text:
Adding 'stretch to' constraint on spring with target will change direction of spring
I am trying to add a spring to my object's armature that will stretch and shrink. But when I apply the 'stretch to' constraint in the 'Apply constraint (with targets)' section, the spring suddenly changes the direction and is not aligned with its target (shown in pictures below). Could anyone fill me in on what I missed to have the spring align with the target?

I have been following this tutorial (spring part starts at 8:52) https://www.youtube.com/watch?v=ttNMGQLuz_w
and it seems that he manages to align the spring with the target, but I don't understand how he does it cause he doesn't explain the specific steps to align the object.

did you apply the rotation and scale in object mode (CTRL + A)?

No. But I did try it and its still not working. Could you tell me when and how I should apply rotation and scale?

To fix this you have to Select your Spring and press CtrlShiftC to add Constraints (with Targets) and choose "Copy Transforms" Constraint, this will add an empty were your mesh is and copy its Transforms this way giving your mesh the default: location / scale / rotation and for you to be able to change it, by moving / scaling / rotating your empty


text:
Objects aren't visible when I render the image
I asked this question earlier without too much context. I attached the file of my blender project to provide better info. Here is what I wrote in in my previous thread:
So when I render the lamp most of the meshes don't show up. All objects are set to be rendered so I don't know why this is happening. Also when I copy the lamp and paste it in a new blender window, the same objects that won't show up when rendered in the original file won't show up in object or edit mode.
I attached the file on the following link:
https://drive.google.com/file/d/0Bw9YfCDmAT5BNGVGOU1aRnRKclU/view?usp=sharing

I deleted the original post.

@Midnightkimchiramen For future reference, it's preferred to provide clarifications and additional information by editing the original post.

could you add a screenshot of your rendered image?

LAYERS

Do the following for every object from largest object to the smallest.  In the object panel / Relations click on layer (1) so it is dark as in the image above, the upper left layer rectangle of 20 possible.  Then click render.
These layers are coordinated with these Render Layer Settings

When a new simple file is created objects are on layer 1 and the render layer settings are showing at least layer 1.  Blender gives the user the flexibility to hide or show these layers at different times and phases.  It can be used as a feature or to create confusion.
If you want to know more you can now search at this website and blender.org and video site for information about [layers].  Quick Summary.  Every file can have multiple render layers.  Every render layer can select some of the twenty layers.  Every object can be on some render layers.  All 3 concepts must be coordinated with other hidden delights for an object to appear in the render.

I don't have an answer; I would comment if I could, but I'm a n00b here and I don't have reputation points. But I wanted to throw in what I found.
I was playing around with joining and separating everything in the scene, and this monster appeared. I'm getting it to appear by selecting everything in the scene and joining. You might have to join/separate on repeat.

It breaks down into these parts, many of which seem redundant:

Have you seen this thing before? In edit mode, nothing shows as selected, though it behaves as if it is when I manipulate it. And once it appears, the verts count goes to 0.
I also noticed that the spring pieces disappear when they're joined.
If it's any solace, I'm thoroughly confused.

I am confused as to what you have done in the images. And I tried joining/separating although maybe my approach towards the process didn't change anything; I joined and separated each object by twos and I'm sure thats not the way to do it. Also, when in edit mode, individual objects do show as selected so I know as much as you do in this confusion. I did also notice that the springs disappeared when I joined them with their adjacent objects. I might as well try remodeling again.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


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Blender does not play audio track after restart
I try to use Blender as a video editor.
I dropped 1 video, 1 mp3 and everything was ok - video plays, audio plays.
As soon as I restart Blender and go to last session video track is ok, but audio track has no sound.  Rendering also will have no sound.
What is it?
PS: if I render just after I dropped mp3 - there is sound in rendered video (as it is in preview window).

Check you haven't accidentally muted the strip, and try "update animation cache" in properties > scene > audio.

This was only when I pressed to recover last session.
If I open .blend file - everything was fine.
I noticed Blender was trying to open some file in /tmp dir. And it couldn't.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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geometry nodes : sticky mesh?
there is a nice sticky mesh experiment made by Alex Martinelli on twitter (check the video).
Any tips on how building something similar ?

Thanks !

To me it looks like he is moving two spheres here, and moving their points with transfer attributes to the nearest point of the other mesh. After that, he just randomly distributes points (volumes?) on the surface. Just a guess. Try it.

A few days ago I saw something similar here (tutorial about sticky vines)

As mentioned in the comment, it looks to me as if a sphere is simply moved and its points are aligned to the nearest object.
However, to create the desired effect, a volume is apparently used here.

There are, of course, several ways to create this, but to me, turning the mesh into curves, and those curves into points, seemed the most obvious solution.
Of course you could also create the points on the surface with Distribute Points on Faces, but I think that in this example directly the edges were converted to points.
In any case, the following example could be a solution for you, with which you could approach the desired result step by step:

(Blender 3.2+)

That is sick.  Thanks !

So your initial cube isn't used there.  Why do you start with an Ico sphere, and why does it needs to be converted to curves ?  Thanks !

@gordie You are welcome! And yes, that's correct: The geometry in this setup is created exclusively with Geometry Nodes, and the cube no longer plays any role at all here.

@gordie You can of course use any shape for it instead of the Ico Sphere. For me, it just looked in your example as if a sphere would be used here. The node Mesh to Curve is also not mandatory here. It was the closest I could get to the example you showed, because it creates the points for the volume along the edges, rather than at random positions on the surface. It takes a bit of trial and error here, and it just depends on what exactly you want your result to look like. But the technique itself is a good starting point, I think.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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how can I get the radius of a curve circle from the Object Info?
Is it possible to catch the radius of a curve circle in Geometry Nodes,
from the "Object Info" node ?
I've seen there is an Input > Radius node, but I need to get that data outside the curve circle itself.
Thanks !

you can use this node setup:

result:

ok, sorry, you have to divide it by 2....but i think you can do that ;)

I think they meant the radius attribute that's tied to each control point

ah...ok....i think you are right

ok...he checked as ok...so i think you are wrong :D

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Assets Browser makes my file twice bigger
I'm just testing the new Assets Library feature of Blender 3.0.
Just for the question :
I had an old file (26Mb) that had 280 low-poly humans in a collection.
I marked them all as assets, and cleared the scene.
So now I have an empty file, with my 280 low-poly humans in the Assets Browser.
But the file got bigger : 44Mb, which is almost twice bigger.
Does anyone knows why ?
Thanks

The file size increase comes from the asset metadata.
Which upon very empirical testing takes about 64 ko of space on disk per asset.
$64 * 280 = 17 920 ko $
$17920 + 26000 = 43920 ko = 44 Mb $ (roughly)


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geometry nodes: how can I remove a list of points (using their indices) from a selection?
I have points generated on a grid.
I would like to arbitrary exclude some points (using their indices) from the point cloud.
For example, let's say I want to change their radius.

Is it possible to make calculations (join, exclude, intersect, etc...) on Geometry Nodes selections ?
Thanks !

I suggest you read some material on the subject of boolean operations or boolean maths

You are looking for a cascading or.  You'll need 3 or Boolean nodes:

but you can't use the Boolean equal nodes.  You have to use the Math Compare node instead.  The Boolean equal node is trying to compare two Boolean values but you want to compare two integers.
So you need to change the four nodes on the left:

You'll also want a Boolean not between the last or and the Set node; since you want everything but the specific nodes:

Note: I used a Set Position node, but this group works fine with the Set Point radius

The task of making logical selections from a grid comes up quite a lot, and while it can be done case-by-case, it can get very repetitive. An 'Indexed Grid' group might make sense.
This group:

Constructs a 1D,(line) a 2D, or a 3D (with internal vertices and edges) grid.
Allows the number of divisions, and dimensions, to be set.
Indexes the vertices by their [division number] in X,Y, and Z, from 0 to Count-1
Returns whether the vertices are in the minimum or maximum planes in X,Y, and Z
Also captures vertex-neighbour counts, which can be quite useful for some selections

It starts by making grid of unit cubes, covered for the edge-cases where the grid is 1 or 2D:

..and then incorporates that into an 'Indexed Grid' group which scales it to dimension, having captured the indices, max/min, and neighbour-counts:

There's nothing too interesting  here, that couldn't be done case-by case, but it does take some of the slog out of doing it every time, and might be easier to play with, making selections, than rebuilding every time.
For instance, to select the corner columns you illustrate, first select all the points which are Max OR Min, by adding, and then find the ones for which that is true for X AND Y, by multiplying, as here, or by using the Boolean Math > AND node

Here are some selections based on the number of neighbours:

.. and the indices can be passed out to shaders:

Select corner points of a grid with only one value (number of rows or columns)?
In any case, you must know (or find out) the number of rows/columns.
With this value you can separate the rows/columns that lie between the first and the last.
Then you need the index sequence of a row (from 0 to $n$ or the first and last point in your row). You do this with the Math Node and the mathematical operator Modulo.
With greater/less than you get the points between the first and last point of all rows.
If you now combine this selection with the previous one and filter out the points that are not present in either of these selections, you will get exactly the vertices of your grid.

And here is another interesting variant:
If you use Ping-Pong and use half the number of points as Scale, you also get useful numbers for a grid with which you only have to compare the number of points of a row:

Wonderful answer, thanks!  I validated the other one because it fits my question better, but your explaination is very interesting.


text:
Is there a way to sculpt (with dyntopo enabled) a textured mesh?
I'm searching a way to sculpt (with dyntopo enabled) a textured mesh.
What I want to do is load an image texture (a portrait) and sculpt it.
Thing is, when I enable dyntopo in sculpt mode, I get this warning and the texture is hidden until I exit the sculpt mode :

I understand the "concept" of this problem (mesh is edited > UVs are changing > image mapping is changing); but I need to be able to do this - I cannot sculpt without seeing my picture.  Of course, I could disable dyntopo, but then I don't have the precision I need.

I've tested using the UV project modifier (does the same)
I've also tested sculpting my mesh in wireframe mode, on a reference image / camera background image : it works, but I don't get the "feeling" of what i'm sculpting.

Is there a way to achieve this ?
A thing that could help would be to have a way to "unsync" modes between two viewport panes (one would be in sculpt mode, the other would be locked in object mode).  But I don't know if this exists.
Any ideas to help me on this ?
Thanks !

When you use the Generated or Object output of the Texture Coordinate node, you can use Dyntopo in Sculpt Mode. The question is if this mapping suits your needs and how usable it will be after you've begun sculpting. So this may be not the best answer.

that is aweSOME!


text:
Using Blender as a video editor can I only add an audio track without recoding a video track?
The task is to add an additional audio track to a video file (mkv).
But I do not want to change a video track in any way while rendering.
Can it be done in Blender?

AFAIK no. This isn't something blender is designed to do. You might try using avidemux, or if that doesn't work for you, maybe try asking on video.se

No, it can't.
Blender only sends its render output to ffmpeg internally which means it's being encoded (again when using decoded footage in the VSE). You can use Blender as a Frameserver as well, but that won't help you out either.
Instead you should use Avidemux or mkvtoolnix to accomplish your goal.

Edit: As pointed out by Troy James Sobotka in the comment below, using FFMPEG directly would be a solution:
ffmpeg -i video.avi -i audio.mp3 -codec copy -shortest output.avi

While absolutely correct, I'd add FFMPEG to your list of solutions. ffmpeg -i video.avi -i audio.mp3 -codec copy -shortest output.avi. See http://stackoverflow.com/a/11783474


text:
How do you import an object from another Blender file without losing textures?
I built an LP Record in another Blender project (including colors, textures, images, materials) and tried to bring it in to my current Diamond Head project:
I appended the Diamond Head project with the LP object. I got the disc shape rendered in gray. So I tried importing the Materials and Nodes to no avail.

My objective is to have the record spinning in the crater, so I need to merge the two projects. What's the best way, if any, to accomplish this?

Use a consistent set of materials for a Render engine.  Cycles Render or Blender Render.   Do not mix Cycles and Blender materials.
It appears you have tried to mix materials for the two different render engines.
If you are producing a single still photo you may be able to render one image as transparent .png file.  You may be able to render the album disc as a texture and apply it as .png which is render engine neutral.

I agree with atomicbezierslinger that your problem is that you tried to combine two different material protocols, the Blender Internal render for the landscape, and the Cycles render for the vinyl disk. But if you want to merge the two, what I'd do is to take an image of the disk by placing the a camera perpendicular to the plane of the disk, and take a screenshot, saving it in a suitable format (e.g., uncompressed, single-layer tga). Then I would take that image, and use the image to place an image texture on the disk you imported into your Blender Internal project.


text:
Why does my terrain warp when I unwrap?
I used many areas of Google terrain from Sketch Up and joined them together in Cycles.  then I stitched them together and removed doubles.  As you can see, when I unwrap it's warped.  I'm a newbee, be gentle :-)

Btw. Where (geographically) is this (the terrain) from?

Switch to top view, then in edit mode select all the mesh, hit U button to unwrap and from the menu select Project from View (Bounds)


text:
Game Engine lags when activating sound with keyboard
I have a basic character set up in an FPS style game I am building. When the player presses W to move forward, I want the game engine to play a walking sound. However, when I link the W keyboard sensor to the sound actuator, anytime I press W in game there is a spike for Logic on the profiler and the game lags a couple milliseconds. My audio file is an mp3, but it does this with WAVs as well. Thoughts?

From what it seems to me, you have a Keyboard Sensor stringed to a And Controller stringed to a Sound Actuator.  When in this setup the game will always lag for this reason: when a keyboard key is held, it sends many pulses per second to the computer to act as input.  If you have something like a Motion Actuator, then this isn't a problem, as it just makes it move forward continuously.  However, with your Sound Actuator, what it's trying to do instead is to start playing the sound file every time it receives a pulse (which by default is 60 times per second).  So in effect every frame the key is held it tries to play the sound, which is more than the game engine can handle, and as such it slows down.
Now, a setup that doesn't have the sound playing 60 times at once is as follows
[WARNING: TECHNICAL JARGON AHEAD!]:
First delete the malfunctioning sound actuator part you set up.
Use a different Keyboard Sensor than the one controlling the movement of your character,  but assign it the same key (W).  Click the ''' icon on the sensor to darken it, then in the frequency box, enter in a number other than zero (the basis of this number is how many frames is in between pulses, for example if you put in 29, then there will be 29 pulse-lengths between every pulse sent to the computer, making the sensor do 2 per second at 60 frames per second.  The larger the number the more time in between pulses.)  See this page on Sensor Common Options for a little more of an in-depth look on this function.
Then add your And Controller and a Sound Actuator set to use your sound.  If everything goes correctly, you should have some evenly-spaced footstep sounds with no lag.
If this was good, consider upvoting! :)

Personally, I don't see the word "buffering" mentioned at all in your post.


text:
is the full image always computed when rendering a single pass?
I've started learning the compositor.

I need only the glossy pass for now.
But I see that, when I render my image, the "full" image is rendered, then the GlossDir layer.
I was wondering if there was a way to render the GlossDir pass directly without having the need to render the image first.
Secondly, even if I've checked the denoiser in the render tab, my GlossDir pass is not denoised (so I added a Denoise node).  Is that logical ?
Thanks !

If I am not mistaking, the passes are what compose the final image. The render engine isn't rendering "the full image" and then "the individual passes", instead it renders all the passes and then exposes the final result (what some other softwares call the "beauty pass") and the passes you asked to see individually. Sort of similarly to when you ask to see the individual channels of a picture.
As for denoising, the one you find directly in the render settings is only applied to the final image, not the individual passes. My guess is because most of the time, it's more efficient to denoise one pass that X amount of passes, and people who want to denoise passes can do it in the compositor like you did.

This makes sense..  thanks for the explanation..


text:
how to display point index next to the point?
for debug purposes,
I'm trying to display indices as a text field next to my points.
But I don't understand how to catch every point index value.

Could someone help ?

Thanks !

Building on Chris' answer, here's a way to display numbers larger than 9! I built a node group called "Label points", which takes a Geometry, an field based on the points, and a font size. It works by creating the "tens digit" separately, and shifting them to the correct position:

It can be used like this:

Resulting in an output like this:

This is NOT a complete solution, but a path to the solution ;)
with this node tree, you can show the indices from 0-9

to make it work for more numbers > 9 you have to combine the right numbers. So that's more math than really geometry nodes.

for really good help you could study his work here:
https://artofriaz3d.gumroad.com/l/indexviewerfields

Thanks for the tip with the index viewer! ;-)

you are welcome! Meanwhile a build even my own index viewer ;)

This was very helpful. I would like to suggest adding just two nodes to blinry's setup. If you look at the furthest left point of his outer star you'll notice that should say 10, instead it says 0. Also the furthest right point on the outer star starts at 0.
You want to add a math node after the instance index to make the first index display the number one. This is passed directly to the standalone instance on points node to shift the string value up one place.
and you also need to add another +1 math node inside the node group going into only the tens digit section divide node.

Awesome native way to display the index of a selected vertex, as seen in this video:

turn on Developper Extras in Edit > Preferences > Interface.
Then in the Viewport Overlays, in edit mode, turn on indices (available for meshes, not for curves!)
Done!

This works only in Edit mode and displays the vertices before the geonodes modifier is evaluated.


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UV Project modifier : is there a way to combine two UV maps in a same material?
I have an object that has a material (which uses textures).
I want to add a graffiti on it, so I plugged an Add Shader node to include my graffiti texture in the material.
Then, I use an UV Project modifier so I can "project" the graffiti where I want on that rock.
But this messes up the original textures of the object, since, I guess, the UVs are redefined by the UV Project modifier.
Is there a way to combine two UV maps in a same material ?

you don't need a modifier, you can create a second UV, then use it in an (Input) UV Map node

You can create a second UV map:

Then select this second UV in a (Input) UV Map node, and mix the 2 Image Texture through a Mix Shader for example (use the Alpha output of your image as factor):


text:
Geometry Nodes : how can I delete a single spline in a curve object?
I thought it would be easy to delete a spline given its index in a curve object, but it's not :)
I'm on Blender 4.3 and this is what I have so far - i'm trying to delete the spline with index "2".

It does nothing.
If I change the B value to 0, every spline is deleted.
What don't I get ?

Works fine on my end.
You are supposed to use the Index from Geometry > Read > Index node.
The Socket Spline Parameter > Index will give you the index of a control point at each spline.

This index is the index of the point on the current spline. If you have multiple curves in the object, then the point index go up along the curve, then restart from 0 for the next curve, and so on.
From the manual about Spline Parameter > Index :

Each control point’s index on its spline. This is different from the output of the index node, which also counts the control points in all previous splines.

You can use the Curve Info > Curve Index instead. You'll get the index of the splines as you are expecting.
Another solution is presented by Duarte Farrajota Ramos. I'd say his answer is cleaner and simpler.

Curve Info: Curve Index you would use if for some reason you were deleting points (for example you want to delete both one entire spline and also some point(s) on other splines in one go).


text:
Geometry Nodes: can I animate (trim) a curve in real time at the moment I'm drawing it?
in the asset from Blender Studio, 2D Smoke Simulation Setup
smoke is animated in real time each time a new spline in drawn.

How could I reproduce that ?  I would like to animate a spline (trim) each time it has been drawned.
Thanks !

When you render something, Blender doesn't take previous frame to modify it slightly. It generates a new frame from scratch (OK, rarely some very limited data is cached and reused). So the question is hard to understand, it would be harder to, for some reason, reuse the spline. \

There is a downloadable blend file in the link you indicated in the question. All is there.


text:
How can I make light particles (like feathers) explode then fall down slowly?
i'm trying to make an animation where a characters head appears suddently in a pile of hay.
The straw particles should almost explode on the top of the pile, then gently fall down.

I've tested using physics (among others with this tutorial, wind on leaves), but cannot find a way to make it look good.
I also tested with a cloth (straws would be a texture on this cloth) pushed from below by a ball, but it doesn't look right either.

I've found something that approaches what I want (pillow hitting the ground), but this is just a video, there is no explanations.

Any ideas of how I should handle this ?
Thanks!

You can create your emitter, your particle, and put a Force Field > Wind and a Turbulence underneath:

In the Particle panel, under Velocity > Normal increase the value up to 10 for example to give a bit of dynamic to the particles (if they need to go up instead of everywhere, push up the Object Align Z value). Select the Wind and in the Physics panel, create 2 keyframes on the Strength, for example 0 at frame 10, and 8 at frame 20. Give your Turbulence a Stregth of 20. When the action begins, the particles explode due to their velocity, then they are slowed down by the Wind, and agitated by the Turbulence:

I tried a simulation without adding Vortexes etc if you have a slow Computer.

The result should look like this:


text:
Geometry Nodes : capture the "Start & End Mapping" factors values from a curve object
I'm working on an animation with curves, using curve trimming.
I do my animation drafts using the Start & End Mapping factors for the curve object, but in the end I would like to use Geometry Nodes and the Trim Curve Node (because I want also to add other effects in the process).
Rather than animating all the stuff twice (both using the Start & End Mapping factors, and the Trim Curve node), is it possible to retrieve the values of the Start & End Mapping within Geometry Nodes ?
Thanks !

Can we ask why you're not using Geometry Nodes from the get-go? Is it quicker, in your case, to use the Mapping-Factors?

I use the mapping factors as a "draft" before starting to use GN.

Okydoky, just curious... since GN is a modifier, I would have thought it offered non-destructive drafting in its own right. A simple ' Trim (fac_start, fac_end) ' group, copied between curves... (which could also stash fac_start, fac_end on the geometry, if needed)


text:
How can I use a boolean to substract a part of a bezier curve?
I need to substract a part of a bezier curve with a boolean object.
Since I need to animate the part being removed, this needs to be dynamic.
There is no boolean modifier on curves,
and I’ve tested with Geometry Nodes (curve to mesh > mesh boolean) without managing to achieve it.
Does anyone knows how to do that ?

Do you also want to animate the curve?

Would you mind telling us how you tried it with Geometry Nodes? Because for me it works quite easy. You know you have to plug a Profile Curve into the Curve to Mesh node to get a mesh that works with Mesh Boolean?

Could you illustrate the desired result... what this Boolean is for? Alternatives might depend on that.  (Is the subtraction in the middle, at the ends, out of the side of a bevel... etc.etc.)

A node set up like this allows me to Boolean difference a curve. Be sure that your Bezier curve has no bevel in object data properties. Otherwise, the geometry input would be a mesh and the Curve to Mesh node wouldn't work. Giving the curve depth has to be done in geometry nodes in this case. I used a Curve Circle.

If you have a Bevel Depth on the curve it works, too. Then you can simply skip this whole Curve to Mesh part and plug the Group Input > Geometry directly into the Mesh Boolean.

@GordonBrinkmann Yup, just make sure "Fill Caps" is enabled in the curve data, and to add a "Merge By distance" node before the boolean to prevent weird behaviour the default curve caps are not merged to the curve body

@GordonBrinkmann Oh I see, do you know if I should correct this answer or leave as is?

@Gorgious You can do that if you want filled caps... but it is not necessary to make the Mesh Boolean work.

@AdamSwearingen Well, your answer is not incorrect. The node setup works, the other option is just a different way to do it. And the Mesh Boolean in your setup even works if you have a Bevel Depth, then the Curve to Mesh just throws an error, will be ignored and instead the Mesh Boolean uses the mesh from the Bevel Depth.

In fact, I've noticed that it seems to work, but that it depends on the origins and scale of the objects : I've got my mesh substracted, but at the wrong place.  Any idea on how to achieve this in "relative" mode ?  See capture here


text:
bone constraint : I don't understand how to "copy rotation" correctly
I'm trying to copy the rotation of the target bone of a leg chain to the foot, like in this tutorial.

Thing is, Blender has changed and the constraint has not the same options than before.
I don't understand which settings I should use to have my feet following the IK target rotation correctly.

I managed to have a rotation constraint, but the rotations go in the wrong directions.
Also, the offset mode (as used in the tutorial) is labeled "legacy" in Blender 3.3.0, so maybe I should use different settings.
I'm quite new to armatures.  Maybe I'm doing something wrong.  Guess this is related to the bones orientations.
I also did a Recalculate Roll Global +Y axis, I don't know if I needed to.
Could someone explain what's going wrong and how I could fix it ?  I don't just want to fix it, I want to understand it.

The video's "offset" is, yes, the same as setting the Mix mode to "Offset (Legacy)".
This wasn't ever a good way to do it, even when the video was made.  Offset world space rotation isn't what you want; it wasn't a well-considered way to mix rotations in the first place, which is why it's now considered legacy.  It exists only to support older files.  The video, in my opinion, offers poor advice.
However, the modes that have been made to replace Offset are, still, not necessarily well-considered.  There is no simple, single mode change that will make the Copy Rotation work as you want.
Instead, to make it work properly, we can add mechanism bones, that exist only to make our constraints work properly, not intended to deform the mesh or to be manipulated as controls.
Start by duplicating your feet bone, then parent these bones to your IK targets.  Parent these duplicates to the appropriate IK target.  Disable "deform" property on these new bones, in properties/bone/deform.  It's not necessary, but I'm going to also name and scale these duplicates down, so that we can easily see which is the deforming foot bone and which is the duplicate:

Now we'll enter pose mode.  Delete the constraints from these duplicates.  Change the copy rotation constraint on your foot bones to target these duplicates, on world->world, with "replace" mode:

Because the new bones are duplicates of the constrained bones, their axes point in the exact same directions as the constrained bones at rest; as we rotate their parent, the foot bone follows that rotation perfectly, regardless of the parent's axes.
Note that Moonboot's suggestion to parent the foot to the IK is a valid alternative (if you then follow it with a copy location constraint targeting the tail of calf), it does the exact same thing barring bone scaling, but I didn't demonstrate that because you specifically asked about copy rotation.

Choose Target and Owner > Local Space, or maybe simply parent the foot to the controller?


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Is it possible to dynamically inset a mesh (using a modifier)?
I would like to know if there is a way to dynamically (with modifiers) inset a mesh.
Thanks !

Is the double ring the same mesh as the rest or are these 2 objects ? The smooth modifier might help here


text:
is there a way to relocate a linked collection that has its name changed?
I know there is a way to relocate a broken file in the outliner,
But is there a simple way to relocate a collection when it has its name changed ? (file is the same but the collection has a different name)

Thanks


text:
NLA : is it possible to "hold backward" an action strip?
I know about the Hold Forward extrapolation mode of an action strip in the NLA, which allows you to to extend the pose of the action strip.
But is there a way to "hold Backward" ?
I mean, I would like that my pose starts sooner but without changing the timing of my action.
Thanks !

Have you tried the "Hold" Extrapolation Mode? This allows you to hold the first frame and the last Frame of an action strip. This works in both ways. Or do you want it only "Backwards"?

In case someone comes looking for this. When I need to implement "Hold Backwards only", I set extrapolation to "Hold" and add a non-zero blend-out. With a non-zero blend-out, hold forward is effectively negated.


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playing with View Layers - are they always all rendered?
I'm playing with View Layers since I have to separate a lot of stuff from a scene.
It's working great but I was wondering how it does impact the render performances.
If I have, let's say, 10 View Layers; but only one is used in the compositor.  Are they all rendered or just the one that is used ?
Thanks.

Yes, one by one. Each view layer has a "Use for Rendering" property -> View Layer Properties (image stack icon) > View Layer > Use for Rendering. Disable that if you want to exclude one view layer from the actual rendering.


text:
rendering a (glass) bottle with a liquid in it
I'm trying to render a soja bottle (transparent) with glass in it; but when rendering it (Cycles), it looks weird - like if the liquid was cut in bias :

My mesh looks okay.
I have a bottle that has a solidify modifier, which has a basic BSDF glass shader with a 1.53 IOR.
The liquid is another instance of the bottle, which has a boolean modifier and a displace modifier (to "inset" it).

I don't know if this is the right way to achieve this.
Since the bottle is two-sided (out and in sides); maybe the refraction is computed twice ?
Is this a correct way to render a bottle with a liquid in it, or is there some tips I should know ?
File is here if you want to have a look.
Thanks !

Related: fluid in a glass

@brockmann ... in this case, though, since soy sauce is nearly opaque, you could probably get away with the surface of the liquid being between the inner and outer surfaces of the glass, not bothering with the IOR calculations on the common surface? Not physically accurate, but....

I haven't fixed it.. (may pop in an answer if I have time to play with this) .. but the dark area is the reflection of the background beyond the end of the floor of your cove.

i don't know what you want to achieve with your displace modifier in liquid, but if you disable this in viewport, you got this: [1]: https://i.sstatic.net/t4z7E.jpg

@Chris The displace is to "shrink" the liquid (which is the same mesh than the bottle) inside the bottle.

@RobinBetts Absolutely right, just thought might be nice to link this one in case since gandalf's explanation is sweet.


text:
Blender closes when rendering
I just started learning blender and I have a problem when rendering my model. Sometimes when I change my viewport shading to rendered my Blender closes.
Here is my settings:
Cycles render
Device: GPU Compute
And I also set my system preference to Open CL > Tahiti
My computer specs:
CPU - AMD FX-6300
GPU - R9 280X
But when I rendered it using CPU it does work properly. Sometimes it also works using GPU, I don't really know what's the problem.

sounds very much like a memory issue. How much memory does you graphics card have, and do you know how much gets used when you render something?

OpenCL rendering with Cycles is relatively young in Blender and largely experimental at this point. It is still feature limited, unstable, and prone to crashing as it currently stands.
Can you provide a blend file that crashes?
Try upgrading your graphics drivers, restarting and see if the situation improves. Otherwise it is probably a bug and should be reported in the bugtracker.


text:
Where should Blender Download to?
I am pretty new. About a month into this. Still learning so please excuse the noob question. I uninstalled it after my first animation. I thought it may be the reason for my Java problems. Not sure about that but that is fixed and I am back. I noticed this time when I installed it that it went into C://Program Files/Canon/Easy-WebPrint EX. That's my printer files. Is that normal? Do I move it out of there? Maybe that was the problem the first time. idk

no that is not the normal directory. If blender is working, then no you dont need to move it. I would recommend the zip just unzip, put it anywhere and run blender, no install required.

You may be confusing download location with installation location, both are completely different and unrelated.
If your file downloaded to that printer folder is because you chose to save it there, or through inaction (you didn't select a proper folder and just pressed Ok) let the browser save it there. Depending on your browser, that folder may have been the last used to save the last download so the next time you used it defaulted to the last used directory.
After download you must unpack (for ZIP files) or install for (MSI files). Where you install this from is irrelevant, what matters is the folder you now install it to. The MSI file should by default install to the correct location wherever you run it from, whereas the ZIP file will be extracted to where you tell it to, if you just right click it and coose Extract it will stay right in that weird printer folder you mentioned so it may seem like non standard location.
Either way non of that should cause any trouble for Blender or Java, Blender doesn't use or interfere with Java and the folder you run it should be mostly irrelevant.

I would think it installs to where you choose to install it. But you can also download the zip-file and run that directly, without installing anything. So Blender would not cause Java-problems.


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Playing Animation before Rendering neccessary?
Do I have to play my animation from beginning to end (starting at frame 0)before rendering it?
Because if I do not the simulation I use (cloth) doesn't work.

Yes, you must. Simulation and animation is not the same. You must bake simulations before rendering. I highly recommnend using bake button in simulation properties instead play animation button in timeline.


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Failing to compile blender 2.80 - help needed
I am trying to compile blender 2.80 so that I can later compile the sphinx docs for the updated python API.
My ultimate goal, is accessing the new API docs.
But it would be great to understand why I keep failing to compile blender.
I made a docker image specifically for compiling blender, I followed the official build instructions, and I do install all the dependencies.
This is my work so far, it can take about ~2-3 hours to install all the dependencies and compile.
https://github.com/egidijus/blender-compile
The error I receive while compiling is:
-- Found OpenImageIO: /opt/lib/oiio/lib/libOpenImageIO.so
-- Found OpenColorIO: /opt/lib/ocio/lib/static/libOpenColorIO.a;/opt/lib/ocio/lib/libyaml-cpp.a;/opt/lib/ocio/lib/libtinyxml.a
-- Could NOT find LLVM (missing: LLVM_LIBRARY)
-- LLVM not found
-- Found OpenSubdiv: /opt/lib/osd/lib/libosdGPU.so;/opt/lib/osd/lib/libosdCPU.so
-- Found OpenMP_C: -fopenmp (found version "4.5")
-- Found OpenMP_CXX: -fopenmp (found version "4.5")
-- Found OpenMP: TRUE (found version "4.5")
CMake Error at CMakeLists.txt:909 (message):
  Cycles OSL requires WITH_LLVM, the library may not have been found.
  Configure LLVM or disable WITH_CYCLES_OSL

-- Configuring incomplete, errors occurred!
See also "//build_linux_full/CMakeFiles/CMakeOutput.log".
See also "//build_linux_full/CMakeFiles/CMakeError.log".
make: *** [all] Error 1
GNUmakefile:268: recipe for target 'all' failed
ERROR: Service 'blender' failed to build: The command '/bin/sh -c make full' returned a non-zero code: 2
make: *** [Makefile:11: build] Error 1

I would appreciate any help!
Thanks!

for questions regarding building Blender, it's better to ask that at the devtalk forum. There is a solution provided to the LLVM issue you mention provided here: https://devtalk.blender.org/t/i-had-to-reinstall-ubuntu-again-and-i-cant-get-my-blender-2-8-to-build-properly-again/3969/3

Thanks aliasguru, let me try and update the question.

Questions about developing Blender in  C/C++/C# are off topic on Blender Stack Exchange, I believe that would include building Blender. Devtalk forums is a lot better place for this, you are more likely to get better help there.

I'm voting to close this question as off-topic because it is about building Blender and building is part of developing Blender in C/C++/C# which is off topic on Blender Stack Exchange. (See: What questions should be definitely off-topic? )

Further to link posted by @aliasguru I find cmake-gui a handy tool for configuring blenders cmake. Put in advanced mode shows all the settings. Has folder / file select box to manually set those not found by configure.

I managed to compile, but I am unhappy with the outcome, because I have not included all the appropriate CMAKE instructions, and so it explodes when I try to compile python docs....
I will carry on trying to make a predictable blender builder.


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Perform ops class from console
When loading any file, the sun_position add-on/plug-in, although enabled in User Preferences, is disabled in its panel. When trying to dynamically render a scene, using a python file:
blender -b blenderfile.blend -P pythonfile.py -o //outputfile_ -E CYCLES -F PNG -x 1 -f 1

the sun_position plugin is not enabled.
I've tried to invoke the function bpy.ops.world.sunpos_controller() from pythonfile.py, but to no avail. I've also tried to change the sun_position configuration files to be enabled by default, but I couldn't manage to get that to work either.
Does anyone have an idea on how to render a scene from a terminal with sun_position enabled?

Have you tried adding --addons? You can use this followed by a comma separated list of addons. Use in place of your Python script.

@ShadyPuck Doesn't seem to do anything. I'm pretty sure the sun_position add-on is enabled within Blender's settings, just not on the module itself.


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armature to unfold a chinese food box to a flat page
I'm working on an animation and I'm trying to build an armature to unfold a chinese food box like this one; to a flat paper page:

Once flat, it should look like this :

But I've got hard times to make the armature work.
It's no problem to have the main faces working; but I don't know how to handle the paper "folds" in the corners...
I've already tested by assigning manually several times and in different ways the vertexes weights; but I don't get any convincing results.

How would you do / can someone help ?  Here's my actual file.
Thanks !

Unfortunately, the best I've come up with adds two more bones to each of the four corners and requires manually animating at least two of the corners.  Have you looked into doing in the opposite direction with an add-on like orgamify or even just doing it with a series of shape keys?

You have only 1 bone for each corner. Why not use 2 bones so each can control a "face area" as seen in the 2nd reference image?
Frame 1 - Areas of influence of the bones
Then add a keyframe for the rotation of the bones at frame 25 and bring them on roughly the same height as the sides of the box. But let it bend a bit because the cardboard material can not compact:
Frame 25
Then edit the end frame (50) and fold in the two paper folds as shown in the reference illustration. Try to bring the bones in position by rotating them around the X and Z-axis. Then rotate them around the Y-axis to create the folds and if the mesh intersects or is twisted:
Frame 50
Blender will calculate the frames in between, but the animation might not look right. For example, intersections can occur at short notice. So you need to adjust the bone rotation at frame 35 a little bit and get them to a good place:
Frame 35
Animation (50 frames):


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simulate the displace modifier on a curve using Geometry Nodes
There is no displace modifier for curves in Blender.
Would it be possible to simulate it using Geometry Nodes ?
My goal is to be able to softly randomize the position of the vertexes of my curves.
Thanks !

Yes, this is possible by using a texture node and moving the points with Set Position.

The only problem is At the output of the Geometry Nodes modifier you can also output the curve, but this curve is only available as long as you do not try to make it available as a editable curve by applying the modifier.
See Can I create Bezier curves with Geometry Nodes?.


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Geometry Nodes : handle each spline individually
using Geometry Nodes on a curve object, is it possible to handle each spline separately ?
For instance, I would like to compute some stuff depending on each spline's length.
But the Curve Length Node outputs the length of all splines added together.
How could I use a node setup per spline (within the same curve object) ?
Thanks !

What about the Spline Length node?

Does this answer your question? Trim by length in geometry nodes

The Spline Parameter node has a Length field that may help.

Spline length and Spline parameter nodes operate on the complete spline, not its individual elements. I'm searching for the answer too :-(


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Geometry nodes: Alter the radius of a curve to make it look like a worm (by repeating a pattern)
I made a basic "tube" from a curve, using Geometry Nodes.

and I would like to alter the curve radius to make it look like a worm that has segments:

I guess I should draw a "pattern" that should be repeated along the curve, eg. with a Float Curve Node.

How could I achieve that ?  Here's my actual blend.
Thanks a lot !

use this node setup:

to get this:

An adjustment to your method might be as follows:

.. mapping the (0-1) Spline Parameter range to  N (0-1) segments, to make them suitable for the Float Curve node, and further adjusting its output to give a base radius, and scale the Float Curve's contribution, on top of that.


text:
How can I catch an attribute defined in the Group Output node in another Geometry Nodes object?
I've set a "length" attribute in the Group Output node of my Geometry Nodes object:

Now, in a new Geometry Nodes object, how can I "get" that Length attribute ?  I thought it would be available from the Object Info node, but it isn't.
Thanks !

I think you want to save a single data, not the field. But anyway, the only way to save data is to store it into some attribute.

If the data is singular, you can get the singular value using attribute static node

Everything is called value, not easy to understand :) But I almost got it unless this: how can I pass the output attribute variable from the first GN to the input attribute of the second GN ? https://imgur.com/a/NFbTszG

Click on the button on left side of the field

actually if the data is singular, it is better to use the "Sample Index"-node instead of the "Attribute Statistics"-node, cause it doesn't performs any calculations on the whole domain (which can be very large) ...

In the first GN modifier, push the output data into an Attribute. Then in the second GN modifier, access that Attribute as an input:

In Object Data Properties/Attributes, create an attribute to store your data. Choose the right Domain and Data Type. I'm using a Boolean on Points to test the principle.

In your first GN, connect your data to the Group Output node (as you have done). Check the Type and Domain in the flyout.

In that first GN modifier you will have a new Output Attribute. Select your attribute store (from item 1) to route the output data into that attribute store.

In the second GN, connect from the Group Input to whatever node is going to use the data. I'm using my boolean to select which points to place an instance on.

In the second GN modifier, you will now have an Input Attribute slot. Press the button (spreadsheet icon) to switch from a single input to a field input. Select your attribute to route the data into the modifier.

I used the Viewer in each of my node layouts to see that the data was being transferred through. And here is my finished object, showing the starting cube with little cube instances on points 4 to 7:

Thanks for the reply. The "attributes" tab is only available for Meshes, not curves ?

Yes. It looks like Attributes are a Mesh thing: https://docs.blender.org/manual/en/latest/modeling/meshes/properties/object_data.html#attributes. However, as a workaround, you could pass data values from one GN modifier to another using the Curve Tilt or Curve Radius, if you are not using those for other purposes?


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A Problem In Cell Fracture
I Was Recently Trying Making A 3D Falling Text into The Ground And Breaking Up Into Pieces . But I Had A Problem In Cell Fracturing. When It Is Finished It Was Very Bad.
Before Cell Fracture :

After Cell Fracture:

I Added To My Mesh A Remesh Modifier Because I Think That It Will
Be Better But, Some Changes Only Happened And It Was not Perfect:

Actually This Problem Happens To Me Often In Blender And I Need Help Please. -Thanks-

Thank You All For Helping Me In This But Actually , After A Long Time I Found The Answer :
I Didn't Add Thickness To My Text ,
I Convert It Into A Mesh As soon as I Typed it.

Then I Entered The Editmode And Selected Everything And Extrude Them.

And When I Made The Cell Fracture Without Changing In its Sittings.
And Now :

It Became As You Can See . Not Having Any Problems.
Actually I Don't Know The Reason For This But I Found This Way Which Can Be Useful In This Situation.

- Thank You All For Your Efforts -

Final:

Overview:
As for most of those issues the main problem lays in bad topology.
Example above is made from retopologized Text Object. It's not the best topology you can get but it should show you what you want to achieve finally. Quad based topology.

You can try to use Remesh Modifier. Check:

better Curve/Text to Mesh generation?
Change that convoluted font mesh

But those are examples for Text Object. As for more complicated meshes Remesh Modifier is not working very good.

Take my advice and start making meshes with quad topology in mind. It
  will pay off quickly.

My example was made by deleting inner part of each letter and then filling them with new quads by hand. F2 and LoopTools addons can help you a bit.
I'm not making How to retopologize Text Object answer as this is not a part of this question.

To get rid of the bad default text topology, you could also:
1) Use remove doubles and
2) Use limited dissolve.
This will create n-gons, though, but the final geometry looks much cleaner.
Then you could add optionally a triangulate modifier,
since Boolean operations can handle them a bit better than n-gons in my experience.
And finally you could use cell fracture OR you could use the Fracture Modifier, which gets you better results and is faster, but it is available in a separate build of blender only.
The Fracture Modifier can also operate directly on the text (and does remove doubles and limited dissolve as preprocessing step internally too) , but this might not work every time.
In this case you might convert to mesh, make remove doubles and limited dissolve.
Links to builds are here
https://blenderartists.org/forum/showthread.php?343637-Custom-Build-Blender-Fracture-Modifier
especially check the last thread page for the most recent linux build for example (made by jensverwiebe)
Edit: Result will look like this... with some constraints in Fracture Modifier (FM) and an edgesplit modifier after FM.


text:
How do I make a sunlight in space?
I am Using Blender Cycles, blender version 2.79
My question is very simple, I want a Sun dot light as those images :

I knew a way , But it was very hard and Complicated . So what i want is to achieve the nearest look of the sun only with a simple nodes or with a way that is not hard.

So Is there Any other way  ?

Easiest way is with Glare node in the compositor. What have you tried? What was hard and complicated about it? What renderer are you using? (Blender Internal ot Cycles?)

@cegaton  I am using Blender Cycles, Actually I Used the way in Blender guru Video - Which is very complicated - [How to make earth in cycles][https://www.blenderguru.com/tutorials/earth-cycles] 40:00 time.Sorry , But i don't know the name of the way.What i know that he is using blur effects an  ID masks and others ...


text:
How to fix modeling geometry/topology error after applying all modifiers?
So I have been working on modeling a simple character, and used mirror modifier to mirror my object, but due to some problems happened while modeling, When I applied my modifiers, the part had the problem looks as if my character had a bad stomach surgery

The whole body was very regular and looking very good, but that part looked like really bad thing happend, so my question is how to re-regularize that part again? I don't care that shape of the stomach might differ, I could remodel it or sculpt it, but my goal is to regain those regular squares modeling that part again. I thought of removing all faces that are deformed and form a new big face making loop cuts, but things got very very missy.
Can anyone suggest how to solve such a problem?
I have added my blend file here, in case you would like to inspect the model much more

You should have much less edge loops, did you apply a Subdivision Surface modifier? You should not, use this modifier to smooth your object but don't apply unless you have good reason to (and always keep a non-applied version)

maybe...if you are lucky, there is an xxxxxx_autosave.blend file in your folder with a few minutes before...then just load that and do again the things, you did from then.

Enter edit mode, select the whole mesh, in the menu choose "mesh" -> "symmetrize"
Then select the correct "Direction" in the Redo panel (the pop-up panel with the settings for the tool)
Make sure your objects origin is in the centre of the object as this is where the symmetrize-ing will be based.
Blender docs: symmetrize


text:
How do I make a mirror?
How do I make a mirror in BI or cycles? I have very little experience with materials. I am just wanting to experiment with mirrors in Blender. For example, What I am thinking is to make two opposite walls inside a cube both mirrors. Can blender handle that or even 4 walls as mirrors?

 For Blender Cycles
Go to the materials tab, create a new material, where it says diffuse click and press glossy BSDF. Set the roughness to ~0.

 For Blender Internal
Go to the materials tab, create a new material, tick the mirror box and set reflectivity to 1 or a high number.

This is for the most basic mirror which just reflects. To make a more complicated one, learn a bit more about materials for Blender Internal and for Cycles learn about the types of shaders and the mix node.


text:
Camera Shadow in Cycles live render and final render?
This might be a simple fix, however I have never done close up stills or animations before.
I just started building a logo animation for the company I work for. Barely even getting around to animating anything, I have noticed that a "circular shadow" seems to be following the camera. I have tried turning off the lights, it doesnt modify the shadow in any way.
I've tried researching the issue to no avail. I might be searching in the wrong places, but have not found anything related to it yet.
Below are a couple low quality stills for reference. Has anybody encountered this before? Am I missing something basic?

I am not sure what to make of these images. The camera certainly has no shadow and at least the border you pointed out with the upper arrow in the first image looks like the reflection of a plane used for lighting. Can you upload your file somewhere (i.e. at http://pasteall.org/blend/ ) so we can check your settings? If you are not allowed to upload stuff of your company to official sites, an example file that shows the problem is good, too.

Thank you for your reply @maddin45. I just got back in the office and have uploaded a youtube video demonstrating the issue, and an example blend file. Any help is greatly appreciated. Thank you in advance. Blend file: http://pasteall.org/blend/29479 Youtube: http://youtu.be/4zJn048RQLE

The problem seems to be that the normals of the two faces that connect the horizontal bars of the letter E are pointing into the opposite direction as the rest of the front facing part of the E.

Make sure the normals of your meshes are consistent (meaning that the normals of two neighboring faces are pointing to the same side of the volume, optimally outside).
The normals are used for lighting calculations. Since the direction of the normals is inconsistent over the front of the E, the lighting calculations generate artifacts.
Do you really need these faces? They make the E look like a block. If not you can delete them.
Otherwise you need to flip the normals of the faces or separate the faces from the rest of the mesh. You can flip the normals by selecting the two faces and clicking the Flip Direction button in the toolbar to the right side of the 3D view. If the toolbar is not visible press [T] while your mouse cursor is in the 3D view.

The result should look like this:

To separate the faces instead select them and press [Y].
Both methods ensure the normals of the E are consistent on the front face:

In general you should avoid non-manifold meshes. A mesh is called non-manifold if an edge connects more than two faces. Just imagine your mesh was made out of a rubber sheet. If you can cut out a region around any edge and find a way to press it flat onto the table without faces overlapping, your mesh is manifold and you are ready for production.
If you have a manifold mesh, Blender can even calculate the normals for you: Go into editmode, select the faces whose normals you want to calculate and press [Ctrl+N] to calculate the outwards facing normals or [Ctrl+Shift+N] to calculate the normals facing inside.


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How to fold a plane while keeping length of edges?
Can someone tell me how to fold a plane (e.g. modeling a paper plane)?
Because when I want to fold an edge (the middle line), but have the edges scale... Is there a way to have a pivot edge for the edge to turn around?
I don't need it animated later, I just try to have a folded paper plane with correct texture afterwards.
I know how to get the 3D cursor as pivot point, but I need more of a pivot edge I think?
Also, is there a way to automatically get the folding pivot edges? So you can take a vertex and move it as you would do in real life with a sheet of paper?

Ok, the trick is really pointing with the view through the folding edge path...
The first fold worked - but the second one is a new problem:
The selected vertice has to go to the crossing of the circle and middle line - with rotation of course because of the UV...
So how can the folding edge be created/found? Is there a way to lock the edges from the selected vertice in terms of length?

Today I tried some geometry to accomplish the problem: generate the folding edge... but I don't know how to get a vertex in the crossing point of the 2 lines here (2 orange selected edges crossing - i need a new folding edge from top tip to this new point to fold the side) - Any suggestions?:

Welcome to Blender SE cheese!
While rotating the vertices around the fold, you must align your view so that the fold points directly away from the view. All vertices along the edge occupy the same point on the screen.
Now, you can set cursor to folding line, set pivot point to cursor and rotate.
Unfortunately, it is not easy to exactly align your view. If you need full precision you can create extra geometry and then align your view to it. Then remove the extra geometry.
Start like this:

Extrude a corner vertex at the end of the folding line. Right click directly to extrude it on top of the original.
Using the opposing vertex as cursor, scale the extruded vertex up some.

Now extrude that edge to create a face. Extrude the face to create a cube.

Select the face point away from the fold and hit Shift + Numpad 7. Now, your view is exactly aligned to the edge. Rotate the outer vertex.

NB! Extruding the edge the right way may be hard sometimes. You can experiment some and see. I'm not sure.
If you don't need exact precision. Align you view the normal way and rotate away.
Good luck!


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Vertex normals incorrect, but face normals look correct?
I recently imported an FBX from a Max export and about 90% of the model looks fine but for some parts, the vertex normals are 'twisted' even though the face normals look correct. As far as I can tell the parts are all manifold and the bad mesh in the image below is just a simple cylinder so I don't think its possible for that to be non-manifold, right? Also when I tried to select non-manifold, nothing selected.
I added a new cylinder for reference and those verts look fine. How can i 'reset' the weird verts without remodelling these parts?

Have you tried the Clear Custom Split Normals Data button in the Properties Window > Object Data Tab > Geometry Data Panel? (It is only visible if there is any custom normal data stored)

@DuarteFarrajotaRamos - AHA! Yep that was totally it! I have never needed to use that button before so i had no clue it was there. If you want to add this as an answer i'll accept it. Thanks!

Will do, posted as answer

You should post that information as an additional answer bellow instead, it's more coherent and could be helpful to someone else searching for answers.

Those are probably custom normal data imported from 3Ds MAX
Try the Clear Custom Split Normals Data button in the Properties Window > Object Data Tab > Geometry Data Panel (It will only be visible if there is any actual custom normal data stored)

That was it. Thanks a lot! I have had this issue before and always just remodeled those parts. You have saved me a ton of time =-D

So your answer did put me on the right path, but I had to do one more step. After clearing those split normals, Some were still split but not nearly as bad so I added new custom split normals and it seemed to fix the issue. Does that sound right to you?  I updated my post to include the images but figured I'd add a comment to this for clarity.

I'm really not very familiar with the custom normals workflow, I don't personally use it very often so not sure it is actually right or not. Anyway you should consider posting it as another answer bellow for the sake consistency and clarity instead, as it might also be helpful information for other users with similar problems

Thats fine, now that i know what to look for I can do some more digging. And I followed your advice and posted another answer. Still keeping yours as chosen answer because it led me in the right direction

Don't worry about it, if you feel my answer is incomplete you can mark yours as correct instead, no hard feelings

So I am still sticking with the answer chosen, but I had to do one more step to completely fix the issue (I think). When I cleared custom split normals data, most normals were fixed but some were still split (not as bad though):

So I decided to try adding custom split normals data and when I did, it cleared up those other split normals.


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Active Camera do not update 3D view camera view
Having a very weird issue with Blender 4.0 and no matter what I Bing or Google, I do not see a solution posted anywhere about it. And have browse all over this site and cannot find a solution to my issue. With that said, here it is the issue.
Here is a copy of blend file with only a cube of course.
Normal Camera Behaviour: On Blender 3D view, when you press Numpad 0 toggles the camera view, then if you navigate into Properties > Scene > Camera and select a camera, the camera view changes to that selected camera. Correct?
The Issue: Not now. The issue I'm having, and I cannot say how to replicate it because I do not have a clue how it happened, what combination of keys I might have clicked or what else done caused it. So now, when I change camera on the Scene Tab, the camera view in the 3D view do not change to the selected camera. Stays with the camera that was active initially when Numpad 0 was pressed.

Of course, when something like this happens, the first thing I do is to check if Local Camera property has been activated and have an object or a camera selected hitting Ctrl+0 by accident, but it is not the case.

I also tried to select the camera by making it active in the Collection Tree Properties with the same luck. This would be same action as selecting an object/camera and set it as an Active Camera View. But it does not change the 3D view camera.

Granted, when I do the changes, the camera selected is the camera used for rendering. That's not the issue here. The issue is in the 3D view, when I switch cameras, I want the camera activated with Numpad 0 to change to the camera selected on the Scene > Camera tab, which I use often to make sure changes that I made to the objects do not conflict with camera position and angle. With this issue, every time I change a camera in the properties, to see it active in the 3D View viewport, I need to toggle Numpad 0 each time.

This consumes a lot of time, especially when I have to work with 250 scenes in a very limited time.
I am pretty certain that a combination of keys I pressed might have caused the issue, but I can't find anywhere, not even in the Blender manual online, of a process that I can use to reset this to its default behavior.
Any help will be greatly appreciated, thanks for taking the time to do so.

Hm, that's strange. I would have suspected the Local Camera is enabled since some users do not know about this feature. Could you upload your file to https://blend-exchange.com and edit it into your question? I guess the model is not the necessary (because I do not think it causes this), just the scene with its settings, the cameras and probably a default cube to look at should do...

It is very likely because you are in the isolation mode (/ on numpad).
This happened to me, and the 3D Viewport update camera view between cameras in one click again after i quit isolation mode. This happens in 4.2 and I don't know if other versions suffer from this issue.

That was it, just that simple. The slash on the numpad was the trick.


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Blender in ElementaryOS installed from most recent 2.79 build
I installed most recent blender from ppa:thomas-schiex/blender to get the most recent blender version. Starting blender now results in crash. Running blender inside terminal from directory /usr/lib/blender leaves me with
Fatal Python error: Py_Initialize: Unable to get the locale encoding
ModuleNotFoundError: No module named 'encodings'

So far I found out that I need to install python sources. To find them I installed Synaptic Package manager and searched for them and couldnt find them. Therefor I also ran
apt-get source python

I still get that error when I start blender from Terminal.
Perhaps anyone knows how to resolve that?

Others seemed to have a similar issue as well but couldnt resolve it: Blender with system python failing
Here is my solution also posted over there:
All right... I had the same error appearing today and I have been able to solve it. It's been pretty easy. After removing blender and installing blender from ppa:thomas-schiex/blender There were some files still around.
To make sure everything works try:
sudo apt-get purge blender
cd /usr/lib
sudo rm -r blender
sudo add-apt-repository ppa:thomas-schiex/blender
sudo apt-get update
sudo apt-get install blender

Since everything is purged AND manually removed from versions installed manually it should be fine now. Have fun  :)


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Material Baking results in some black faces
I need to bake something for a unity project. Unfortunately I had an issue I ran into. I could solve it in unity but since this seems to be very odd I want to understand why this happens.
Here is a picture of the unbaked material:

Here it is after baking with an image node connected to an emission node:

Here are my bake settings:

I also tried it with only Diffuse / Color. The result is a mostly black image. Some faces are greyish:

All the other stuff I baked so far - I had no problem with them.
What I tried so far:
- I unwrapped it again
- created a new image to bake it to
- recalculated normals
Thank you for every info you can give me on that.


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Loop Tools Addon
Cant find a loop tools addon. On the offical page only link on empty directory. Im searching everywhere. Can anyone give me link?

Afaik, LoopTools are built-in now. In 2.76b they are at least. No need to downoad them. Try searching LoopTools in Add-ons tab in User Preferences.

Looptool is actually bundled with Blender now (it has been for a while, but I'm not sure quite how long).
To enable it, go into the users preferences and then addons. From there, use the search box to search "loop" and then enable the addon.

To use it, in edit mode, press W and then go to the looptools drop down.

if you have latest builds of Blender, loop tools is included:
on edit mode, press W, loop tools
https://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Modeling/LoopTools

Thaks bro's. Im so stupid that can't think this so easy)

authors: Сергей Лебедев


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Need help trying to project shape onto cylinder...
I'm trying to take this cylinder and circle combined shape and remove it from the pyramid so the pyramid has a hollowed out shape. Tried to do it with boolean difference, which didn't work and now I've tried knife project. Which also doesn't work. For some reason the cylinder shape doesnt seem to be registering as a usable object?

Not sure how to do this, but Knife Project didn't work because the object acting as the knife must have no faces, for an example, create a plane, select the plane in edit mode then press X and then remove only faces. That should allow the knife project to work.

Welcome to Blender.SE! I'm not sure to get exactly what you would like to do: project a shape or booleand difference between two solids?Are both object watertight meshes? Maybe you can upload your blendfile to http://blend-exchange.giantcowfilms.com/ so it can be inspected.

Possible duplicate of Why doesn't the boolean modifier work for me?

Hi guys - Thanks so much for your help. I'm obviously a complete noob here. What I'm trying to do is to remove the cone/sphere object (which is two objects joined together) from the pyramid. (So there will be a hole shaped like the joined object in the pyramid). I tried removing the faces, and the knife projection worked however what resulted was just a glitchy mess, with no actual indent in the pyramid.

I somewhat remade your scene, and was successful so I will contribute what I did. I think what may be causing you the biggest problem is the lack of geometry in your pyramid object. Try adding several loop cuts to support the boolean operation.
Here is what I did:

Default cube, enter edit mode select top face and scale to 0 and scale as needed to create the pyramid object. (I also scaled the bottom face slightly).

Add several loop cuts in each direction with
Ctrl+R

In object mode, add a uv sphere, then go back into edit mode and
enable proportional editing by pressing O and select only
the top vertex.
Move the vertex on the z axis until you have the desired shape, and then scale to size.

Go into object mode and align the sphere object with the pryamid
object, and add a Boolean> Difference to the pryamid object, setting it's target to the sphere and delete the sphere from the scene or move to another layer.

After following these steps, also an edge split and subsurf modifier added- this is the result:


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How to remove a hole from a solid plane?
I have an object with a solid plane and multiple holes in the plane:
Now I want to remove only a single one of these holes. How to do that?
Thank you very much!

Select the faces around the holes that you dont want press x and then select the edge loop and press f for fill the place again.

An example including keys to press would be useful

Using Circle Select, select all vertices of one side of hole (drag circle around hole).
Right click and merge vertices at center.
Repeat previous steps until only one vertex remains.
Right click and dissolve vertex.
Repeat process for other side of hole.
Results in clean planes.


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Orange squares appearing on render?
I'm trying to render a scene in Blender, and as of yesterday (it was not doing this when I was working on it 2-3 days ago), I am seeing orange squares dancing around the rendered image. Google tells me that these are render tiles (I think), but what are they, why are they there, and how do I get rid of them?

You mean while you are rendering? Those just show what tile is currently being rendered.

If you are trying to render an animation, you need to specify that. You can view your animation by slicking 'view animation', or you can create an AVI.;http://blender.stackexchange.com/questions/15142/how-to-render-an-animation-in-blender

I'm not actually trying to render an animation, just a still image. That's another issue I'm having, blender seems to be rendering frames of an animation when I don't intend to create an animation. It goes on and on with rendering and re-rendering. Is there a way to stop it from rendering so many times? I don't think I keyed animations at any point.

@user2828965 What render engine are you using? If you are using BI, do you have motion blur or FSAA enabled? Or multiple render layers?

Figured out what was going on with the rendering of an animation. I was actually hitting ctrl-F12 (render animation) as opposed to just F12 (render image), hence the confusion.

They are just indicating the currently rendering tiles:

AFAIK there is no way to turn them off, other than disabling tiled rendering (anyway, IMO they are quite useful).
To disable tiled rendering in cycles, enable progressive refine in Render settings > performance:

To disable tiled rendering in BI, make the tile size at least as large as your render:

Note that disabling tiled rendering will increase render times, as in most cases rendering many small images is faster than rendering one large image. See Are there any advantages of bigger/smaller tiles.

Thanks for the explanation. What's weird is that I never noticed them when I first started working on my model. Do the orange tiles become more often visible when you have a more complex model?

@user2828965 No, they are always there.. The only time I can think of when they weren't there in older versions of blender (I think they were added somewhere around ~2.64? I'd need to look that up though).


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Is my fire animation rendering right?
I'm trying to make an animation of fire, but while it's rendering it just looks like a big gray box where the fire is supposed to be. Is this normal?

I feel stupid now.

Wait. That wasn't the problem still looks like that, please help.

will you add a screen shoot of the material nodes for the material on the smoke domain.

It looks like the domain object has a diffuse shader applied to the surface.  Smoke domains should only have a volume shader (using a density attribute node).

@someonewithpc That will hide the smoke too.


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Compositing versus video sequence editor for combining video file with own animation
I need to make a video where I take a movie file and add some of my own blender animation to it. Last time I did this I did the whole thing as a standard blender animation, with a "screen" object in my scene which had a video texture. I realise this is not optimal and that there are at least two better ways to do this: compositing or using the video sequence editor. I have not used either. My question is, what are the pluses and minuses of each of these ways? Can one say that either is easier than the other for a novice to pick up?

I also would use the compositor for it, but it is more easy in video sequence editor. But like Mike Pan wrote you have more possibilities in compositor. For a high quality-merge you will need the compositor for a simple overlay the sequnce editor is ok. hope it helps... ;)

The sequence editor is designed for non-linear editing. While it has some basic comp features to layer images on top of each other, you do not have the level of control that you get with the compositor. For anything but a trivial overlay, I highly suggest using the compositor for the task.

Thanks a lot for a useful answer! Not enough rep to upvote!

Actually you can use both. The output of the compositor is available as the "Scene Strip" of the video sequence editor, provided they are both enabled in the render tab (which they are by default).


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Render times for standard non-3d video?
There is a lot of info on how to speed up 3d rendering, but not for standard video as I'm starting to use it.
I'm doing just a few crossfades, mastered audio done in another program, with 1920x1080 resolution of about 1 hour of video at 60fps.
This is pretty high quality video, so I understand it would take a bit to render.
However, to render to H.264, it took 6 hours.
Is there anyway to reduce this? I would do lossless, but that takes nearly a terabyte of space.
Note, my encode settings are a bit rate of 8000, 60fps, 30 GOP, and 384 audio AAC.

Rendering from the cli using the background option can free up some ram and skip un-needed gui updates. In preferences->system there is a memory cache limit for the sequencer that might help.

Also, if you have multi-processor system I found that Blender does not utilize that very well. What I found to help was to open i.e. 4 instances of Blender (I have 8 logical cores) and render in parallel different parts of movie. Then you can stitch them with something like avidemux.

You're probably also limited by your HDD and RAM speed.

Lots of speculation, so I decided to do some some tests on the sequencer performance:

Performance Options
Global Prefetch set to 30frames, 4096MB of cache, AVI JPEG 50% quality: 2m28s
+ UI Locked and no image Display: 2m28s
+ Sound track caching, MPEG seek per-track set to 60 rather than 25: 2m28s
+ Immediate re-render, to test for effect of disk caching: 2m28s
Conclusion 1: Surprisingly, none of the performance-enhancing options seems to do anything.

Encoding Options
Same setting as above, AVI JPEG: 2m28s
+ Encoding set to Quicktime H264 @ 50% quality: 4m08s
+ Quicktime H264 @ 75% quality: 4m02s
+ Quicktime H264 @ 95% quality: 4m11s
+ Encoding set to FFMPEG H264, H264 Preset @ 600kbit: 8m18s
+ Encoding set to AVI RAW: 1m58s
Conclusion 2: The encoding engine makes a huge difference in speed. AVI RAW is the fastest if you have the disk speed to back it up. FFMPEG H264 is the slowest.

Quality Options
+ With antialiasing, AVI RAW: 1m58s
+ without antialiasing, AVI RAW: 1m18s
Conclusion 3: Antialiasing makes a difference, but the quality loss is huge, especially when all the input clips have different resolution.

Test Details:
Scene used: 2000 frame long sequencer with 6 different 720p MPEG4 video input, 3 1080p PNG sequence inputs, dozens of images, dozens of transitions, 1 audio track. Output is 720p with Antialiasing.
Test Methodology: System is restarted after each test, so the effect of disk cache is minimal.
Test system: 2.2Ghz i7 Macbook Pro, 8GB RAM, Radeon HD6750, 500GB SSD

Unfortunately, there's not much you can do. Tweaking the settings to reduce quality might help some, but not much. You can reduce the number of frames you render by changing the frame rate that you're rendering to (30fps is more work than 24fps), but that may not be an option if it doesn't give you the result you want.
The problem is that this kind of rendering is a really simple, relatively brute-force process, so there aren't many opportunities to optimize on the user's end.
The main things you can do to speed thing up are hardware related. Defrag your hard drive so access times have the opportunity to be shorter (only applies if the files you're accessing are fragmented). More RAM will make it easier to fit all the relevant files in RAM instead of virtual memory. A faster hard drive will make virtual memory faster and will make loading files faster. A faster processor will make the calculation of cross-fades and other effects faster (as well as all other operations).
Beyond that, it'd be interesting to do some benchmarks to see if there's any difference between the same quality settings for various codecs. I can imagine that some codecs require more processing than others, but I have no way to make any guesses about which are faster.
Incidentally, I recently did a job making a 4-min animation and it took about 30 minutes to render all the raw frames into a single video (with a whole bunch of cross-fades and whatnot). So it doesn't seem like your times are unusual or unexpected.


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when i try to uv unwrap my mesh , blender hangs and become unresponsive, why?
I am new to blender, when i try to uv unwrap my mesh, blender hangs and become unresponsive. the mesh has nearly 35000 faces. it is a subdivided sphere which i used for sculpting.
when i uv unwrap a simple cube , it works fine. is there a workaround for this, or a better alternative way to apply texture?

Which option are you using to unwrap your mesh?

i used both the normal unwrap and sphere unwrap

i have also increased the TdrDelay of the graphics card to 10, but it still becomes very slow. is this problem only limited to me? can you do uv unwrapping for large models in blender?

While blender is processing the interface will freeze up. Try giving it a few minutes. Or subdivide after unwrapping.

That may be dependent on your computer configuration or blender version.

yes, as gandalf3 said, i first unwrapped the sphere and then subdivided it, and it didn't hang this time, but became a bit slow.

Potential Solution: Smart UV Project

Although I've never tested this method on a UV Unwrap task that has crashed Blender, I've found that using the 'Smart UV Project' option is much faster using the normal 'Unwrap' function.
I found this when unwrapping the mesh of an ANT Landscape body, where it would take several unresponsive seconds before Blender processed the unwrap using the regular unwrap function.
However, when I unwrapped again using the 'Smart UV Project' option (with the default parameters), it was almost almost instantaneous.
I know this is a pretty old post but I'll leave this here just in case anyone finds it and gets help from this answer. (Hope I haven't broken any community forums by 're-opening' an 'archived' thread.)

To whom it may concern:
I had this problem, and my error was that my .obj file contained duplicated vertices. Unwrapping wouldn't finish in an hour even. But then I found that I needed to go into edit mode, select all, and right click -> merge vertices -> by distance (default settings worked fine). After this preprocessing (which also reduced the file size - I won't complain about that) the unwrapping finished in a matter of minutes. Additionally, in my case, "Smart UV Project"  (with an island margin of 0.001 just to be safe) turned out to give much better (more compartmentalized) results, and after merging vertices, this operation didn't take more than a couple of seconds.
Just to be clear - even the smart uv projection didn't terminate until I tried merging vertices. Merging the vertices is key.


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Capture and restoring the state of an area and the mode
Looking for a Python solution - Would love to make some basic macros using the Blender addon "Pie Menu Editor".
Premise: How to store the current areas and mode state of Blender so it can be returned back to that stored state if changed.
example:
State 1: 3D view in edit mode Captured state.
State 2: User switched 3D view to Shader Editor.
State 1: User calls back the original state.
Thank you.

Do you simply want a change of the layout, or do you also want to revert any changes made?

An example of this would be:
Dragging the timeline indicator in edit mode. On mouse down, you need the mode to switch to object mode. Then on mouse release, you need to return back to edit mode.
The same would go with using the arrow keys for the timeline cursor/ indicator.

Current mode.
Perform a task.
Switch Mode.
Finish the task.
Switch back to the original state.


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Splitting geometry of two models which are merged together
I have a obj file which contains a basic model with two various versions of it you can see here:
.
This model contains a grey/teal/blue model (Darkwitch) with their textures and a purple/orange one (Kuralak). Unfortunately both versions have different geometry like the horns and shoulder which only belong to the Darkwitch. Looking through the texture files you can see that there are several materials for this model:

Even though I know that it really depends on the model/file itself I would like to know how I can have a look at the different geometries trying to separate them? Or is it somehow possible to make all other textures transparent so only the Kuralak model becomes visible?

When you have one mesh object and you want parts of it to be hidden in object mode depending on some chosen options you can use a mask modifier.
To make use of the mask modifier you first setup some vertex groups, you may be able to do this by selecting based on the material applied, otherwise you need to select different vertices and add them to a group.
Once you have the vertex groups setup you can add a mask modifier for each group, then you can easily turn on/off the different parts.

The mask modifier shows only vertices in the selected group, clicking the arrows next to the vertex group name inverts this so it hides the chosen vertices.

Apparently there were no vertex groups at all so I might have to create one based on the materials applied. Do you have more information on how to do so?

That's good for a new question - create a vertex group and assign the selected vertices to the group.


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Blender 2.8 Focus view on selection
When i press . view goes to center (no matter which object i selected) and not to selected face/object. Is it bug or what?

I investigated more and found out that problem is with my .blend file. When i create new everything work fine. But this file on different machines behave the same

Appending collection from broken file to new did the trick. Everything works fine now


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Light trough the object on render
I have lamp model and point light inside of it. You can see lights on preview, but i can't see the lights on render. How to make them glow correctly?

There are numerous possibilities as to what causes this. I tried to list them in order of likelihood

your material for the lamp's glass material does not look transparent (you can set it to translucent, but be ready for some serious noise)
your lamp is too weak for cycles
your lamp's cycles visibility options don't make it show up where it's supposed to illuminate.

There's more, but please make sure the ones above don't apply and if not send another screenshot with the lamp selected, meaning showing its settings as well as its place in the outliner.

I do not have your blend file so i can not tell you exactly what can be the reason but still
I think you have not added correct Material for lamp glass
you should add translucency in it so that light can be visible out of the lamp with glow.
and also try reducing the size of point light


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Control the rotation of an environment map
I use the following node setup for world settings:

Notice the keyframe on the z-axis in the mapping node. At the end of the animation, the environment map will be rotated by a full 360 degrees.
The rotation defaults to a bezier curve, which I don't want - I want to switch it to a linear rotation, to be able to create a continuous loop. However, this animation never shows up in the graph editor.
(I understand that the graph editor shows only curves on the selected objects, but how do you 'select' the environment map? You can't even click the 'world' entry in the outliner.)
Is there any other way to control the animations behaviour?
I am using Blender v2.75.

Select the mapping node in the compositor, then go to your animation scene, to your graph editor and you can change it to linear.


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can we render only audio in blender?
I want to cut a portion of audio file and render in mp3 or aac, but in render tab i can not find any settings for this. i also went through this thread:
http://blenderartists.org/forum/showthread.php?247012-Render-Audio-Only-in-Blender
But i can not see any button called "mixdown" in the scene tab. I am using version 2.74. so is it possible to render only audio?

Yes! You have to go to the render panel, then under the render panel and click on the audio icon (next to render and animation).

Then you can choose different audio outputs and settings (on the left at the bottom of the screen under the tab mixdown).

And then you push the button mixdown (at the top right).

In Blender version 2.81 you have Menu -> Render -> Render Audio.

The question was about 2.7x

@Lukasz-40sth I don't think there's anything wrong with adding the 2.8 answer as well.

@Ray Mairlot: The answer should give 2.7x solution first with optional 2.8. Like: it is/isn't possible and in 2.8...

@Lukasz-40sth The other answer gives the 2.79 version.


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Modal operator mouse over event
I'm working on an addon that generates buildings based upon a base mesh.
Presently, I'm hoping to add a feature that allows the user to very quickly create the base mesh using a modal operator, whereby they would be able to extrude the base mesh in fixed increments by clicking and dragging the faces they want to extrude.
I want the operator to check if the mouse cursor is over a face on the base object, and set that face as the active selection. Anyone done something like this before? Any help you could offer would be greatly appreciated!
(Note: If there's a more efficient means to the same end, I'm very open to suggestions!)

@NoviceInDisguise, not quite, but that's pretty cool! I could think of quite a few applications for a tool like that. The tool I'm working on will be primarily for the purpose of creating individual buildings. It was something I needed to do to help speed along the development of a game project, but I decided to keep going to make a fully-featured addon! In the end, the user will be able to generate custom textured buildings with baked AO and textures ready for export in to a game engine!


text:
How do I make an object in my scene into an object I can instance using python?
I'm in the process of writing an addon that generates buildings based on a group of assets such as bits of wall and roofing.
My current plan is to somehow dynamically save custom assets, including UV coordinate, textures, etc. to an object that I can create using python. (Much in the same way objects are typically created in python, only they would be defined by an object in the scene, rather than pre-defined by another piece of code)
For instance, when I want to create a Monkey with python, (and who wouldn't?) I can just call bpy.ops.mesh.primitive_monkey_add() and viola, I have a monkey. Is there a way to take my active object and dynamically create a function that is able to recreate it?
Feel free to ask further questions on my dilemma, as I feel I may not be explaining it very well!
Thanks!

You could select you own object and create a Group

Select your object(s)
Ctrl-G to create a group
After that you can create instances of this group by calling:
bpy.ops.object.group_instance_add(group='GroupName', view_align=False, location=(0,0,0))


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How difficult would it be to implement on-the-same-track transition?
I'm talking about the VSE. Right now you have to waste 3 (3!) tracks in order to make a transition between two clips; the first two of the tracks you use for video strips and the third one is for a transition strip itself.
As far as I know, there is no addon that let you make transitions on the same track. If there is any, please let me know. I don't know is that even doable with python or you should code it in core components and compile afterwards.

If you are transitioning from one clip to another, you only need one track. Position the tracks in the order you want. Select the first clip, then shift select the second (both tracks selected). Now add a cross effect. Right click on the end of the first clip or the beginning of the second clip. Now hit "G" and move the selection to the desired length for the transition.

I guess they changed it. Thanks. Could you please tell in what version they made it possible? 'Cause in new version it does work, but in older versions you had to add a strip and place it above two other strips and all the hassle.

It has been this way for many versions. I never knew it to be a problem, but I didn't start seriously using the VSE until the last year. I have ditched several video editors because Blender does it quite well.


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Cycles. Masking objects with shaders (no compositor)
Starting off I want to clear it out that it may be a duplicate question, but in fact it is not.
1. Here's my previous question Cycles. Masking shader. How to make objects disappear in plain sight.
2. Here's the one using the compositor Mask out certain objects?
3. This one uses Blender Render Mask single object
Problem description:
I need to be able to mask out (make it completely transparent) certain objects in a 3d scene. An object placed inside another object's volume (masking objects are closed mesh, water tight, manifolds) should be transparent. If only a potion of an object is inside the mask (masking object) then only that portion is transparent (invisible on the render).
The main use of this is for motion graphic designs.
Demonstrations of what is needed: (imitated with booleans)
The masking object has only one shader - transparent.

Solutions that don't fit and why:

The question at the first link[1] was by me, and the answer
was to use Transparent Depth as a factor.  The problem with
that solution is that it doesn't care whether an object is inside
something or not, it just renders transparent everything that comes
after the transparent surface (the surface of the masking object)
 As you can see,
from one side it's fine but when rotate the view so that all our
objects are behind the masking one, everything that has that shader
setup is transparent.
The answer that is given at the second link[2] uses render layers and as a consequence requires compositing. When you work in 3d and have a production scene with many objects that grow out control, that approach is simply not suitable.
At the third link [3] the solution is provided only for the Blender Render and also uses fixed coordinates for a "faked plane" which is done in nodes, not taking into account any real geometry at all.

My thoughts and commentary:
The masking object has only one shader - transparent.
Maybe there is a way to input the geometry of other meshes through pynodes and somehow use it as a factor in mixing emission and transparency.

Why are boolean operations not working for you for that purpose?

@Bruno 3 things:

not all objects can be used with the boolean modifier
when you have a production scene with lost of objects it's really difficult to keep track of all the objects, masks and modifiers
sometimes there is a need to use not a "shadeless" material and booleans tend to create bad normals from time to time which can halt the whole project

right about boolean. Regarding Transparent depth, have your tried playing around using 1 < depth < 2 instead of just 1 < depth? Shouldn't it make objects reappear if light rays go through multiple transparent layers?

@Bruno i think lemon's answer provided just the approach that you're taking about, if i understood you correctly

Using Cycles, you can achieve this by combining transparent depth of the light path node and backfacing of the geometry node.
We want to be transparent what has a depth modulo 2 equal to 1, as we want to be visible what is behind the transparent object (all are considered manifold).
But back faces have an additional transparency depth because they can be behind its own transparent front face.
So we add the two (backface + transparency depth) and set transparent what is modulo 2 = 1.
Here is an example:

Note that in the provided blend file, if the two transparent cubes overlap (intersect), the blue one will reappear. But the two transparent cubes together are no more manifold when overlapping.

do you think there's a way to make the masks interact in a manner of a logical OR gate (inclusive OR)? so just overlapping wouldn't cause the masked mesh to reappear.

You mean when the two transparent cubes are intersecting? I don't think it is possible as the shader does not know (and can't know) about the geometry that is masking it.


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Create sharp crease in smooth Mesh
While modeling an Audi R8 I have the following problem. The thing I want to create is seen in this image:

I want to create a sharp crease (outlined in red) which starts around the first exhaust and then goes to the second.
Is there an efficient way to do this (I also use the Subdivision Surface Modifier for this model).

I think this is more a duplicate of this question

@gandalf3 I knew the thing with changing the Mean Crease but I thought there would be another way. But now I tried it with a Loop Cut and it looks pretty good.

In order to specify what the subsurf modifier should smooth and how much, you can use the Mean crease setting. This will allow you to (basically) tell the subsurf that it can subdivide an edge, but leave it sharp (instead of smoothing it). There are other techniques for getting sharp edges in an organic model workflow, most of which are discussed here.

It discusses using more edge loops very close together, which is effective, but very inefficient.
It discusses using weighted creases (which is what I recommended above)
And it discusses the edge-split modifier

...all of which are effective tools for making sharp edges. Each has its benefits and draw-backs.