's scale factor

dr1[0].driver.variables[0].name
# This returns the first (and only in this case) variable that I have named in this driver 'var'

dr1[0].driver.variables.items()[0][1].targets.items()[0][1].transform_type
# Returns 'SCALE_X'

dr1[0].driver.variables.items()[0][1].targets.items()[0][1].transform_space
# Returns 'WORLD_SPACE'

Without being able to confirm this yet, I'm going to recommend that you explore the following approach to get the copy:

For the sake of my code above, please follow my case (ultimately it should follow suit in yours).

I'm going to reference a second Cube whose name is "C2".

CONFIRMED

So for the prep on this object, before you can copy the data try:

c2 = bpy.data.object["C2"]

#If you were to create it manually -> c2.driver_add('scale', 0)
#Since you are copying do something like:

dr2_path = dr1[0].data_path
dr2_index = dr1[0].array_index
c2.driver_add(dr2_path, dr2_index)

#Now get reference to your new driver & Create a new Variable
dr2 = c2.animation_data.drivers
dr2[0].driver.variables.new()
#by default this should be 'var' if this is the 1st.
#You should now be able to copy the expression, target, etc... over from c1

dr2[0].driver.variables.items()[0][1].type = dr1[0].driver.variables.items()[0][1].type
dr2[0].driver.variables.items()[0][1].targets.items()[0][1].id = dr1[0].driver.variables.items()[0][1].targets.items()[0][1].id
dr2[0].driver.variables.items()[0][1].targets.items()[0][1].data_path = dr1[0].driver.variables.items()[0][1].targets.items()[0][1].data_path
dr2[0].driver.variables.items()[0][1].targets.items()[0][1].transform_type = dr1[0].driver.variables.items()[0][1].targets.items()[0][1].transform_type
dr2[0].driver.variables.items()[0][1].targets.items()[0][1].transform_space = dr1[0].driver.variables.items()[0][1].targets.items()[0][1].transform_space

Here's the proof of the rest of this code in play:


How to move the master bone of a rig to the actual pose?

You never move the rig in object mode, you want to use the Root/Master bone exactly for this and also you never move the rig away from the Root/Master.

The reason is when you only animate bones, you get only 1 Action. Whereas when you animate also the object you get 2 Actions and it's messy. Can be problem when the rig is linked and you need to apply animations to the proxy. You also can't save such pose to pose library. Etc. this can go on and on why not to do it.

There is no easy way of fixing it. You will have to investigate what bones are parented to the Root/Master, move those bones back and position everything with the Root. And if you have animation do it for every keyframe.

If you have lots of keyframes it might be better to bake the animation. You do this by creating and parenting an empty to each bone that is parented to Root(local axis should correspond). You then bake animation to the empties. Then you move (and animate) the Root where you want it and override the transforms of parented bones with Copy transforms constraints from the empties. Then you bake the animation to the bones and you delete the empties.


Probably this file has been accidentally overwritten:

You can delete it and copy an original file from another PC.


Is there a way to insert keyframes for a group of frames using python?

zeffii's answer is better than using bpy.ops, but if you want to get closer to the metal, it gets a little clumsy.  Blender's action API is missing several convenience functions.

It boils down to these steps

make sure the datablock has animation_data
get the animation_data.action or .action=bpy.data.actions.new(name)
find the action_data.fcurves[i] that matches the data_path and array_index, or create the fcurve
make sure there are enough fcurve.keyframe_points to load our data into
assign the fcurve.keyframe_points[j].co and possibly .interpolation, .handle_left, .handle_right, etc.

There are a couple of examples embedded in http://web.purplefrog.com/~thoth/blender/python-cookbook/movie-card-stack.html and http://web.purplefrog.com/~thoth/blender/python-cookbook/csv-to-fcurve.html which I will summarize here:

def make_or_get_fcurve(obj, data_path, index=-1):
    """
    :param obj: the data block from which we'll get the fcurve
    :param data_path:
    :param index:
    :return:
    """

    # freshly created objects don't have animation_data yet.
    if obj.animation_data is None:
        obj.animation_data_create()
    ad=obj.animation_data
    if ad.action is None:
        ad.action = bpy.data.actions.new(obj.name+"Action")

    for fc in ad.action.fcurves:
        if (fc.data_path != data_path):
            continue
        if index<0 or index==fc.array_index:
            return fc
    # the action didn't have the fcurve we needed, yet
    return ad.action.fcurves.new(data_path, index)

and from the other example

def find_or_create_fcurve(action, data_path, array_index= -1):
    for fc in action.fcurves:
        if fc.data_path == data_path and ( array_index<0 or fc.array_index==array_index):
            return fc
    fc = action.fcurves.new(data_path, array_index)
    return fc

def make_eyeball_look_at(armature, frame):

    eyeball = get_eyeball()

    cns = find_constraint_track_to(eyeball, armature, "card release")
    data_path = 'constraints["%s"].influence' % cns.name
    fc = find_or_create_fcurve(eyeball.animation_data.action, data_path)

    i0 = len(fc.keyframe_points)
    fc.keyframe_points.add(4)
    kp0 = fc.keyframe_points[i0]
    kp1 = fc.keyframe_points[i0 + 1]
    kp2 = fc.keyframe_points[i0 + 2]
    kp3 = fc.keyframe_points[i0 + 3]

    kp0.handle_left = [frame - 7, 0]
    kp0.co = [frame - 6, 0]
    kp0.handle_right = [frame - 5, 0]

    kp1.handle_left = [frame - 4, 1]
    kp1.co = [frame - 3, 1]
    kp1.handle_right = [frame - 2, 1]

    kp2.handle_left = [frame + 2, 1]
    kp2.co = [frame + 3, 1]
    kp2.handle_right = [frame + 4, 1]

    kp3.handle_left = [frame + 5, 0]
    kp3.co = [frame + 6, 0]
    kp3.handle_right = [frame + 7, 0]

def add_keyframe_points(fcurve, kps):
    idx0 = len(fcurve.keyframe_points)
    fcurve.keyframe_points.add(len(kps))
    rval = []
    for i in range(len(kps)):
        kp = fcurve.keyframe_points[idx0 + i]
        kp.co = kps[i]
        rval.append(kp)
    return rval


Cycle Combined bake only adds lighting on side of mesh

Found the reason, it was that since it was an empty scene it could only bake unto itself. The surface at the top was facing nothing, whilst the surface on the sides could reflect off of eachother.

That means if you want to have a light source also show up in a picture, that light source needs to be inside of some sort of object, such as a sphere or whatnot.


How do I open up a window I have closed in blender?

In the top left of any viewport window you'll find this button:

You can turn any window into any other type of window from here, and completely customize your workspace.

In your case, you were in the 3d viewport, but you were in either rendered mode or material preview, and now you're in solid mode.  You can switch between these by pressing Z while your mouse cursor is inside the viewport, or using these buttons in the top right.

Last, if you don't know what you just closed, you can create a new workspace of the type you were working in, here.

You can delete the old workspace and move on like nothing happened.


Go to File > User Preferences > Addons and search for Add Curve: Extra Objects and activate this addon
In the 3D view add a new curve object from the Spiral type. Adjust its settings as desired.
Add a new curve circle with a radius similar to the sphere.
Now to the spiral curve apply an Array modifier fit to a curve using the circle as length definition.
Next add a curve modifier to it using again the circle as deformation curve.

You can now freely adjust the bezier curve circle as desired to match desired length and radius. Set it's handles to Free and then subdivide it to make shorter segments.

EDIT
The trick here is using a bezier circle as deformation in the Curve modifier, since it will guarantee a perfect fit around the sphere as long as the body is truly spherical. You can then rotate both objects at the same time (curve circle and spring-like spiral) at will and it should always fit around the curve.


Create a cylinder with all normals pointing to the inside

To flip the normals of your cylinder, Tab into Edit Mode and key T to toggle open/close the Toolshelf. Go to the Toolshelf > Shading/UVs tab > Shading dropdown > Normals section and click Recalculate. This will align all the normals. Now, you can click Flip Direction to align the normals on the inside of the cylinder.
Note that as lemon said in the comments, Ctrl + N is the shortcut for Recalculate, and Shift + Ctrl + N is the shortcut for aligning the normals to the inside of (an object), not flipping them, aligning them to the inside of an object.

To check your work, first, make sure the exterior and interior shading has been flipped. Next, key N to toggle open/close the 3D Viewport Properties panel and go to the Mesh Display tab. I like to turn on Face Normals. Now, every normal will appear as a little blue line in the center of each face.


Compositing with render layers that are unchecked

It could be more efficient not to animate the renderability of the Render Layer rather than to animate amount of samples for that Render Layer instead.

Find and animate Samples option which will override scene setting for samples.

This amount of samples can be set up for each Render Layer separately. So when that layer should be empty, drop the samples amount to some small value (but not to 0 as it will mean default which is the scene values) and the perfomance will be increased.

The layers still will be overlayed; you can bypass data from one of them animating the Factor of the Alpha Over (or Mix) node (e.g. setting it to 1 to make only bottom layer visible).


It looks like the face outlined in blue is part of a separate object from the one you're editing.  Toggle out of edit mode and select the other object, and edit or delete that.


With version 2.78, you can now draw curves onto surfaces.

To use it:

Add a Path curve in object mode (Shift + A >> Curve >> Path).
Enter into edit mode (TAB).
T to show the Tools panel.
Under the Options tab set your Projection Depth to Surface.
Under the Create tab click Draw Curve or alternatively Shift + A >> Draw Curve.

NOTE: you can play with the Tolerance under the Options tab to get settings to your liking. After creating your desired curve, delete the verts that make up the original path.

Create a thread mesh design.
Add an Array modifier to your thread mesh, setting its Fit Type to the curve object.
Add a Curve modifier to the thread mesh, setting its Object to the same curve object in the Array modifier.

For me, I picked the start point of my curve as being the origin of the curve, and set its position to the origin of the thread mesh, then played with the Constant Offset of the Array modifier.

Here's was my results:


All you have to do is increase the number of frames that your animation takes. Go to the dope sheet and select "action editor" now select all of your keyframes with A and press S and then press 2. This would slow down your animation by half.
Edit: I will add images to show you

As you can see, now the animation takes up double the amount of frames. Meaning it will take twice s long to complete, meaning it will be half as fast.


Python: Copied Object Not Showing in Outliner

Link it to a collection
Prior to 2.8 a copied object required linking to the scene's objects collection.  For 2.8+ link it to a collection.
It will show in the outliner when collection is linked to a scene, or is the base scene collection.
The duplicate operator links the dupe to the context collection.
import bpy
from bpy import context

ob = context.object.copy()
context.collection.objects.link(ob)

link new object to scene with python in 2.8


Blender rigged horse - foot gets stuck to the ground when moving the animal

The mesh is wrongly skinned to the Armature. Vertices of the bottom parts of the legs are probably influenced by root bone. To avoid that you should turn off Deform on the root bone (you should also turn it off on the IK target bones), clear bone groups, that was created by Parenting with automatic weights,delete Armature modifier and clear parent from the mesh. Then repeat parenting with automatic weights and you'll be good to go. Below you'll find image with the placement of Deform option in bone properties.


Rotate an Ico sphere with 20 sides(Icosahedron) to align with the level grid

Create your Icosphere
Add a new Empty object
Turn on Face Snapping
Turn on the Align Rotation with Snapping Target option
Move the Empty object and press Ctrl while transforming to snap
Make it align to one of the desired faces
Afterwards select the Icosphere, then Shift-Select the Empty (so it stays the active object)
Press Ctrl+P to parent the Icosphere to the Empty
You can now move the empty freely wherever you want, and most importantly clear its rotation from the Toolshelf or with Alt+R
When correclty aligned unparent the Icosphere, and optionally apply its rotation if desired with Ctrl+A > Apply > Rotation


I've had a chance to look at the actual blend file, and I found geometry problems.  Let me show you how I found and fixed one.
I took your Cube cutter into edit mode in a local window.  (If you have a number pad on your keyboard the / character on the pad toggles that mode.)
Then I used the select menu to select interior faces

Turns out you've got one:

That's going to confuse the boolean operator, so delete it.  Use the X key and select "Faces".
It still doesn't work because you have two objects you need to apply the Boolean to, "Blade" and "Middle Knifu"; so I added the boolean to each.

and it worked.
ASIDE: You have a lot of bad geometry in both the blade and Middle Knifu.  In addition to interior faces you have duplicated vertices and you have interior edges.
ORIGINAL ANSWER STARTS HERE:
Be sure that you apply the Boolean modifier to the cube that represents the blade and not the object you are using to 'cut' the hole.  Here's a crude example:

What you don't see in the example is the cylinder I used as the 'cutter' object.  If you look at my scene collection you'll see why:

When you select the blade and go to the modifiers panel, the Boolean modifier should look like this:

Notice that the modifier is applied to the blade and that the "Object" in the modifier is the cylinder.
Below the Object there's a 'Solver' box.  I have it set to Fast.
A common rookie mistake is to apply the modifer but leave the cylinder visible.  If you do this it looks like nothing happened:

There are a couple of ways to solve this.  For the example I simply made the Cylinder invisible:

If you do it this way, the cylinder will still show up in renders.  You have to also make it invisible to the camera:

Alternatively, if you are going to use a lot of Booleans a better technique is to move the cylinder to a new collection, usually called 'cutters':
Select the cylinder and type M.  this will bring up a menu:

Since you don't already have a collection, select "new collection" and give the collection a name.

Now all you have to do is uncheck the box for the cutters and the cylinder won't show up in the 3D view or on a render:


Viewport render uses the image size settings of the current renderer.

Change the resolution here:

And render using:


You may need to change from Ortographic to Perspective using Numpad 5 and try zooming in again.

Look in the top left of the Viewport: if it says Ortho you won't be able to see the "inside" of objects, if it saysPersp you probably will.


Join all the objects you want to unite using Ctrl+J
Create a new cube that contains all the joined objects inside
Use the Boolean Modifier on the Cube with Carve Solver and Intersect Operation


Here is what I achieved using transparent nodes and AnimAll addon.

Create a plane and give it a 'slashy' shape. Add a curve and place a mesh along it using a Curve Modifier. Add a Subsurf Modifier also if you like.

Prepare two textures- a color map texture (in this case I used a hair photo) and a mask texture (a simple oblong b&w gradient image).

Create two UV Maps- first for a color texture and second for a mask (which will be helpful in achieving the fading effect). Unwrap the mesh using Project from View (Bounds). Scale the island of the second UV map as shown below.

Set up the nodes as pictured below. We want to use the color texture for the emission color and as a mask for a transparency. Optional you may add an extra overall transparency to the mesh (just add one more transparency node and mix it with existing nodes).

Now we'll set up an oblong gradient texture as a mask for a fading effect.

Place the uv island as pictured below, enable the AnimAll Addon and check the UVs box . Go to the desired start frame and insert a keyframe. Next, place the uv island in the dark part of a gradient texture. Go to another chosen frame and insert a keyframe again. Play the animation in Object Mode and you'll see the fading effect.

Here is the same animation as on top, but with less transparency and played slower.

Here's the .blend file:


Use tracking information from video to make a 2d panorama

The only way to achieve this in Blender I think is with Dynamic Paint. But the vertex paint can be poor quality. You'll have to bake an image sequence. Of course you only need the last frame.

Track the image with 1 marker. Use "offset" if marker leaves frame.

Solve the track for Tripod.
In Geometry tab of the MCE link an empty to the track.
Go to the 3D view and create a plane for the canvas, subdivide it
lots. The more you subdivide it the sharper the image later.
Give it a Copy location Constraint (new empty)and a copy rotation
constraint (camera rotation).
Press 0 to look through the camera and scale the canvas so that it
covers the camera view from first frame to last.
Then add another plane using the Images as Planes addon. This will
be the brush.
Give it a constraint to copy the camera location but in edit mode,
scale it to fill the field of view and move it towards the canvas
object.
Add a Solidify modifier so that the image plane goes through the
canvas plane.

Go to the physics tab and activate Dynamic paint > brush. Set
 material to the movie image material.
Now select the canvas and in the physics tab activate the Dynamic
 paint > canvas. Turn down Drying time to 1 frame.

The canvas should move below the camera in sync with the original camera move. The source movie should be projected onto the canvas from the camera point of view.

To reduce the processing you would use fewer frames from the source pan. Blender won't drop frames in Texture mode so you would have to preprocess them in the VSE, by applying a speed effect which will drop frames. In this way a pan that could use 100 frames could be created with just 10 frames. Tracking would be a bit more challenging.


How can I Toggle "Autolocking of Layers" without accessing "Layer Specials" Menu (Blender 2.92.0)?

While I was just about to post this question, a possible answer dawned on me. If you right-click the "Autolock Inactive Layers" option from the "Layer Specials" menu, you can add the function to Quick Favorites. I completely forgot about that option! This is great for getting me through at the moment. But I'd still like to know if there is another solution.


It is common to add loop cuts to a model. It is also common to keep loop cuts to a minimum.

A bit of planning can help prevent loop cuts getting too excessive. In your example you have loop cuts to define edges of parts of your window shutters, these don't need to continue all the way around the house. The window shutter could be an object that is separate from the house with loops cuts that only exist in the shutter. Even if you keep everything contained in one mesh, you can have disconnected mesh parts that contain loop cuts that are local to each part.


Why is the default cube pink when the material is set to white?

Never mind. I had an HDRI set up and it got moved. That was the missing texture.


Rendering an animation the way 3D view looks

You can render using OpenGL, by going to Info > Header > Render > OpenGL Render Image:

Or by clicking on the icons in 3D view > Header:


Model Deforms after applied the Mirror modifier

It looks like you have the x mirror option enabled in the options tab of the toolbar. My guess would also be that to have the option behave that way your rotation should be applied as well, but just disabling the x mirror should fix it.


Is it possible to add holes on volumetric clouds in eevee 2.92?

This is not volumetric and this is not exactly the same effect (I'll edit if I find something closer to what you show) but you could do something like that:

I've created a bezier circle and a cylinder, given the cylinder an Array modifier (with Fit Type > Fit Curve with the curve as Curve) + Curve modifier (with a bezier circle as Curve Object) + Subdivision modifier + Displace modifier (with a Cloud texture):

Then I've given 2 or more shapekeys to the cylinder, stretched it so that it deforms, and keyframed the shapekeys:


Does the compositor affect image quality?

No, the compositor will not degrade rendered images.
The compositor works with 32bit float precision, in scene referred linear (meaning that there is way more information that what can be displayed in the monitor).
Of course, there could be intentional or unintentional degrading in the compositor caused by incorrectly connected nodes and/or poor judgement by the user.
A likely source of image degradation is the use of highly compressed images in lossy compression schemes (like jpeg or mpeg), in which the the original image will suffer corruption with each subsequent cycle of decompression and re-compression.
As for Color Banding, it would happen when the image is saved to 8 bit formats, as this method of encoding cannot resolve subtle color gradation with only 255 levels for each color. Areas of similar colors, and dark, almost monochromatic gradients, will suffer greatly.
To disguise banding in the rendered image, use dithering.
Note that even if the image is saved as 16 bit or 32 bit per channel, it is possible that it cannot be displayed at a better quality: Most monitors display only 8 bits per channel (and some even less than that). Banding then is inevitable (just pause any of your favorite movies during streaming and you will see what I'm talking about). Banding might disappear if the higher bit depth images are displayed properly in a 10 bit monitor or better (retina display or any professional grade monitor or video projector)


Cannot deform mesh with automatic weights during rigify process. Tried all solutions

Your model has lots of issues:

select the mesh in object mode
in the modifier stack remove the armature modifier;
R Z 90 (rotate the model by 90 degrees around the Z axes);
Ctrl A Apply rotation and scale;
Select the MetaRig and M move it to a different layer.
In edit mode A select all and remove doubles 0.1 mm (I removed something like 30.000 doubles).
Back to object mode select the mesh, select the rig Ctrl P, choose the "With empty groups" option and go with manual weighting: paint weight or assign weights via the properties panel, vertex section, vertex groups tab.

The automatic weighting is a simple shortcut for simple meshes: they must be manifold, joined, without holes and seams; your mesh is maden of multiple spare parts and is far more complicated than what is manageable by the automatic algorithm.


How to model small details above curved surfaces?

If what you want to do allows it (several kinds of shoes in the question, but maybe this is ok for second and third pictures), you can obtain this very simply:

The model is a simple cube opened at its base, with a vertex group that is one for the bottom vertices and 0 for the top.

Modifiers:

Subdivision that will propagate smoothly the vertex group values and gives geometry for the shrinkwrap below
Shrinkwrap to project on the surface, using the vertex group
Bevel... to bevel and smooth the base

This is not a pure modeling, surely... but its quick and often invisible for small details.


How do I create only one of multiple new face outcomes?

It seems that there is no easy way to do this automatically in your case.
You can create faces between edges manually by selecting the edges where you want the face to be, and pressing F.

Create the inner faces: Select neighboring edges, and press F

Repeat this for other faces to make the inner cross:

To avoid creating non-quad geometry, we need to subdivide the outer ring to match the edge count of the inner ring. Select the outer edges (you can loop-select by using Alt+ Click), And subdivide them with 2 cuts:

Now we have the same number of edges inside as outside (3 for each side). You can continue this process, making faces where needed, to fill the remaining geometry.
You can also use the Bridge Edge Loops command to fill multiple faces at once.
Alternative Method
There is a much simpler way to create the window-like geometry you want:

Create plane
Subdivide for 2x2 grid
Set the Transform Pivot Point to "Individual origins"

Select all faces; Extrude Individual Faces; Esc to avoid offsetting

Scale (S) the 4 faces to make them smaller:

(This will scale them individually because of step 3)

Delete the unnecessary faces!


Material Preview
Material Preview uses one of the builtin generic HDRi maps to light the objects.
It is for preview purposes only and wont affect final scene lighting, nor will it be exported along with the model.
In this mode scene lights are ignored (optionally) for performance and workflow reasons. You can enable them in the Shading Popover.
Render Preview
Render preview uses your actual World Shader as background color instead and lighting.
Scene lights are also previewed closer to final result. They are still never exported to other applications though, so in external game engine or environments results will always differ.
You can switch the HDRi on/off for both preview modes.

Also see related How to use Default HDRIs in Renders?


How to animate a surface that only emits light when touched by object?

Set up your reactive surfaces as a Canvas for Dynamic Paint, and your contact surfaces as Brushes.

You can store the effects of the brush on the canvas either as vertex data or as a a UV-mapped image.

In this example, The steps were UV unwrapped, and a wetmap was baked as an image sequence, which was then used as the factor to mix between a diffuse and emissive shader in the steps' material. The wetmap was set to fade after about 40 frames. On the whole, the tools guide you through their use; I can't think of any major gotchas.

The Canvas (Steps) was set up like this:

The Brush like this:

I baked out the maps using the 'Bake Image Seqence' button in the 'Canvas' panel.

You can use the image sequence as a mask. something like this:

And this is the sort of result -

The method given here bakes the paint result to image-maps, on the assumption that you won't want a highly subdivided model in your architectural render. However, to preview the effects of the various settings, it would be better to make a highly subdivided test-bed canvas, (a plane will do) and set up a simple brush, say a sphere. Then set the 'Format' in the canvas to 'Vertex', and the mode to 'Paint'. Then by having the animation set to continuous looped playback in the timeline, and moving the brush with respect to the canvas, you can see the effects of settings live in the viewport.

I would suggest you want to select 'Wetmap' as the preview in the Output sub-panel, and play with 'Spread' and 'Shrink' effect speeds, and 'Drying' and 'Dissolve' times in the Advanced panel. Also adjust the initial 'Wetness' (load) of the brush. These will all interact to give a variety of organic feels to the animation.

Don't forget, either, that the wetmap can wind up being used to mask a variety of other effects in the material of your steps, including, for example, other textures, which may themselves be animated. The results can also be used to control particle systems.


After googeling hours and hours i found out, Blenders Collada exporter is just buggy. For everyone who wants to use Blender and Assimp together i recommend the FBX file format. Both, Blender and Assimp do support it, you can configure Blenders FBX exporter to use the correct Coordinate-System (-z forwards, y upwards) and it even supports exporting all animations on the animation-stack as individual animations.


Using the node editor in a private project

While it isn't documented much, blender does support custom node trees. You can start with the custom nodetree template in blenders text editor. You may also find some help searching here for pynode.

Two example projects using custom node trees are animation nodes and sverchok.

As you are defining each nodes functionality, you don't have to access or modify blenders data, so you could use blenders node editor while making each node read/write data to files.


Use Edge Split

Do not use hard shading, always use smooth shading on the whole object and use the edge split modifier instead. You can split edges based on angle or mark edges sharp with ctrl + e and mark sharp manually. This will make blender report the proper vertex count when no seams are present. Using the script that counts the UV vertices should give the proper vertex count with edge split and seams.


You should use proxy when working with video editor.


How can I make my own mesh and add it to Addmenu > Mesh?

You'd have to create your own add-on for this. First create a Python function that creates the mesh, then create an operator to call that Python function, then add the operator to a menu. There are loads of online tutorials on how to do these things; the Blender API documentation is a good start, as it also includes information about best practices and common pitfalls.

You can check out the built-in Add Extra Objects add-on to look at similar functionality.


CLI How to render last frame of hair dynamics sym?

Bake the Pointcache

Here is a test script that bakes the first particle system on context object to first point cache.

import bpy
context = bpy.context

ob = context.object
# assume we have a particle system
ps = ob.particle_systems[0]
pc = ps.point_cache

# match bake to animation
print(pc.frame_start, pc.frame_end)

bpy.ops.ptcache.bake({"point_cache": pc}, bake=True)

Have a look at the PointCache members in the API, and will see that among others it has

pc.is_baking
pc.is_baked

Now to test this in bg mode.

Confirmation

Can confirm that, with script above named test.py the command blender2.8 is an alias to my blender version 2.8

blender2.8 -b test.blend -P test.py -f 250

when run on blend that is no more than  default cube, with default hair particle system, (with dynamics) produces following output

Read blend: /home/batfinger/blender/test/test.blend
1 250
bake: frame 1 :: 250
bake: frame 2 :: 250
bake: frame 3 :: 250
bake: frame 4 :: 250
...

bake: frame 248 :: 250
bake: frame 249 :: 250
bake: frame 250 :: 250
Fra:250 Mem:182.13M (0.00M, Peak 183.09M) | Time:00:00.33 | Syncing Cube
Fra:250 Mem:182.17M (0.00M, Peak 183.09M) | Time:00:00.38 | Syncing Lamp
Fra:250 Mem:182.17M (0.00M, Peak 183.09M) | Time:00:00.38 | Syncing Camera
Fra:250 Mem:182.18M (0.00M, Peak 183.09M) | Time:00:00.41 | Rendering 1 / 64 samples
Fra:250 Mem:182.17M (0.00M, Peak 183.09M) | Time:00:00.77 | Rendering 26 / 64 samples
Fra:250 Mem:182.17M (0.00M, Peak 183.09M) | Time:00:00.97 | Rendering 51 / 64 samples
Fra:250 Mem:182.17M (0.00M, Peak 183.09M) | Time:00:01.07 | Rendering 64 / 64 samples
Fra:250 Mem:124.26M (0.00M, Peak 183.09M) | Time:00:01.30 | Sce: Scene Ve:0 Fa:0 La:0
Saved: '/tmp/0250.png'
 Time: 00:02.24 (Saving: 00:00.94)

/tmp/0250.png