Faces become distorted, strange and look glitchy when looking through camera view

It looks like Z-fighting, probably the clip distances is set to a very large number.

The clip range should encompass your scene, not the whole universe. A large clip range will result in lower depth precision, creating Z-fighting, where the render engine cannot determine which surface is in front or which one is behind. In other words blender cannot tell apart faces that are parallel but in close proximity with each other.

For more info read these links:

Shadows along edges of mesh in 3D View

Weird Tears in terrain mesh in Render View only

Weird shading effects when rendering at long distance


Problem with getting a clear and smooth glass surface

A couple of changes to default settings
The Principled BSDF shader has a default Base Color around .8, which means glass will be a little dark by default.  You can raise the base color to 1.0 for perfectly clear glass.
These dark spots -

are caused when the light reflects internally a number of times that exceeds the number of bounces allowed in render settings.

Usually it's the number of Glossy bounces which you can change here:

You can learn more listening to this talk.
To the model
When modeling for subdivision it is often to your advantage to leave your mesh as low poly as possible, and let the interpolation algorithm do the work of placing the additional vertices with mathematical precision.  Shade Smooth will do the rest by interpolating the normals between the generated faces.
Observe the following model, and see how it is represented in edit mode.

(5 levels subdivision)

The glass tubes might be easier to construct using a curve.  This takes a lot of the work out of positioning.  I added a solidify modifier to this curve.

As a bonus, the curve may serve as a constraint for animation.


The number of frames the simulation plays for is dictated by the domain cache:


How to assign vertex color to vertex color shader node?

face.material.new(name = 'Skin')

'face' has no material property. And as the material is new, there is no vertex color in its node tree (and no node tree as it is).

You can:

mat = bpy.data.materials.new(name = "Skin")
mat.use_nodes = True #Make so it has a node tree

#Add the vertex color node
vc = mat.node_tree.nodes.new('ShaderNodeVertexColor')
#Assign its layer
vc.layer_name = "skin"

Now to link the vertex color output to the default principled shader:

#Get the shader
bsdf = mat.node_tree.nodes["Principled BSDF"]
#Link the vertex color to the shader
mat.node_tree.links.new( vc.outputs[0], bsdf.inputs[0] )

Additionnaly, if you want to add it to the 'face' object:

face.data.materials.append(mat)


Wrap text around a Circle without deforming it. (numbers on clock)

On the surface, and for most text the Text On Curve option would work great. The clockface however is the one example where the positions of the Numerals are more important than the perfect spacing between them.

See here in green the marks where the midpoint of these Numerals would need to be to make the clock look as expected, but automated Justify  or setting the Spacing of the Word will result in an indiscriminate offset (shown by the red markers).

You can tweak the individual spaces between consecutive characters, even between a space character and a letter. This is called Kerning and it can be positive or negative. The keyboard command is Alt + Left / Right.

The technique is as follows: You place the text in edit mode while it is on the Curve, then navigate with left / right to the spaces between the Numerals, then to increase spacing you do Alt+Right, and decrease space Alt+Left.

In the End it may look something like this. (which I still think looks wonky)

Consider using a background image to help decide where on the perimeter to place these numerals. It's not trivial to get comfortable spacing (but you can copy from the masters).

Problems with this method

I still have issues with this because the Curve is also applied between individual characters of the Numeral. You may or may not have an issue with that, but many clocks don't use that kind of Text On Curve aligning.

What I would do.

I'd do it with Sverchok (full disclosure, I coded some of Sverchok and wrote the Typography / Type Draw node):

For the Sverchok file here's a .blend of that node setup.

or

Add a Circle of the desired size. (with 12 vertices)
Add One Text Object
Give the Text Object the Center Align
Make the Circle the parent of the Text Object
Set Duplication in the Circle to Vertices and tick the Rotation box

You might get something like this:

with the Parent object (Circle) selected, press ctrl + shift + A to make the Duplicates Real.

Still with the Parent Object (Circle) selected press U to get the Make Single User menu , choose Objects & Data from this list. Now you can edit the Numerals individually :)


Can I add "min" and "max" properties to the "location" property?

After looking at the documentation, I do not think there is a built-in option for an object's location (some other Blender values may be, but you could check on Blender's API docs).  It would be best to use a FloatProperty or FloatVectorProperty.  You could use a setter so it updates the object's location whenever the value changes, but that would also require some way to keep track of the object for the property.


It sounds to me like you're looking for the Hook modifier.


Subsurf, triangulate and UV texture problem

Blender doesn't subsurf n-gons or triangles that well. Try retopologizing the mesh, and then applyong the subsurf and triangulate modifiers and UV them after that (you can duplicate the mesh before you apply the modifiers so you have a backup)


Child object doesn't move with parent bone

I'm not sure if the same applies to the game engine, but when animating the bones don't move the body unless they share the same name as the (vertex group) they are meant to move.

this link shows how to make vertex groups
http://www.youtube.com/watch?v=w1EZZIsiIUA

I assume you already have bones, go into edit mode and make sure each one has a name which matches its appropriate vertex group.

sorry if this doesn't help.


How do I make a round cornered rectangular box with a domed top - for 3D printing

A quick, destructive approach:

Starting in the flat, a plane subdivided along the convex dimension
O proportional editing, spherical profile,  G Z raise the central edge / face.
Subdivide in the other direction
E Z extrude the perimeter edges downward, and  S Z0 flatten them
Ctrl B with  a few segments, bevel the sharp edges.
Maybe scale some edge loops inwards, to ease the curvature in the vicinity of the bevel

Solidify and Subdivision Surface modifiers,  for thickness, and smoothed high-resolution, for printing.


The "Bloom Color" parameter is actually a filter. It determines to what extent emission colors create a Bloom Effect. If it is set to white, the emission colors will not get filtered and therefor every possible combination of RGB values will create the desired effect with the corresponding color. Basically, the color of the Bloom Effect is the product of "Bloom Color" and emission color.


How to export rigged character with ik or fk with .fbx format

You cannot. Supporting basic bone animation is already a total nightmare, so we are not even remotely close to start dreaming about supporting things like constraints or IK in FBX (not totally sure FBX does support IK, actually…).


How can I create a "volleyball sphere" for sculpting?

You can make such object as well.

Start with a default cube
Add a Subdivision Modifier
Add Cast Modifier, factor set to 1, to make it into a sphere


Select the light you have -> properties editor->enable shadows and enable contact shadows in it.
It is only necessary for cycles render engine


How to mix 2 keying nodes in the compositor to keep the alpha channel from both?

put one into the other as so - that way each node changes the previous


To increase the brightness, change the strength of the lamp to a higher value.

If you want more even light, I recommend changing your light to an area.


One way is to use multiple loocuts.

Set Pivot center to Individual Origins
Scale and move the secondary loopcuts
Use the Shear tool to adjust the rotation.


Do you have to download a special version of Blender to use experimental features?

No, you don't need a special version of Blender. They come with Blender. You can enable them in various places in Blender.

For example, the experimental rendering features:

Another example - add-ons:

For your specific case, enable the experimental rendering features like you mentioned, then switch displacement type in the material settings (this will work with something attached to the displacement input of the material output node).

For setting up displacement, you will likely want to use a subsurf modifier with the "adaptive" setting enabled.

Here is the example .blend:

Note: The viewport doesn't properly reload yet, so you have to keep switching between solid and rendered view.


Enabling OpenCL GPU rendering for Cycles on Linux?

To enable opencl on linux working with blender, the only way is to install the official amd-pro driver, or, as I did, only the opencl part.
Unfortunately, the only Linux distro officially supported are:
RHEL 8.0 / CentOS 8.0 and 7
Ubuntu 18.04.3 (and derivative) (so, all the kubuntu, xubuntu, lubuntu etc and mint)
SLED/SLES 15 SP1 (and opensuse leap)

So, with Debian You are in a bad spot, unless You play around quite a bit


scissor car lift animation rig objects not following path

Markom3D has recently done a small YouTube series on modelling and rigging a SciFi landing gear here. He explains how he modelled the pistons at 6 minutes in part 1 and how the model is rigged in the final part called 'How to rig a SciFi landing gear'.
Hope that is of some help.


How to arrange selected vertices in a perfect circle

I think the easiest method is to use the handy LoopTools addon which is already included in Blender. Just enable it in User Preferences -> Add-ons.


Letter Text One By One In Correct Location

Not intelligent but brutal approach: track furthest vertex (max X coordinate) from full length text and use it as location offset.
Text (solid shade) - object with single letter
Text.001 (orange wire) - full length text for tracking purpose

Unfortunately, execution will get slower on every next letter due to mesh converting and sorting.


How can I specify filenames of animation renders as [SCENE NAME] + [FRAME] when rendering an image sequence?

This answer already explains how to render certain frames.

bpy.context.scene.name             ...   the scene's name
bpy.context.scene.frame_start      ...   the scene's starting frame

import bpy

scene = bpy.context.scene
fp = scene.render.filepath # get existing output path

for frame_nr in range(scene.frame_start, scene.frame_end):

    # set current frame
    scene.frame_set(frame_nr)

    # set output path
    scene.render.filepath = "//render/" + scene.name + "_folder/" + scene.name + "_customName_" + '{0:03d}'.format(frame_nr)
    bpy.ops.render.render(write_still=True)
 scene.render.filepath = fp

Refer to:

padding ints with python
the range function


How can I make triangle using mapping nodes?

I'm "math disabled" ;) so this is my dumb version of triangle.

You can change Rotation in Mapping nodes as well as values in math nodes to achieve different triangles.

What it does is basically creating 3 black&white planes and then rotating them and offsetting.


Applied emission, set strength quite low but still looks really over exposed, any ideas on how to correct? Doing The CG Fast Track Beginner Tutorial

You've connected an emission shader directly to the volume output for the world.  With this connection you're saying "emit light from every point in the world" so it pretty much doesn't matter how low you set the light, it's going to be pervasive.
Here I've used a principled volume node and used the density slider to control the amount of fog in the scene, then I made the fog emit just a bit of light.

I encourage you to take liberties with tutorials, because not only did I learn a lot that way, but you'll find yourself creating pieces with a personal touch.


The command you are looking for is called SHEAR. Select the vertices you want to rotate and press Space and type in "shear" (or ShiftCtrlAltS at the same time)


Objects created by Blender see through on Unity

The reason you're seeing this effect is that in game engines like Unity, typically only one side of every face is rendered. Faces have a front and a back, and only the front of a face is rendered. This is typically done because in many circumstances, the back sides of faces are never seen, and it is much more efficient to never render them.
To better preview what your mesh is going to look like in Unity, you can turn on Backface Culling in Blender.

If you do need a face to be visible from both sides in Unity, you can duplicate that face in Blender, and flip the normals (the direction the face is pointing) by pressing ALT+N, then F.
Typically though, real life objects (like walls) aren't infinitely thin, so you will usually have a face defining either side of a wall, with some distance in between.


How can i merge one object smoothly into another while animating?

You may use shape keys to make such animation, but it demands joining the objects together.

Join the meshes with Ctrl+J. Connect the meshes' vertices in Edit Mode. Try to keep the topology clean. After making it one solid mesh add two additional edge loops (Ctrl+R) and place them as pictured below. These will be helpful for further creasing.

Go to Data header-->Shape Keys panel and add two shape keys being in Object Mode. Select the second one, press apply shapekeys in edit mode button and change its value to 1.000. Select the bottom of the character's neck in Edit Mode and press Shift+S-->Cursor to Selected (with a 3D cursor as a pivot point set). Use a border select tool (B) to select all the body vertices. Then press Ctrl+Num- to unselect the very top edge loop. Press S,0 to scale vertices. Slide the edge loops pictured above (press G twice) to crease the edge of a toilet. Your transformation animation is ready.

Now being in Object Mode apply the transformations to the object (Ctrl+A). Change the value of the shape key to 1.000 and keyframe it with I. Select the object and move it down (G,Z). Place it on the grid floor, then press I-->Location. Now go further on a timeline, press Alt+G to reset location, then keyframe the location again with I. Change the value of a shape key to 0.000 and keyframe it again.

Here's the .blend


Select sharp edges what's the angle value

You determine yourself the value on the bottom of the 3D view Tool panel (on the right of the 3D view, activated with T). Every edge with an angle above this one will be selected.


Problem after closing with bend modifier

Since you've created that band by bending a rectangular prism then removing doubles, I believe there's an extra face that you didn't delete, right in the center where the two ends had met (running along the cross-section of the band). You need to delete that inner face since the subdivide modifier is using that face to average out the vertices.


duplicating a surface and making it a child node

Duplicate, separate and parent

To get the surface you'll have to duplicate the faces.

Enable Edit Mode, select the faces you need, duplicate them by pressing shift+d.
Your new faces shall now be selected, but they still belong to the cube object.

To separate them press p while the faces are still selected. Choose "Separate" in the pop up menu to tell blender that you want to put those faces in a different object with "selection" criteria.

Now that you have two diffeent object you can parent with hierarchy.


How to easily identify which nodes have logic bricks attached to them in the outliner

You can run the following in the Text Editor to select all objects in the scene with a logicbrick.

import bpy

bpy.ops.object.select_all(action="DESELECT")
logicbricks = ("controllers", "sensors", "actuators")
for obj in bpy.context.scene.objects:
    if any(len(getattr(obj.game, brick_type)) for brick_type in logicbricks):
        obj.select = True
bpy.context.scene.objects.active = obj


Often times faces appear darker if their normals are flipped. In computer games these faces are usually not rendered. Blender however makes sure that they are and hints to the user that the normals are flipped. To test if it's a normal issue you should check enable backface culling in the 3D views properties panel

Your faces however seem pitch black thus this could imply a few things:

Faces are assigned to a material which is pitch black
Faces are mapped to a black/empty region in your texture
You're seeing the vertex colors assigned to the vertices.

edit:


How To Bevel A Single Edge To A Flat Surface?

So you could simply select this edge and bevel it?


You can enable the Snap > Vertex option:

Then select the top 2 vertices, move along the axis (here X), keep pressing Ctrl to snap and snap to the bottom vertex:


No Grease Pencil Option Showing (at all)

You are looking in the wrong place.

in 2.79 the controls for grease pencil are on the tools and properties window.


Futuristic water tower—seemingly simple shape, but how tackle a clean topology?

Use simple shapes and pump up the subsurf subdivision

I would suggest to model your object with simple shapes (e.g. cubes for the pillars, an octagon for the top) then add the subsurf modifier and start tweaking the geometry with the modifier activated.

Let the subsurf modifier do the work for you. Use the minimum amount of vertices in order to easily control the shape and let the smoothing flow.


Blender Render rendering dark, spotty and weird image

Looks like it's a problem with your world background.  Not sure if you had an HDR image in there but it wasn't packed in the blend file but I found what I believe to be the correct one from HDRHaven.

So you need to pay particular attention to the enviroment texture node.  This should be set to Mirror Ball projection with Raw color space.

Also you need to plug this into the background node, then the background into the World Output Nodes surface input.

I also suspect that your area lights have too much power, so dialling these back to results in the following rendered at 720P with a mild fog glow composite node:

Here's the updated blend file (be careful, I ramped up the Cycles resolution to a higher value, don't fry your CPU trying to render this)

Update

There was a problem with the mesh of the glasses (I'm sure I mentioned this last time). I've fixed it, shows a noticable difference.  I've also upped the lighting, but I think this is too saturated. I've updated the render and blend file.


How to spread/Scale Vertexes by world constant range?

Use "push/pull" to give a distance in world units:


Use the curves modifier

The curves modifier can be found in the video sequence editor.
Inverting the pixels is easy by changing the shape of the curve(s). The left point (representing the darkest pixels) originally at 0 should be set to 1 (to map those pixels to be the brightest) and vice versa the right curve point from 1 to 0.
Here is a gif:

This gif only shows the work for the C-channel (luminance) which is enough for inverting a B&W-video. Note that you have do the same for the R-, G- and B- channels if you also want to invert the colors.


Why is my dynamic paint image sequence coming out blank?

your subdivisions of your plane is far too big. So just make your plane much (!) smaller or subdivide it more (which i do not recommend if you do not want to crash your computer) - i just made your plane really tiny (after i rebought a new computer when i tried to subdivide it more...) and then  bake your images again and i got small red lines on the pngs. But i think your Shader setup is wrong too because i never saw red lines on the plane.


I solved, after two months from when the problem occurred. I used the irc chat and three or four forums and, of course, Google.
The page that helped me a lot is https://developer.blender.org/T28790
where it says that is a problem of ffmpeg with the compiling of GCC. You can solve that downloading the precompiled version here https://builder.blender.org/download/
It doesn't work if you compile the version and also the repository one does not work.

I answered my question to help all the people that will have the same problem =)


Blender always selects the shortest path when selecting vertices how do I turn this off?

By default, Blender's behavior will pick the shortest path (eg. everything between point "A" THRU "Z") if you hold the Ctrl key on your next selection.

If you use Shift instead, then it will just append the selected item to the set of items selected (eg. Just point "A" & "Z").


Making three vertices symmetric without moving middle vertex

You can use snap to symmetry feature.
Select vertexes that you want to move in mirrored position. Then in menu choose Mesh -> Snap to Symmetry.
Then you need to adjust threshold using Adjust last operation (F9 or panel in bottom right corner)
Optionally, you can edit factor, to define what vertexes you want to move.

Then you can use X-mirror option to keep this vertexes in sync. This setting is located in 3 places:


Making two different bones copy different axis on a target bone's rotation

I believe what you need is to copy rotation.
Under bone constraints, select copy rotation, and select the bone you want to take the rotation values from. You can also choose which axis to copy.

In your case, as you want the red bone to follow the hand bone's y axis, you would add a copy rotation on the red bone, and make the target the hand bone (green). Then you would uncheck the x and z boxes, so the red bone only looks at the hand bone's y rotation.
You would do the same with the blue bone. Add contraint, set target as hand bone, then make sure only z is selected.
If you are unsure of how to target the hand bone:

Under Target, select Armature
A new box will appear underneath, labelled Bone
In the Bone box, select the hand bone.

You can also use the eyedropper icon. Select it, on the right of the box, and click on your Armiture, in the 3D (main editor) view.


Trying to rig a character but the rig won't work

Parenting the rig to the character will not do anything except make your rig object follow your character object if moved arround.

If you want your character object to be deformed by your rig, you need to parent your character object to your rig with an armature deform.

To do this, select your model, then your armature, hit ⎈ CtrlP to open the Set Parent To menu, and any of the Armature Deform's three sub-options :

Once it's done, depending the option you chose, your rig might already be able to move your character, but it's very rough, parts might be poorly assigned to bones, ... So you will probably have to edit this yourself.

If you chose Empty Groups or automatic weights (which I recommend for new users), you will have to go in weight paint mode and tweak.

There are a lot of tutorials and manuals about this process, so I invite you to find a nice one for you and see how it goes.


Is there a method to create bl_info using variable?

No
Sure this is a dupe, have searched and searched,
For want of a better reference

https://developer.blender.org/T53617
bl_info must be declared in the module.
This is because bl_info is extracted without executing code.

ie the bl_info dictionary is grepped out of the addon module top level file (foo.py or foo/__init__.py) as a string where the  locals will not be available.


I solved the problem by copying addons from makehuman package and by not by downloading explicitly. Idealy both mush be same.


Subdivision surface modifier, faces not connecting

As moonboots suggested, the Edge Split modifier is the culprit here. It literally turns every edge into 2 edges creating disconnected faces which messes with subsurf.
Edge Split Modifier Doco
You can test this by turning "Sharp Edges" off and reducing the "Edge Angle" value down to 0. You will notice that every face becomes rounded as though every face is disconnected. (Cool effect though!)

For what you are trying to achieve, using Crease is a much better option.
Delete the Edge Split modifier, select the edges you wish the subsurf modifier not to effect and hit Shift-E to add a crease to those edges. It is a bit of an art knowing which edges to apply Crease to but you will learn it as you go. The crease value can also be found in the N-Panel under "Item"


Why does my model reorient itself when I render it?

You have inserted keyframes , the viewport is displaying frame 2922 and you are rendering frame 0.

you can change what frame you want to render in the render settings.

to clear all keyframes select all objects and press Alt+I


Selecting just the outer edges doesn't work in this case, this is how I would do it:

In Edit Mode use Face Select, select all the inner faces of those grooves.
Make sure you have set the Transform Pivot Point set to Individual Origins.
Hit S and then Z to scale them on the Z axis as far as you want the outer edges to be.
Then hit Ctrl+Numpad Minus to reduce the selection of the inner faces.
Scale them back again on the Z axis with S and Z.


In the Outliner, when you click on the object mesh icon, it allows you to enter in Edit mode and to edit the object mesh, it doesn't allow you to precisely select one part of the mesh if that's what you're trying. If you don't see anything when you click on this icon, maybe it's because your object is not visible on your 3D View, it can be on another layer for example. Also, when you try to edit an object, why don't you select it and press tab to enter in Edit mode? This is the classic method.

About your display problem: You must accidentally press Z, it makes you switch between Rendered (or Material) mode and Wireframe view. See what happens on the bottom horizontal bar of your 3D View.


Used boolean modifier for lettering on 3D print. It won't print letters, but shows as working

Try with file https://drive.google.com/file/d/0B7t43CPM6VA-RURVZDg0NGhuTEk/view?usp=sharing (I'll delete it from my drive at Oct 28).

I did the following:

Converted text to mesh.
Combined all text meshes together.
Extruded text meshes on Z axis.
Did the boolean modifier to carve the plate.
Applied the modifier to the plate.
Deleted the text meshes.
Exported to STL.


Every addon uses a register function that allows it to add operators, panels, extra properties etc that it uses to work, it also has an unregister function to undo these changes when the addon is disabled.

If disabling an addon gives errors after being disabled that are related to properties or functions that it setup, then it is a bug in the addon that should be fixed.

You may notice that the addon you refer to is from addons_contrib, which is a collection of addons available that haven't been accepted as official addons to be included in release versions. Chances are this error is a known one and is one of the reasons it is still in contrib. In this case a release candidate is not being considered as a release version and includes the contrib addons, which may not be the best option.

While reloading scripts can help in some cases, it doesn't remove every change and start from scratch, for that you will need to quit then start blender. I believe reloading scripts relies on the unregister functions mentioned earlier to work properly.

Whether you are using a new install or an old one, it depends on the addon scripts enabled to whether any issues like this happen.


How to retopologize low poly object with a few detailed points?

This is just my suggestion ;). With this kind of topology you'll be able to crease edges. And it's a bit less messy than yours.


Black pixels in render when using Cycles material

I am not getting those spots when I render the scene.  Perhaps try rendering with the CPU instead of the GPU.

I rendered with the CPU.  My results:


You can recalculate roll, (Armature -> Bone Roll -> Recalculate Roll), or Shift+N

This can align bone roll to local or global space.


use texture to control the size of the particles as follows :
 - add a texture to the particle system

in the texture tab change the influence to size

here is the result :

white regions -> full size particle
gray region -> small particles


First, join your 2 objects with CtrlJ.
Then you can use the LoopTools > Bridge. First thing, open the Preferences panel and activate the addon called LoopTools, then:

Bevel the inner edge loop, cut a hole:

Select the edges that you want to bridge, right click > LoopTools > Bridge:

Tweak the factors in the Operator box (Segments and Strength):


How can I make a perfect sweep with bevel object in Bezier curve(3d) (Pipe)

Short answer: No you cannot. It's a known limitation of the current system and unfortunately there is no current way around it.

This is currently planned to be improved as part of 2016 GSOC Bezier Curve Improvements, but if it will ever be successfuly done or actually land in an official Blender release remains to be seen.

Either use a 2D curve, which causes no distortions, add extra control points near the tight bends to minimize the deformed area or where possible use separate segments. See this answer for more details.

Alternatively if you want to use simple pipes with exclusively straight or angled segments and don't mind using mesh objects instead try using one of the builtin addons Pipe Joints

https://blender.stackexchange.com/a/53486/19307


Is there an option for ghosting in armature in blender 2.8?

I have found (but not yet tested) this Add-on for Blender 2.80 which claims to do onion skinning (a.k.a. ghosting) on any mesh objects: https://blendermarket.com/products/onion-skin-tools


Smoke Simulation - Bake Offset before Frame 0

I am answering myself, it is a workaround

set frame Start: -125 frame End: 125
click "Bake" the sim should bake, but not move in preview
"Free Bake" and go to frame 0
Let the smoke simulate in viewport from frame 0(do not click Bake)
Click "Current cache to bake"

Voilá


Unable to update/replace existing keyframe

So of course I find the answer a few minutes after I write up the question. I was selecting the entire armature, pressing I to insert keyframe and selecting "position". When I tried using "whole character" instead it worked as I'd hoped.


I am pretty sure Blender can do this. The physics is far better than most people think. But....you have to be careful.
I will show you the first step, the next steps you can do according to them.
I made it to animate physically the small golden gear with a motor.

Stabilize the gear with this cylinder (rigid body passive)

change small golden gear to rigid body active, shape mesh, margin 0
same to blue gear
plug the motor like this: add an empty like this: the x - direction is important, else the motor won't work

add rigid body constraint to empty like this:

increase the rigid body substeps:

if you start animation with spacebar, the blue gear will rotate, driven by the small golden gear

result here: https://www.youtube.com/watch?v=LsVekqC-Lno&feature=youtu.be
because of your comments...here next steps

copy the passive cylinder from step 1 to the green gear like this:

stabilize the gear by extruding the cylinder on the other side so that the gear won't fall off like this...please don't kill me because i just make it work, but not pretty, i know my modelling is ugly... ;(

set the green and the big golden gear active bodies with shape mesh and margin 0.

copy the empty from 1st motor to the green gear like this:

change the 1st and 2nd object to green cylinder and month gear like this

extrude the tiny cylinder from step 1 until it reaches in the big golden gear like this:

i will delete it, if you want this.
************** UPDATE *****************
ok, i am very sorry, i will give up for now after trying it for hours. Maybe i am just to new to Blender....just experiencing with it only for quite a month now.
I show you how far i came...here is my result: (bit more than before, but not really satisfying): https://youtu.be/GX0CTrZW9YY
I changed lots of values like weight, friction and so on. Of course the result was different in many ways. Most of the time the gears just fell off....I enlarged the motor gears which helped a lot for stability, but if it will work some time, then the "too large" gears will collide with each other. As you can see in the side view there is a lot of instability with the gears, maybe another good idea would be to create counter weights so that the gears have more stability. Just to make them with "no weight" did not help either so...
And here is the blend file:

*** UPDATE 2 ****
Hi Alda, please don't give up animation. I am not sure but maybe the mistake are the gears...I changed them and then i got this perfect result for the very easy case of just two gears, which i never got before. Video link: https://youtu.be/La7cIyaCQi8. If you are able to change the other gears  (the blue with its corresponding gear) that they can run smoothly like mine (blend file: ), i will try again for the "whole" solution. Unfortunately i am not the right guy to build nice and working gears ...
**** UDPDATE 3 ****
After thinking about it again i remembered my physics class. Important is the 2nd law of Newton: https://en.wikipedia.org/wiki/Momentum#Conservation
So in real physics your example cannot work - i think.
My idea with the counter weight was not bad - but not enough.
Newton says, you have to have the same momentum on both sides (simplified), so you have to add a second motor on the other side with the opposite direction so that it is in balance again.
To simplify it, i have just copied the first gear with my modifications of above which smoothly runs, so i knew it worked. I copied the motor, empty and the gear to both sides...and...i just can repeat: Blender is just awesome and seems to know Newton well...it is not perfect (maybe i made still some mistakes, BUT it looks much better now...with just physics in Blender!!!)
new result: https://youtu.be/LtknpY4xGAw
it is not perfect, but it runs at least in the beginning pretty nice...until it fells off...right now, i am not sure why, but it is an improvement anyway.


You could try to convert the text to mesh Alt-C in object mode. After that switch to edit mode and select Remove Doubles from the Tools where you can adjust the Merge Distance.


500 samples is really a small number for most scenes. Turn that up to 1500 or 2000 and see how it looks then. There are ways to make more samples render faster, but the only way to really get rid of noise is more samples.

The issue of noise in Cycles has already been covered well in other answers, so I won't duplicate that here. Search the site, and you will find all the information we have to offer.

This answer is the best place to start: How to avoid noisy renders in Cycles?


Can´t open Blender scene and I could last night

Open Window > Toggle System Console , and if it says in the las "missing DNA Block"  ,  it means that your file is now corrupt and this happens because your device wad writing to your blend file while you closed it , so there are 2 ways to solve the problem , one is go to File > Recover > Auto Save and then look for your file and according to the time you last saved , you can open that file , and if you were lucky , you will find your file , and if not , then you can go to your blend1 file and rename it to .blend and then open it and save quickly , now if both methods don't work then " i hope you did not loose much work"


Vertex selection without edge highlighting?

What is or is not shown is in the Properties Region N on the right hand side of the 3D viewport. Untick edges in Mesh Display → Overlays:

You can show/hide vertexes, edges, vertex normals, face normals, etc.


How to fix hair particle shading/topology issue?

I'm not sure I entirely understand it, but what I think is going on is that the hairs are set to have "children" and blender is applying a slight rotation to the kink direction of the child hairs via the "Amplitude" value of the kink curl. Setting the value to 0 removes the strange patterning, as does changing the kink type to "nothing", "radial" and "spiral". The other options still show artifacts. I still can't fully explain it, but at least this should make it "go away", if that's what you're after.


Video Quality Loss after Rendering in VSE

Rendering with the file format AVI Raw should help you retain your Quality ;-)

But if you don't want to have your file sizes explode try H.264 instead.

You can reduce your Bitrate to 5000 for your 720p video. Change your GOP Size to half your Frame Rate.


Very low heat weight of my model after auto weight

If a bone doesn't have full control over part of your mesh, another bone is partially influencing it. Make sure the beginning and end of each bone are touching the mesh, so the automatic weighting works better.

In your screenshot it looks like bones from the left leg are influencing the right leg and vice versa. To get rid of this effect select the left leg in Edit Mode (e.g. go to wireframe, Box select the vertices from the left leg) and then remove the weight from any bone in the right leg or assign it a value of 0. Then repeat the other way around. (I recommend using "Remove")


Blender 2.80 Remove double vertices option gone

Yes, it has been rename to a more reasonable name - Merge by Distance.
Since Remove Double doesn't explain the operator well by it's own name at all. It merges those vertices which are too close to each other by a defined distance.

For developers, the API does't change at all, nothing to worry about it.

In code details
In case someone is curious about why it doesn't remove the double by exactly same position, the problem is that vertices store coordinates (x,y,z) in float numbers, a 32-bit number used commonly in computer science. It is not always precise in manipulating.
For a easy code in Python 3.6.0:
co = 0.1 # Create a 'co' object that gets a float value 0.1
sum_co = 0.0 # Create a 'sum_co ' object thats going to store sum

for i in range(10): # Do the block 10 times
    sum_co += co # Add co(value: 0.1) to sum_co

sum_co == 1.0 # If sum_co exactly equal to 1.0
# Should be true in common sense since 0.1 * 10 = 1
# But the answer is 'False', the sum_co == 0.9999999999999999

Since this situation happens a lot, Blender can't remove the duplicated vertices by exactly same value of the coordinates. Hence, compared by a tiny tolerance is a more common way to deal with this kind of problem. Therefore, Merge by Distance replaces the original name.


Is there a way to find out the last user operation using Python?

The solution for this particular task may be in using render_pre handler to change a global variable. The first frame has to be rendered anyway, so this is not a very elegant solution, but it will do for my purposes. This particular code has to be executed before every render to reset global variable.

import bpy

render_count = 0 # global variable

def execute_for_single():
    print('executing single frame')
    pass

def execute_for_animation():
    print('executing animation')
    pass

def check_for_animation(context, dummy): # needs 2 arguments to be used in handlers
    global render_count # use global variable
    render_count += 1 # change global variable
    if render_count <= 1: # 1 or less frame is being rendered
        execute_for_single()
    else: # more than 1 frame is being rendered
        execute_for_animation()
        render_count = 0 # reset global variable
        bpy.app.handlers.render_pre.clear() # reset handler

bpy.app.handlers.render_pre.clear() # just a cleanup before the start
bpy.app.handlers.render_pre.append(check_for_animation)

Also I found this:

bpy.context.active_operator

It returns the last executed operator, but needs the correct context, which I didn't manage to determine for render operators, even using the context override. But I guess for the most other operators it may be helpful.


Extruding curve and editing non destructively

I don't think you can directly assign two different textures to a curve.
But as a workaround, you can use a Gradient texture.

I'm just mixing two colors, but you can mix any number of shaders/textures...


How do I select parts of my model to independently rotate?

TL;DR
Turning your teeth can be somewhat painful, and the results can be ugly! You have been warned!
Summary:

Go into Edit Mode (Tab).
Make your selection somehow (C circle select, for instance).
separate the object (P).
Go back to Object Mode (Tab).
Move the origin to the center of mass (ShiftCtrlAltC)
Rotate somehow (RR for instance).
optional: fill the gaps.

Walk-through:
It's not going to be an easy job: 3D scans tend to be very messy and extremely dense in terms of vertex count! Also: teeth are usually very close to each other and they don't stand on a perfectly circular base area (so it's impossible to turn them without clashes). But you can try :)
This is a very poor attempt at making a set of teeth: say you want to move the second from the right.

Tab to the edit mode, then navigate (zoom in/out by turning the mouse wheel, turn around by pressing the mouse wheel, move around by holding Shift while pressing the mouse wheel) until you have your tooth "aligned" with the view (use Z to change to wireframe if needed). When you have it from the right point of view, hide all the rest from the view, by hitting AltB and making a rectangle.

Now select your tooth vertices with precision. Use C to enable a "circle select" (you control the size of the circle by scrolling the mouse wheel). Add new vertices, then click the right mouse button to exit the selection, then turn around, press C again, and so on. You can always CtrlZ to undo.

Bring the rest into view by using AltB again. Then hit P > "Selection". This will separate your tooth from the rest of the mesh. You can now exit edit mode: Tab.

Select your "loose tooth", hit ShiftCtrlAltC > "Origin to center of mass". Then use RR to rotate: R then Z will help but only if your model is correctly aligned Z-up.

Unfortunately now there is a gap between the tooth and the underlying surface. Filling it is another level of complexity...
A very rough way would be: selecting both your objects (tooth and the rest of your jaw), CtrlJ to join them. Tab into edit mode. A to deselect all. ShiftCtrlAltM to select the boundaries of the two holes. Spacebar > Bridge Edge Loops to fill the hole. The filling wil be very rough though:


From Blender 2.91, there is now a "compound parent" shape option dedicated to this kind of shape (with concavities):

You can find its description from the release page here.
And in the documentation:

Compound Parent
Takes the collision shapes from the object’s children and combines
them.
This makes it possible to create concave shapes from primitive shapes.
This usually results in a faster simulation than the Mesh collision
shape while also being generally more stable.

The file below is the demo from David Vogel (all credits to him):


Fastest UV unwrapping techique for very large mesh

The built in automatic method that takes the least time to complete is almost always "Unwrap." For a simple mesh of 300,000+ polys, it took about 10 seconds. "Light map pack" took about 20 seconds, and "Smart UV Project" took longer than 1 minute.

For your mesh, I don't doubt that it will take longer, but it shouldn't be hours (I'd think). It may actually help speed up the process to mark some arbitrary seams. If you can, select two points, then choose Select -> Shortest Path. That will give you a contiguous line of edges that you can then mark as a seam. Mark a couple of seams lengthwise to split it into dorsal and ventral halves, then maybe even into quarters. Splitting things up this way, usually helps "Unwrap" work faster, but doesn't have any effect on any of the other methods.

Hope that helps!


How to search for the 'double click' shortcut?

I don't think you can search for a hotkey using double click in the latest version of Blender (2.79b). I created one using double click but even searching dbl-Left Mouse didn't work (which was displayed in the key binding area). Maybe it has something to do with not being able to assign a double click shortcut by double clicking.


How to offset the start of rigid body physics to a specific frame

To offset when a rigid body simulation starts, I would suggest that you use keyframing to your advantage. You can keyframe any option in blender, including the "Animate" and "Dynamic" check boxes in the rigid body options. Mouse over the "Animate" or "Dynamic" checkbox and press "i" like any other add keyframe.

You can then make it so that only when the object is hit, or at a certain time, will the object begin to fall. Likewise, you can also use this so that your fractured objects do not fall apart until they are hit or about to be hit. Hope this helps!

P.S.You can find a full tutorial detailing this sort of animation/simulation here. This is a three part tutorial (with a prequel teaching how to model the mug) made by Blender Cookie.


There's no direct way to move layers around from the UI.  I think the best you can do is select the source layer (either clicking in the properties panel or using the ShiftM popup), use A to select all bones, and then M-ove them to the destination layer, assuming the destination layer is empty.  If you are trying to swap two layers "X" and "Y", you need to move all the bones in "X" to a spare empty layer "Z", then move "Y" to "X", and them move "Z" to "Y".


Painting aligment and texture bleeding even with margin turned on

In the Options Tab in Texture Paint mode you can set the bleed to 0; I do that here and get something like you might be looking for.


Well, you have a few options.

Freestyle creates a line around the edge of all your objects soon render. You may be able to tweak the settings to create the chalk like effect.

Grease pencil is also another option. Can be harder to accomplish but you have more control over the lines.

The last option I have is to use a flat plane and tweak texture settings with clouds to create a brush like stroke. Again, difficult and a hassle but could produce some great effects.

If you want any help on how these may be completed I will try and help where I can.

Torus Test:

EDIT:

This is how I created the torus effect above as requested.

Firstly, create a copy of your item slightly larger than your original. The gap between the two will determine the size of your outline.

Create a circle with the triangle fan fill. The number of vertices is your choice, the higher the count, the better the effect will be but performance will be reduced later. I used 128 for mine.

Go to edit mode.

Select the edge ring and delete all the edges, leaving lines spraying from the centre vertex.

Select everything and extrude to create a pretty cool looking mesh.

Select the centre edge (Done by selecting the two centre vertices) and go to Edge-->Edge Split.

Go back to Object mode

This is where thing may get slow for a bit!!

Add a Solidify modifier and set the thickness really low. I set mine to 0.001.

Add a boolean modifier set to intersect. Choose your slightly larger, copied object for the boolean modifier object. Hide your copy object

Now you should see lots of thin lines around the outside of your mesh as shown below. note as they rotate around they get thinner and disappear.

On my torus, I did not need to do this step for this rotation, but if the centre vertex is showing all clustered together on your meshes surface like below, add a subsurf modifier to the top of your modifiers and set it to 1. this should leave a bit of a hole where the vertex was. BUT DONT WORRY!!! we will fix that soon.

More LAG Ahead!!!

Copy your outline object and duplicate it. Rotate it 90˚ on one of the other two axis' so the lines face in a different direction. Note the small hole on the righthand side due to the subsurf modifier. This will be better hidden with the textures. I do have a small glitch (The plane protruding from my mesh) but it is almost unrecognisable in the render. plus you can delete it once modifiers are applied.

Hide both of these outlines for now if lag is getting the better of your machine :D

Time for a material. I have taken an image of mine below. if you wanted you could use a texture, but I have gone for a procedural noise texture.

Show your two items again and apply the material. Take a look around in render view. My nodes are set for cycles, so some tweaking may be needed to use in EEVEE.

If you are happy with the results, apply your modifiers IN ORDER!!! and you will get your results in mesh!!

This works by the layering of faces adding their translucency to each other slowly darkening the view. The more layers overlapping, the darker the edge. This does create a little bit of darkening towards the center but when set low like mine it is relitively unoticable.

TADA!

Note that I did this on an early 2015 MacBook air which has relatively low computing power compared to many 3D designers laptops and common desktop PC's. My computer started running quite slow when using the boolean modifier caping my limitations but you may be able to take the number of verticies up in your model.

Good luck with your project and I hope I helped.

BFB


Select vertex in UV map based on coordinate x,y

I propose to use a kdtree so that we'll have an efficient search tree over the UV Map, for all the coordinates you have in input.

The principle is the following:

Create a kdtree and populate it with UV coordinates
Initialize it
Search on it from the input coordinates you have
From this index, get the corresponding vertex index (in the 3D mesh) using the loops

The tree is initialized once per mesh and allows multiple searches.

The commented code:

import bpy
import bmesh
from mathutils import Vector
from mathutils.kdtree import KDTree

print( '-------------------------------' )

# Do all that in object mode
bpy.ops.object.mode_set(mode = 'OBJECT')

# Get the mesh
obj = bpy.context.active_object

# Get its UV map
uvmap = obj.data.uv_layers['UVMap']

# Make an array of uv coordinates in 3D
coordinates = [(d.uv.x, d.uv.y, 0) for d in uvmap.data]

# Create a jd tree from that
kd = KDTree( len( coordinates ) )

# Populate it
for i, v in enumerate( coordinates ):
    kd.insert( v, i )

# Initialize it
kd.balance()

# Input UV coordinates
x = 0.41
y = 0.96

# Search
coordinate, index, distance = kd.find( (x, y, 0) )

print( coordinate )
print( index )
print( distance )

# Corresponding vertex (in the mesh) and its index
vertex_index = obj.data.loops[index].vertex_index
vertex = obj.data.vertices[vertex_index]

print( vertex.index )

Note: there is also a bvhtree version in the blend file. If you have time you could compare the results and perfomence

The main diff between bvh and kd is that bvh will test on faces and kd will test on vertex proximity (so this can be outside the face).
I don't know what is important in your context.

In the blend file, there is two script in the text editor 'KDTree' and 'BVHTree' so that you can choose.


Is there any way to get single pixel wide aliased lines?

If you're ok with using the Workbench engine, you can simply go to User Preferences → Viewport → Smooth Wires and disable Overlay.

You can choose the Workbench engine just like Cycles or Eevee in the Render Properties tab, and since frames can still be rendered with transparency you could easily composite them into frames rendered with any other engine.

Result


Is it possible to use more than 20 layers?

No. A Scene object only contains exactly  20 layers, no more, no less. But if you mean render layers, the upper limit is 32768.


Curve Spiral creates unwanted result with mesh

The problem could be solved simply by tilting the curve a bit. The to me previously unknown shortcut ctrl+t allowed me to tilt the curve in such a way that it worked out in the end. For those that don't know: tilting a curve doesn't move any of the points on a curve but changes the direction they are facing.


Yea in the end it was normal map problems, no clue why the hell the normal map from cage does not work at all but I just baked normal map form high and low poly mesh, and that fixed most of the shadow problems(after I flipped the green in the texture in UE4), took me whole 3 days to fix this god dammit, but at least I know how to bake normals now -_-...
Thanks for trying to help me.


How to make wireframe mode in 2.9 look like 2.8's version

Switch to wireframe mode, click the top right viewport shading dropdown menu and change the X-Ray value to your liking, the higher it is the higher the opacity of the wireframe will be.


Why doesn't the Graph Editor show my keyframes and connecting lines

The screen shot is a little low res, so it's hard to see.

Your keyframes in the dope sheet are in the 340 to 410 range but the graph editor is set to show the -200 to 200 frame range.

I think if you press the Home key while the cursor is in the graph editor the view should zoom to your keyframes.

Alternatively your keyframes are simply out of view on the y-axis of the graph editor and the Home will also solve this.


Is there a way to hide bones that don't have vertex groups

Weight is a property of vertex groups, so you can't have an automatic procedure to select and hide bones with or without weight. Anyway you can manually move all unwanted bones in a separate bone layer (M in pose mode), and make this layer visible or invisible.


Sadly you cannot turn off shadows for emissive material or the world background.

You can control the shadows of any object in that objetc's shaders using the Light path Shadow ray input or by unchecking the Shadow option under Ray visibility in Object panel, but that reacts to all light sources.

The only solution is to use Light primitives, for which you can turn shadows on/off. If you create a big dense icosphere and you put a point-light in every vertex, you get a sky dome with even light distribution.

Using python you can access the HDRI texture pixels and drive every light's strength and color to match a point on the texture accordingly. How the pixel array works is explained here and figuring the math of turning a point on a dome into 2D point on texture is a matter of some trigonometry. You can use a script to be run once and set this for all the dome lights.

You can also add drivers to link and multiply the strength of those lights with some Scene property for better control. How to create drivers with python script is here.


After reviewing the exporter and Max importer, I found out that the correct way is to reverse the bone tips in Blender when comming from Max.

new_bone.parent = parent
new_bone.tail = parent.head
new_bone.use_connect = False

Also, the model cited in the question is kinda broken, so...

Tested with other models and everything looks fine.

Thanks, lemon, for the input.


How to know if it's a good or bad retopology?

you topology seems good, but i recommend to smooth/relax some of those edge loops in the back/shoulder, and additionally you can improve a bit the shoulder edge flow like this, also a add more captures of the head and other areas if you can... remove some unnecesary edge loops in some areas can help too, addtionaly when you rig this check the preserve volume option in the armature modifier, and add a smooth corrective modifier below with the default setting should be fine, and then also add 1 level of sub-div modifier below of that one, then it should be fine for animation, also remember to avoid 6 vert poles in your model, also the model has to be all quad based as possible (you can leave a few triangulates in some areas, the subdiv modifier will erase it) to use the subdiv properly


smoke+fire simulation fine in viewport but jittery in render

I fixed the problem by disabling "Smoke Adaptive Domain" in the Physics tab in the Properties panel, while selecting the domain:

For whatever reason, this caused the domain to shake around a little bit, causing the jittering. I'm still not sure why it doesn't jitter in the viewport but does in the final render.


Blender VSE (VideoSequenceEditor) Slows drastically when adding strips

There is not really a fix for something like this. You can sequence it overnight, but there is no way to speed it up unless you set the output to a lower quality


General Tips
A few general tips regarding Bezier Objects and the Curve modifier.

For an easier time set curve origin to one of its ends, preferably its starting point.
If necessary under Edit Mode invert spline direction so the start point is at the same end as the origin
Place both the curve and the deformed object at the same location in the scene so that both center match in world coordinates
Make sure both objects have matching rotations on all axis. Clear rotations beforehand, correctly orient your mesh, and then apply all rotations in Object Mode. After adjust as necessary, rotating both curve and mesh in tandem.
Apply scale on both objects. Having uneven or unmatching scale factor will lead to issues.
Make sure curve bevel radius is uniform and at a value of $1$, anything else will introduce distortions.
If you scale your curve in object mode, even if you apply the scale, clear your bevel radius by setting them all back to $1$ in edit mode. Applying scale doesn't clear the bevel radius.
Make sure your mesh extends in the same direction the curve object, growling along its side, otherwise it may produce no visible results.

Non of these steps are strictly necessary, but they certainly help get more predictable results. Unless you know what you are doing these will help get started.
After a workable starting point you can adjust as necessary, breaking any of the above points you deem necessary yo get the desired results.
In your particular case
First you should sanitize both your curve and your lights object. Correctly place your lamps exactly at the origin of the curve, clear its rotation, and then rotate it again so it faces the desired direction. After that apply the rotation.

There are a few types of different curve objects in Blender, Bezier Curves, NURBS Curves, or Poly Type curves. Since you converted from a mesh object it is by default a Poly type curve, which has no curvature and hence no handles. It can only contain straight "poly line-like" segments.
This has absolutely no influence in your curve modifier bad results, and can easily be fixed by changing curve types. Under curve edit mode use the button on the toolbar that reads Set Spline Type > Bezier.

After that make sure you then change all handle types to Automatic or something other than vector to get a smooth curve.
Then you can finally activate the curve modifier. Switch its direction to Xaxis.
Anyway, the root cause of the weird results you are getting in this particular case are caused by having your curve vertex with a very small Radius factor, causing the mesh to be scaled along the curve. You can fix this by entering edit mode on the curve, in the Properties Shelf > Transform > Radius set it to 1 on all vertex. You can quickly override all selected vertex with the operator Set Curve Radius.


How can I improve viewport performance when using Dyntopo?

Here is an answer by Sanctuary from Dynatopo test thread:

Some performance tips about Dyntopo

Do not use Matcap, while it does not show while you're still blocking out your sculpt and you are in early stage of it, Matcap will very noticably impact performance when you're starting to reach mid/high poly . Use that addon instead , gives full control on the Blender existing opengl lights and does not impact performance.
Make sure you have Double Sided disabled in the Object Data panel, it's not a nvidia problem only, at higher poly stage the difference in performance with it being enabled or disabled is very noticable on every hardware.
Check the Detail level in the Dyntopo setting, too low (like less than 5) that can lead in a -very- lot of triangles generated by your brush strokes , while sometime you may want that, in other time that amount of tris could be really unneeded and can degrade performance. For most of the sculpt time getting detail between 15/20 is good, and for fine detailling, around 10 or a bit less should be enough (remember that when you zoom in you're fine detailling anyways)
Less than 10 can be really overkill due the amount of generated tris.
You can optimise some part of your sculpt for which you think there are way too many triangles (enable Wire + Display All Edge to see what's going on while you sculpt) by either enabling the Collapse Short Edges button , increasing the detail setting and enabling for your brush the "Simplify" tool (in the bottom header Brush -> Sculpt Tool -> Simplify
You can press H and drag a selection to hide those parts while in Sculpt mode, it can help performance really a very lot depending on the kind of polycount you're having of course (ALT+H to unhide)
some people have mentionned that the regular freeze/pausing could be related to Blender autosaving (a function enabled by default for each 5 minutes) , you can disable or change the delay for that in File -> User Preferences -> File
additionally in freeze/pausing moment, clicking on "Optimise" in the Dyntopo settings may help so it recalculate whatever it has to recalculate
If rotating/zooming the view become painfully slow, press Z to switch to wireframe, rotating will then be very fast, press again Z to switch back to solid shading
Dyntopo can't currently reach (while keep performance good ) the same kind of polycount you can reach under Multiresolution, fortunately the "detail where needed" system of Dyntopo generating topology only where you work allows for detailled sculpt at a much lower polycount than an equivalent multires would require.
So don't be surprised if you can get a workable million in Multires and an unworkable million in Dyntopo.
Of course powerfull computers will get higher than less powerfull ones (and if i remember well, Dyntopo isn't multithreaded, while Multires is multithreaded).


How to cast the shadow of the texture's alpha channel and not the actual geometry of the plane?

Blender internal can be a bit confusing in that regard. The objects casting the shadows do not determine how those shadows are received in other objects. The receiving objects determine the quality of the shadow.

By default the receiving objects show the shadow of the pane, not of the texture.

The receiving objects  (in your case the ground plane) have to be set to receive transparent.


How to execute python code after each stroke painted in image editor?

You can achieve this by using a scene update handler that monitors the state of the active image in the image editor.

For this technique to work you need to:

Create or open an image in the image editor window on the active screen.
Save your image to an external file once.
Also: the script will save any change to file immediately. If you don't care about that, this solution can work for you.

The example below illustrates how you can set a new random paintbrush color after every stroke.

import bpy, random

def run_if_img_changed( scene ):
    im = None
    # References the active image in the image editor
    for a in bpy.context.screen.areas:
        if a.type == 'IMAGE_EDITOR':
            for s in a.spaces:
                if s.type == 'IMAGE_EDITOR':
                    im = s.image
                    break

    if im and im.is_dirty:
        ## Replace the bit in this if clause with your code
        print( "Image changed!" )

        # Set paintbrush to random color
        bpy.data.brushes['TexDraw'].color =  [ random.random() for c in 'rgb' ]

        ## End of replaceable sample code

        # Save image so it will no longer be dirty
        im.save() # This line will crash the script if you haven't saved the image to a file yet

bpy.app.handlers.scene_update_post.append( run_if_img_changed )


How to ignore naming index in modifiers?

There are (at least) two ways to approach this, either you can differentiate the modifiers through their name or their type.

Filter by Prefix

If you want to filter them by a prefix you could use the following approach to retrieve references to the modifiers.

First, get the modifier collection of the object. All (key, value) pairs can be accessed through the .items() function. The keys are the names of the modifiers, therefore these have to be checked for a prefix match. Python has the .startswith() function to check if a string starts with a given prefix. If a match is found for a key, the corresponding value is one of the modifiers you're searching for. All of this can be combined to a list comprehension as shown below.

import bpy

prefix = "Subdiv"
modifier_collection = bpy.context.object.modifiers
modifier_matches = [modifier for key, modifier in modifier_collection.items() if key.startswith(prefix)]

print(modifier_matches)

Filter by Type

Sometimes you may not know the name of the modifiers, since these are user editable, but you may know their type. Searching for modifiers by their type can be accomplished by getting all modifiers of the object through .values() and then checking if they are of a certain type, e.g. SUBSURF in the example below.

import bpy

modifiers = bpy.context.object.modifiers.values()
modifier_matches = [modifier for modifier in modifiers if modifier.type == "SUBSURF"]

print(modifier_matches)

The example below shows how to iterate through all modifiers of an object, check if its name starts with a given prefix and if it does, disable it for rendering by setting show_render to False.

import bpy

for key, modifier in bpy.context.object.modifiers.items():
    if key.startswith("Subdiv"):
        modifier.show_render = False


How to enable and disable Add-ons via Python?

There is an API to manage addons to bypass operators, see addon_utils, this isn't exposed in the API docs because its mainly to manage internal functions. But the API is quite stable now.

addon_utils.enable(
        module_name, default_set=False, persistent=False, handle_error=None)

addon_utils.disable(
        module_name, default_set=False, handle_error=None)

Typically its enough to call:

import addon_utils
addon_utils.enable("my_addon")
addon_utils.disable("my_addon")

Use default_set if you want the value to be stored in the preferences, (although these will have to be saved for the new configuration to be used on restarting Blender).

See the docstrings in the source:
https://developer.blender.org/diffusion/B/browse/master/release/scripts/modules/addon_utils.py

Since you ask about reloading, see this question on recursive reloading.

https://stackoverflow.com/questions/28101895/reloading-packages-and-their-submodules-recursively-in-python


How to merge two characters imported from MakeHuman

You can parent ctrl + p one of the models to the other or both of them to an empty. And then the transformations should be applied to both of them.

https://www.blender.org/manual/editors/3dview/relationships/parents.html


I usually start with a Wave Texture set to ring. Since the door is made from many parts, it should be uv unwrapped to reflect that, or copies of the material made per board so the grains can be different. The position of the ring, and scale, is set using the mapping node, and the output fed to a color ramp, which feeds roughness in the principled BSDF. The original ring output can also be used to control a second noise texture to add the lines.


Texture not being shown in rendered animation

Never mind about posting the new blend file. The reason your texture is not showing up in the render is because you have an override material set in the RenderLayer screen called "Material". It's an empty material which is why the object is rendering as white.


Perhaps it's just a face in another object?

Maybe provide your .blend so we can investigate quicker.


Random sized cylinders with no intersection/gaps

Here is a basic way you can fake it.

Create a new box mesh object that should be large enough to encompass a simulation covering an area big enough to produce the desired patterned area.

This Box would ideally be flat, narrow in one direction and large in two others (like say 10 x 10 x 0.2 units).

In the physics tab set it to Rigid Body, Passive and Shape two Mesh.

Then create a Cylinder mesh, rotate it in Object Mode 90º about the X axis so it lays flat. Set its physics properties to Rigid Body, Active and Shape to Cylinder. Make sure the physics bounds cylinder aligns properly to the mesh geometric shape.

Now add some constrains to it, so it won't rotate about an axis we don't care about. Add a new Limit Rotation constraint, then turn on the options Limit X and Limit Y only, and change the space to Local Space.

Clone-duplicate the cylinder around and place all copies in an array-like grid, along the top of the box, making sure they all fit completely inside the previously created box.

When seen from the top the cylinders should be tall enough to barely fit the box, and the box should be narrow enough so the cylinders are tight but not too close, which would cause problems with simulation precision.

To make cylinders have random size by selecting one of them, turn on Proportional Edit, switch the Fallow Type to Random, then scale one cylinder with S.

While scaling press Shift+Y to exclude scaling along the Y axis (so the cylinders all maintain the same height and still fit tightly in the box), and while editing scroll the mouse wheel to control the influence radius so it encompasses all cylinders. Make sure you hide or lock the box beforehand so it is not affected.

Adjust scaling as desired to create the amount of variation you see fit. Scale multiple times if necessary to achieve a larger range of sizes.

Now play the animation with Alt+A, to cache the physics simulation. You may also need to adjust the Rigid Body World properties in the Scene tab of the Properties Window, like increasing the Steps per Second and Solver Iterations.

Let it play for a while after falling, so the simulation settles down. The end result should be what you desire.

You can then optionally apply physics if you want static objects with actual position, or join them all into a single mesh. You may also remove one end of the cylinders so you get a "2D" flat pattern.


This menu from left doesnt work anymore, is always greyed out

If you start doing things like rotation or location, the settings won't be available anymore.

Note sure if it's your case here but maybe try to first create the cylinder with shift+A then go directly to the settings, do whatever you want there, and the only locate rotate or scale it.

Hope it will help


To make an edge between two vertices press F. If the vertices are on opposite sides of a face you can instead use J (for join).

To add a vertex, select the edge. Use Subdivide from the Edge menu.

To slide the vertex along the edge double press G.


How do you rotate an object so that a particular face is parallel to the ground?

Not sure if there is a more efficient way to do this but the method I most frequently use is through an auxiliary empty object to snap to the surface.

Add a Plain Axis Empty to your scene
Activate Snapping and Align rotation with the Snapping Target
Align the empty with the part of the surface that is to become the base
Now you will have to manually copy the three axis rotation from the empty to the object inverting them. That means if your empty's rotation is 10,50,30 you will have to paste in your target object -10,-50,-30
Apply the rotation to your object

Adjust it accordingly to fix the orientation by rotating 180º in needed axis.

Side note: It is usually helpful if your "flat face" that is to aligned to the ground is slightly subdivided so there's a few extra vertex for Blender to snap to.


When using Rigify, Is there a way to add more bones to the lips?

You have to generate the rig first, then you can modify it as you want: better adding bones, withouy deleting or dividing anything, unless you know exactly what you're doing, because Rigify rig is quite complex, with lots of auxiliary and machinary bones.


Using three js exporter in a python script

I'll ignore the part of your code which you seem to have working. MrDoob advised in the readme to use the exporter available from the Three.js github repo. It's tucked away in a directory.

github.com/mrdoob/three.js/tree/master/utils/exporters/blender/addons/io_three

If you are using the one that comes with Blender it may not be up to date. Working under the assumption that you're using the latest and greatest (from the link above), then something like this will export the active object.

bpy.ops.export.three(filepath="/home/zeffii/Desktop/barbaric.json")

If you have specific options to pass then they must be passed as keyword arguments. Use Python Console's auto-complete to get the full list or read the source of the exporter.

>>> bpy.ops.export.three(
three()
bpy.ops.export.three(
    filepath="",
    check_existing=True,
    option_vertices=True,
    option_faces=True,
    option_normals=True,
    (...)
    option_influences=2)

Enabling the add-on via a script is a separate issue from running the operator. If you are really stuck it may just be simpler to store that preference in the startup.blend. If you run the script and Blender hasn't yet loaded the add-ons then you may want to read this how to enable addon via script.

I took the liberty to rewrite/augment your script, I think this does (in an admittedly awkward way) what you wanted.

import os
import bpy
import addon_utils

def clear_scene():
    bpy.ops.object.select_all(action='SELECT')
    bpy.ops.object.delete(use_global=False)

def main(filePath, fileName):
    clear_scene()

    fullPath = os.path.join(filePath, fileName)
    bpy.ops.import_scene.obj(filepath=fullPath)
    obj = bpy.data.objects[0]

    # find dimensions and scale accordingly
    dims = obj.dimensions
    scale = min(10 / dims[0], 10 / dims[1], 10 / dims[2])

    # set cursor to world origin, and set object-origin the same
    bpy.context.scene.cursor_location = (0, 0, 0)
    bpy.context.scene.objects.active = obj
    bpy.ops.object.origin_set(type='GEOMETRY_ORIGIN')
    obj.scale = (scale, scale, scale)

    json_fileName =  fileName[:-3] + '.json'
    finalPath = os.path.join(filePath, json_fileName)
    bpy.ops.export.three(filepath=finalPath)

def ensure_addon():
    try:
        addon_utils.enable("io_three")
        return True
    except:
        print('failed to enable io_three')
        return False

def path_iterator(path_name, ftype):
    for fp in os.listdir(path_name):
        if fp.endswith(ftype):
            yield fp

if ensure_addon():
    filePath = "/home/zeffii/Desktop/Objs"

    for fileName in path_iterator(filePath, '.obj'):
        print(fileName)
        main(filePath, fileName)

To clarify my changes / thoughts.
The obj import doesn't place the object in the active state, just selected. The export feature seems to require the object to be active, and ignores objects that are merely selected. To take care of that, use the reference to the only object in the scene and set it active:

bpy.context.scene.objects.active = obj

The error message, context is incorrect, is in this scenario a poor error message. (if the above is genuinely why the initial code failed.. )


Why does my grease pencil's filled outline turn black in render preview?

okay so I figured out that I needed to change the vertex color to the color of the outline. I just needed to open the materials tab and drag and drop the outline color to the vertex color, then things actually started to look right. Also, another way to do this,(and easier) is to turn on paint mode to material. This will use your material base color to paint instead.
oh, and one more note to add here, the drawing doesn't change, you have to draw with it to see the difference. It was a little confusing and frustrating because I have to redraw my frames now with this new setting, but I'm glad there's a way to fix this.


how do i insert a keyframe at the frame where the object reaches a path control point?

Not sure if it helps, but if you don't mind loosing the constraint itself (you can easily restore it if needed anyway) you could bake the action into keyframes.

That way you get an already drawn graphic of the object positions along time, and you get a better visual feedback of where the object is and when.

Keep in mind that this will not automatically give you keyframes and the exact curve control points, but the position graphics might give a rough idea of where tight turns are.

That way you can then easily accelerate and decelerate the animation by nudging frames back or forth in the graph editor.


can you delete keyframes at regular intervals in a given range?

It's not exactly what you're asking for, but maybe it can help : there is an (integrated) addon, Simplify Curves. It reduces the number of keyframes, preserving the general shape of the curve.

Activate the addon (search "simplify" and click the checkbox next to "Add Curve: Simplify Curves")
Select your F-curves
type Spacebar then "simplify", select "simplify F-curve"
adjust the "distance error" setting. Warning, it's located in the Operator panel in the 3d view, not in the F-Curve editor


I was just searching for an answer to the same question. If the particle system is unused by any object Blender will delete it on quit. However sometimes in complex scenes it can be hard to find the object that has the particle system.
You can remove it in the Outliner workspace by selecting Blender File  to display file data and linked libraries, under Particles you will see all your Particle systems and you can Right click and delete them.


One cause of these artifacts may be hidden, but "set as to render", objects. If some of their faces might overlap to your active object during the baking.

Even your high poly object can cause this if you don't correctly enable the option "bake selected to active".

Example:

Low and highpoly

Object are in the same location, so faces overlap themeselves or are occluded

Image above is the baked with with the option disabled

This is if it is enable. You must select the highpoly, and THEN the lowpoly in order to get this result.

Someone asked for a moon? :-)


Rigify - How do I change 'Bend Rotation Axis' parameter using Python?

Figured it out:

 bpy.data.objects['metarig'].pose.bones['thumb.01.L'].rigify_parameters.roll_alignment = 'manual'
 bpy.data.objects['metarig'].pose.bones['thumb.01.L'].rigify_parameters.copy_rotation_axes = [True, False, False]


Exporting fbx animations includes Garbage (UE4)

Even without Rigify you get junk animation tracks. At least I get in my own hand made armatures. But what I do is keep an eye open in the NLA editor if there is any animation on objects I remove their tracks.

I'm gonna try and explain NLA and also FBX export to UE4 here, at least as my workflow goes.

I always create new action before I start animating to keep the "root" timeline clear. Open Dopesheet Editor, and switch to Action Editor (yellow cube icon). In this case Jump_1_End. Once done click the (F) to make a fake user and then the dubble down arrows (in NLA editor or to the right in header) This will save the Action to a NLA Track (you can rename them, something better than NLATrack.001 etcetera. I did rename my NLA Tracks to my Action Set name.)

Export to FBX, I use the default settings exporting both Action and NLA Tracks as separate Anim Tracks in FBX file.

You can check your export in Autodesk FBX viewer, I do this often to check that export from Blender and import in UE4 is correct. Somehow Unity can read .blend files and get Action animations without pushing down to NLA tracks and no junk data. How they do it, I don't know. I wish UE4 could read .blend files also :)

Anyway here you can see junk anim tracks, try and clean up in Blender by removing animations on objects etcetera and just have NLA track and Armature animations. To keep the junk animations to a minimum.

Drag and drop, or import how you want. But drag-n-drop requires you're hovering a couple of seconds with the FBX file in the Content browser. Once loaded (just went with default settings, it could find the skeleton and all) I clean up and remove the unwanted animation tracks. This works for me, in time I might find a better way. It's not super beautiful, but it gets the game done.

in the NLA Editor in blender you can stack and repeat animations this is good for checking loop points and maybe just have a overview of your animations before exporting. I use this for mock-ups sometimes. You can also blend NLA Tracks when doing longer animations, but in this scope. Game asset creation, you kinda just want to have each Action set in a separate NLA Track layer to get all animations into UE4.

To check your animations on your armature mesh, or skeleton mesh in UE4 you need to make a animation blueprint with simple blueprint logics, there are other tutorials on the internet on this and since it was not your question check unreal engines youtube channel.


Why are blender console and info window values different for the same object?

You'll notice that the property window only shows three decimals of precision.

If you round 0.43689292669296265 to three decimal places, you get 0.437.
They're both accurate, but one is more precise than the other. If I were you, I'd choose the one that's more precise. Note that you can put the very long number into the field in the property window, but it'll get rounded.

In short, always choose the referenced value, not the displayed value. The interface is getting a number from somewhere, and then formatting it for display to the user. Instead of using a value that's being modified to fit nicely in a field, you should reference the same value that the interface is referencing.


How do I put my Body group into my Armature group?

Make sure to click and drag the ICON next to the group name. Not the TEXT.

Click and drag the ICON of the group onto the other group.


Facing the same problem now, really confusing, but I've just found a solution.

Normal maps contain non color data, and when baking normal map images (e.g. by shader emission, when noncolor is enabled) doesn't gives you what you expect.

You should enable color for each normal map images for baking as a diffuse or emission (of course it changes preview result).

Note that it will not yield exact results, but very close to original, maybe because I'm not using EXR, but I'm fine with the result.

English is not my first language so I hope its understandable.


Lens settings missing from camera settings

This was a bug in an early pre-release version of Blender 2.80 which was fixed in February 2019.

https://developer.blender.org/T61499
https://developer.blender.org/rB5e3838faa2e6dae0ac52860085f5dc4b7a000ea5

You should at least update to the proper release of Blender 2.80 or, if your hardware supports it, the current long-term support (LTS) version Blender 2.83.6 or the most recent release Blender 2.90.
The LTS is a version of Blender that will continue to receive bug fixes for a span of 2 years after its initial release, while the 2.90 release will be superseded by 2.91 in November 2020.

The Blender LTS program is aimed at ensuring that long-lasting
projects can be executed using a stable Blender version, which will
provide critical fixes throughout a 2-year time span. The LTS version
will not have any new features, API changes or improvements. Any
critical fix that is applied to the 2.9 series will be regularly
ported over to Blender 2.83 LTS.


You can import chart to Graph editor with an add-on you refer to.
It is fixed now by Chebhou :) You can download script from here.
Add-on appears in a Scene properties panel and works as expected in 2.74 (seems to me).


As this hole is supposed to help to open the bottle, I suppose you've made a mistake and that the topology is rather something like that (I've separated the plug to make it more understandable):


My hinge simulation is not working correctly

From what I can tell, it appears that your setup has a number of issues (and please correct me if I am mistaken on anything here). The biggest one being that the physical design of the flaps and how you want them to open is impossible. I could try to explain it, but the gif below will show it best (I realize it's upside-down from what you want but the concept still applies).

If you tried to do this setup in the real world, the flaps would be locked in place and unable to move, as in the gif you can see that as soon as the flaps move they intersect with the walls of the bottle.

The solution to this will depend on your end goals. If you need the flaps to be visible, the only solution that I can think of would be to move the hinge to the middle of the bottle so that the flaps would fold up and meet in the middle. If you just want to keep two fluids separate and have them mix when the bottom one is forced up, there is probably a better solution for that, but I would ask a new question if that is your goal.

A couple of other things that I see that would also cause problems, even with a proper setup, are that the flaps start out partially inside the walls of the bottle. This will always break a simulation as it's a physically impossible condition. The second is that the bottle collision type is set to Convex Hull, which isn't the best for shapes with large convex areas. A better collision type would be Mesh, as it is the most accurate.

However, these are in addition to the main problem, and likely won't help unless the entire system is redesigned.


One way to do this is by select everything with box select (B), circle select (C), or lasso select (⎈ Ctrl LMB) while in solid view with Limit selection to visible enabled, then inverting the selection (⎈ CtrlI) and deleting faces:


How to import a .raw model into blender?

Assuming you are using a relatively recent version of Blender, did you try opening the User Preferences editor (CTRL ALT U), selecting the "Add-ons" tab, scrolling down to the selection

  Import-Export: Raw mesh format (.raw)

and clicking on the button at the extreme right, to activate the add-on?

Did you then click the Save User Settings button in the lower left of the editor window to save the activation of the user preferences? If so, then you should be able to open the File menu in the info window, and find the ability to import and export files in ~.raw format in the appropriate sections of the menu.

I don't see where you show the version of Blender you are using in your question, but the add-on has been part of the Blender distribution since at least version 2.63a.


How to play multiple tracks in video sequencer?


How to get a smooth transition between two objects. Two perpendicular cylinders

create a lip to the connecting piece
assign a vertex group to the lip vertices
add the Shrinkwrap Modifier to the handle, selecting the other cynlinder as target and using the created vertex group play around with the Mode to suit your needs).


Script or Command for selecting Adjacent Faces in Blender (see image)

Bmesh and sets.

Use sets because there will only be one instance of an item.

One set is our selected faces.

For all the vertices in each selected face, look at the link faces loop (all edges connected to that vert) and add any face that isn't  already selected to another set.

import bpy
import bmesh
context = bpy.context
ob = context.edit_object
me = ob.data
bm = bmesh.from_edit_mesh(me)

sel_faces = set(f for f in bm.faces if f.select)

grow_faces =  set(fs for f in sel_faces for v in f.verts for fs in v.link_faces if not fs.select)

for f in sel_faces:
    f.select = False
for f in grow_faces:
    f.select = True

bmesh.update_edit_mesh(me)

Note: For keypress operation convert this into an operator, because I'm feeling generous here is above pasted into Text editor > Templates > Python > Simple Operator

import bpy
import bmesh

class SimpleOperator(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "object.simple_operator"
    bl_label = "Simple Object Operator"

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

    def execute(self, context):
        ob = context.edit_object
        me = ob.data
        bm = bmesh.from_edit_mesh(me)

        sel_faces = set(f for f in bm.faces if f.select)

        grow_faces =  set(fs for f in sel_faces for v in f.verts for fs in v.link_faces if not fs.select)

        for f in sel_faces:
            f.select = False
        for f in grow_faces:
            f.select = True

        bmesh.update_edit_mesh(me)
        return {'FINISHED'}

def register():
    bpy.utils.register_class(SimpleOperator)

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

if __name__ == "__main__":
    register()

    # test call
    bpy.ops.object.simple_operator()


Changing the specular exponent of Principled BSDF with texture when exporting to Wavefront (.obj)

The roughness of the Principled BSDF controls the specular exponent that is written into the .mtl file.

From the export_obj.py source code:

# XXX Totally empirical conversion, trying to adapt it
#     (from 1.0 - 0.0 Principled BSDF range to 0.0 - 900.0 OBJ specular exponent range)...
spec = (1.0 - mat_wrap.roughness) * 30
spec *= spec
fw('Ns %.6f\n' % spec)

Output for Roughness set to 1.0:

# Blender MTL File: 'None'
# Material Count: 1

newmtl Material
Ns 0.000000
Ka 1.000000 1.000000 1.000000
Kd 0.800000 0.800000 0.800000
Ks 0.500000 0.500000 0.500000
Ke 0.0 0.0 0.0
Ni 1.450000
d 1.000000
illum 2

Output for Roughness set to 0.0:

# Blender MTL File: 'None'
# Material Count: 1

newmtl Material
Ns 900.000000
Ka 1.000000 1.000000 1.000000
Kd 0.800000 0.800000 0.800000
Ks 0.500000 0.500000 0.500000
Ke 0.0 0.0 0.0
Ni 1.450000
d 1.000000
illum 2


Cannot rip multiple disconnected vertices

I think your problem is that you select all edges which together constructs a face, thats not possible, you have to unselect one edge to Rip that face, but then its same than Split-command to face.


I need to turn one side of a cylinder into a square a leave the other side round

Don't know if this is what you wanted, but you may just bridge the vertices between square and circle to create this kind of shape. Add a plane and subdivide it as many times as you want. Then add a circle with the number of vertices matching the number of the vertices on the edges of the square/plane. Finally select them as pictured below, press Spacebar and type Bridge-->Bridge Edge Loops.

NOTE: There is similar answer about this here on BSE, but I can't find it.


I tried your file: all fine! Unless I'm missing something, I suspect that you just press ALT-A or press "play" button and nothing happens... because you're starting at frame 60!!

try to start playing from frame 1 and it works...


Alternative ways of controlling camera, other functions

Go into Camera View Numpad 0.
Enable Lock Camera to View.
Press N or open the Controls Region (or click on the triangle at the top right of the 3D vieport), in the view tab enable Lock Camera to View.

Then you can naviage like you do with other views or using the numeric pad.
Numpad 4 and Numpad 6 will rotate left right.
Numpad 8 and Numpad 2 will rotate up and down
Numpad + and Numpad - willmove the camera forward and back
For Version 7.9:


Mesh lagging behind another mesh in the same target bone

Okay, found out while accidentally messing around with the object constraint. I noticed the main gear piece was going in front of the armature itself. I set the bone influence to 0 on the object and now its moving with the bone properly.


I'm using v2.71 and I can't find any blend sky option under the world tab

Make sure your using blender internal.

It's under the world panel as per screenshot.


Mirror Modifier not working with subdivision surface

You have to enter Edit Mode (Tab) and then select edge select mode (Ctrl+Tab). Then press N to bring up the Properties panel and set the Mean Crease of the edges along the mirror plane to 1.00.


Overriding Context for bpy.ops.transform.shrink_fatten

@batFINGER's comment is helpful: you (probably) can't override context for edit mode. I ended up just replacing the shrink_fatten operator with the equivalent function, per this:

def execute(self, context):

    ob = bpy.context.object
    me = ob.data
    bm = bmesh.from_edit_mesh(me)

    for v in bm.verts:
        if v.select:
            v.co += v.normal * self.factor

    bmesh.update_edit_mesh(me, True, False)
    return {'FINISHED'}

which was an order of magnitude easier and could be, in general, potentially the best way to replace relatively simple edit operations instead of overriding their context.


Difference between Write Normals and Smooth Groups option in export .obj?

Write Normals does what it says - it write actual normals (face corner ones, i.e. one normal per face and per vertex). This is the most powerful and precise option, since it not only allows support of sharp edges and smooth faces, but also advanced low-poly tricks used in games and architecture, like 'rounded' edges etc.

Smooth Groups are a simplified version to store some non-uniform shading, it defines groups of faces that form a smooth surface. Meaning, edges between faces of a same group are smooth, while edges between faces of different groups are sharp.

Which one to use is mostly a matter of “what is supported by target application(s)”, though I would recommend to try normals first, since they allow more possibilities.


How to do photogrammetry within Blender?

Although quite labor intensive, and far from automatic (but certainly cheap), it would be possible imagine a workflow using tracking information to reconstruct objects based on photographs.

Using a rotatory platform photograph an object. Bring the image sequence into the Movieclip editor and track as many of the object's features as you can.

Solve the scene and setup a tracking scene.

On the 3D viewport enable Motion Tracking.

Instead of your object moving you'll be presented with a camera that moves around a bunch of markers (the tracked points on the image sequence).

Using those markers you'll have some guidelines to reconstruct the geometry of your object.

Or you can select all your trackers and convert them to vertices by using
3D Markers to Mesh.

That will create an object with a point cloud of unconnected vertices. You can then connect the dots...

Once you are done with the modeling, you can use some of the same photos to project the textures onto the UV unwrapped model using the UV project modifier and the camera as projector.


Make a copy
simple answer is `
self.backup[obj.name] = obj.data.copy()

without making a copy you had a reference to the same mesh.  If you are using bpy.ops.mesh.convex_hull suggest instead using bmesh see
Is there any way to make multiple objects convex hulls?
Convex Hull as Mesh
The data is already stored for us in the blend file data,
me = context.object.data

which without any renaming of meshes inbetween is still
bpy.data.objects[me.name]

Hence could simply keep the name, make a new mesh with another name for convex hull and swap using meshes retrieved via names.
If after creating a convex hull mesh and want to have it available permanently An approach to consider would be giving a mesh object a pointer property to the mesh of its convex hull.
bpy.props.Object.convex_hull_mesh = PointerProperty(type=bpy.types.Mesh)

create convex hull mesh and assign it to this property to save it.  Another boolean property could be used as a flag to swap between original and convex hull mesh.


I figured it out with the 3pointedit post.

I had to set the Local Camera option to the proper object(camera in my case).
I used to just change the Scene's camera but apparently do not work anymore. At least I know another way to change it.

[Update]

Here is the button I hitted by mistake :

Now I can change the active camera directly from the scene menu.

Button active : only camera can be selected as camera from the Scene menu.
Button inactive : Camera in Scene menu do nothing, but in the first picture, you can set any object as a camera.


Why are there extra deform bones in rigify armature?

As said, this is to improve your weight painting in case of mesh flipping issues during twist movments.
You can modify the number of limb segments produced by the metarig in Bone Properties > Rigify Type.
For example, if I set the left arm Limb Segments to 1:

The metarig will produce a rig with 2 segments per metarig bone for the right arm and only one for the left:


How can I model an irregular object made from laser cutting metal sheet

You could easily do this with the classic combination Array + Curve modifiers.

Since your metal sheet seems to be cut in a repeating pattern start by defining a mesh shaped as one module of said pattern.
Make use of a Mirror modifier, if it is symmetrical.

Add two Bezier Curve objects to your scene, one defining the larger radius of the desired shape, the other defining the shorter radius and the section of the torus like object.

Make sure the smaller curve is set to 2D in the Properties Window so it doesn't accidentally create gaps. Also make sure both curves are at the same scene position and world coordinate as the pattern mesh.

It also helps if the curve origin is set at one of the end vertex for the section.

Now to the pattern mesh add one Array modifier set to Fit Curve, and pick the smaller "section" curve. Then add Curve modifier pick the same Bezier object.

Adjust spacing and rotations as necessary if the deformation is unexpected.

Repeat the above steps of Array + Curve for the larger curve.

Now adjust the shape and deformations of the mesh by entering Edit Mode in either of the curves and playing around with its shape. Move vertex around or alter their Radius property for a scaling or collapsing effect.

Disclaimer: The gaping deformations that naturally happen by stretching a metal mesh won't be recreated using this technique, but you can manually model them while defining your base pattern object, or apply the modifiers and sculpt them over (a copy of) the final mesh if you don't need a non destructive workflow.

Also see related How to model braided nylon sleeve