text:
Display array value as emission material using python console or script
Let's say  have an array of CSV-style RG values, something like this:
[0.1,0.5,
0.2,0.7,
0.4,0.8
0.8,0.5]

Here, the odd elements are always red, and the even ones are green.
Is there a way to display the values sequentially, where every frame would use both the red and green values in an emission shader? Thanks in advance.

Do you mean you want the red and green values combined into a single color used in one shader, or that you want separate red and green emission shaders.  The first could be done with a python script that advances the current frame, sets the R and G of a combineRGB node and keyframes the result.

@MartyFouts Yes, i want to combine the values into a single color. How would the python script for this look?

answer tested and added

One Way to Do It
This is a question where a judicious mix of Python and preparation go along way.
You could write python to create an object, add an emission shader to it, and give the shader a combineRGB node and there are question here that will show you how to do that.
But instead, let's manually add this material to the active object, making it the active material:

Now we can use your array to add keyframes periodically setting the red and green values from the array:
import bpy

# https://blender.stackexchange.com/questions/252346/display-array-value-as-emission-material-using-python-console-or-script
# An array of R and G values for the emission shader.
rg = [
    0.1,0.5,
    0.2,0.7,
    0.4,0.8,
    0.8,0.5,
]

frame_insert = 1 # Start adding frames here
frame_delta = 12 # every Nth frame

# Assume the active object's active material already has an emission shader
# that has a Combine RGB node, so get these things.
object = bpy.context.active_object
material = object.active_material
nodes = material.node_tree.nodes
node = nodes["Combine RGB"]

# Walk through the array, adding keyframes
for index in range(0, len(rg), 2):
    node.inputs[0].default_value = rg[index]
    node.inputs[0].keyframe_insert('default_value', frame = frame_insert)
    # Delete the below line if you want interpolation
    node.inputs[0].keyframe_insert('default_value', frame = frame_insert + frame_delta - 1)
    node.inputs[1].default_value = rg[index+1]
    node.inputs[1].keyframe_insert('default_value', frame = frame_insert)
    # Delete the below line if you want interpolation
    node.inputs[1].keyframe_insert('default_value', frame = frame_insert + frame_delta - 1)
    frame_insert += frame_delta

How it Works
frame_insert is initially set to the first frame where you want a keyframe for the pair of values.
frame_delta is set to the spacing of lighting changes.  You can set this to one and get a really annoying flicker, but if you do see the bit about why two keyframes are added for each change.
Next, we rely on wanting to do this with the active object's active material, so there are four lines of code that find the object, the material, and the CombineRGB node.  If you want to create these things, this is where you would do it.
The loop assumes the array in the format from your question.  You'll need to change the loop parameters and indexing if you want to use a different format.
The key feature is that the Red input of the Combine RGB node can be set by setting the node's inputs[0].default_value, and likewise the Green input is on inputs[1].  So we set the value and add the keyframe, using keyframe_insert.
The reason to advance to just before the next place we want to add a keyframe, is to keep the intensity constant over the whole interval.  There are other ways to do this, but this is the simplest in this context.  If you want to let Blender's animation interpolation vary the value, delete the two keyframe_insert calls that use frame_insert + frame_delta -1.  Definitely delete them if you want set frame_delta to 1.


text:
Needing to separate two meshes while keeping some parts stuck together
I'm following tutorial of making a car. If you scroll up to 38:30 you can see he separate the two meshes, and a bit later want us to connect some parts of the mesh together while keeping them two different meshes. I tried using the move, fill and merge tools, but they don't seem to give the same results. It would be easier to work if the two meshes are one object, but I will need them to be separate for later steps.
Blender file
In short, how can I make it look like this
When it's like this

I don't know what he does in the video but you can't connect meshes that are in separate objects if this is your question

Should I edit it as one object and do some workaround in the future steps where I need them to be separate?

it looks like he wants to use a modifier on the separate object, that's probably why he separates this part, when he will have finished he will probably join the parts again

I will try to do it without separating the object. Thank you for helping

source: Stack Exchange

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

sort: votes


text:
Weird white and black boxes in model
So I was following a tutorial for beginners and I reached a point where I was using texture paint. After I finished I noticed a weird white and black boxes. I looked it up, but couldn't find a answer.

Welcome to the Blender Stack Exchange.  When you have a problem like this, it can be helpful to post your blend file on the internet and then link to it so that people trying to help you can do so as quickly as possible. When following a tutorial I'd usually suggest linking to it, as that might provide helpful information to the responders, but in this case we're probably all aware of what tutorial you're talking about.

It's because your Image Texture you are using to color the donut has some diferent color in the corners so that part where you see the grid type patern is where the corners meet.
To fix this:

You sould can paint all the corners with the same color

An image of a donut I made to recreate the problem:

Oh I didn't think of it this way. Thank you!

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


text:
How to view keyframes of objects that have visibility turned off?
I am making a gun that shoots lasers so I am keyframing the visibility to turn on and off. The problem is when the object is disabled in the viewport, I can no longer see the keyframes in the timeline. This makes it especially hard to adjust things since I cant see when the bullets turn on and off exactly.
I could just keyframe the rendered view but that makes it even more trickier because bullets could be showing in the viewport but not in the render. Having a bunch of bullets lying around the scene also makes it difficult to know what exactly is going on or if the gun is even firing. Having a point light attached to the laser that must also have its light enabled/disabled complicates things even more.

If you are using the Graph Editor, you can disable Show Only Selected and enable Show Hidden, this way you can see the keyframes of hidden objects. The same applies in the Dope Sheet Editor.

That sort of works. But it reveals all keyframes in the scene which populate the viewers making it very difficult to work with when you have a complex scene.

@Mike Sure, otherwise you would need another toggle setting for each object, visible in graph editor or invisible in graph editor (which you actually have). If you have too many objects and are not willing to do that manually on all of them, I'd go with Chris' method. As he said, if you have just one material for the laser there's only one thing to manipulate.

Why don't you just animate the materials alpha? and instead of changing from 0 -> 1 (which you can do at last step) you animate from .3 to  .7. So you still "see" everything in the viewport and you can still differentiate between "on" and "off" and you can still work with keyframes. If you are satisfied with the result you just change the alpha value from 0 -> 1. And since the "laser" materials are "normally" just 1 or a few you don't have to change a lot.

For some reason alpha values aren't working for me. when I set alpha to 0 on a material it renders the laser as solid black

you have to set blend mode in material Settings to Alpha blend or hashed


text:
Rotation and scale Changes appear to not save with Linked object
I have a set of objects that I am importing into a main scene via linked connection. For some reason the changes I make to the rotation and sometimes the scale of these objects are not being saved. Particularly the root parent.
I have reloaded the objects back into the main scene many times after rechecking everything. I make sure to apply the rotations and scale throughout the hierarchy. For instance I am trying to align the object to the X axis.
In the object file the orientation is correct

In the main scene file the orientation is off

Hello, the arrow in the middle of the link icon besides the objects and collections names in the outliner means they are library overrides. Try right clicking in the outliner > Id Data > Delete Library Override or just in the transform channels > Remove overrides

It seems to have fixed itself after I restarted the computer.


text:
Wall takes up lighting only in specific camera angles
In my blender file I have a problem with the the way the wall catches the shadow/light. In previous renders this worked completely fine
previous render,
but when I switched to blender 3.0 the lighting seemed to change.
Here a short video on how the light changes with the angle of view.
showcase of changing shadow
Here is the material shader node setup, the render passes and the seetings for the main lightsource.
Thank you very much, I appreciate any kind of help!

Hello and welcome. Please use the built in tools
to add images to your question. Use an image editor, or online
optimizer, if you must resize an image. You
can help those who would answer your question if all the information
is displayed as part of the question and not as links.

This is really strange, at least from what I can tell looking at the video. It seems like something is moving together with the view and obstructs the light. You can also see it over the stairs in the background, the previous render had the light fall in from the top while in the video it is shadowed...

I'm not sure if this is the issue, but the light itself also has a shadow setting that often times people aren't aware of called "shadow" and "contact shadow" make sure both of them are on. Then try adjusting the contact shadow "distance" amount and see if it helps.

Yes I thought so too. But the only settings available for the light source are the ones shown under the previous post "settings for the main light source". Even if I change it to a point or spot light, the settings stay exactly the same. Maybe it is a change in 3.0 that I am not aware of, that moved those settings to another place.

@metacontent The Shadow options like Contact Shadows are only available in Eevee.  Although not stated in the question, the short video looks like he's using Cycles.

Yes I am sorry for not having menshioned that, but you are right. This is cycles


text:
Make leaves head to branch direction (sapling addon)
I am trying to generate something with the sapling addon where the leaves (custom object from the screne in my case) are looking at the direction of the end of a branch. Seems what ever I try they are rotating all over the place.
I tried to play with the rotation of the leaves etc but I cannot make it work.
Here I marked with the arrows how those leaf objects should be directed.

In this one it is mentioned that the 3D cursor rotation set to 0 solved the problem but I already have that set to 0:
Blender sapling mesh leaves rotation
Is this even possible with the sapling addon? Or are there any other good addons which can do this?

Hello, I have a relevant answer here - https://blender.stackexchange.com/a/241663/110840

To make this process easier, consider generating a tree with less geometry, hand-making a few branches with correct UVs and distributing those with a particle system first.  Apply that system and then separate those to another object for your final leaf particle system.

Two ways, 1st sapling generator itself includes leaves objects but I am not sure if you can use custom object for it. Another way with object like yours that is not way too complicated, you can go and select 1 vert at the end of every branch, make vertex group and assign those vertices into that group
Now go to particles settings, set Density to your vertex group and don't forget you need these two settings as well: (they are visible only if you check Advanced

Now you can end up with something like this what is exactly what you want (I used only some random object, you will use your leaves.

In the sapling leaves settings I selected the DupliVerts and I could select my custom leaf object, that is how I created that above. It is just that I could not make it so the leaf direction is pointing where the branch is pointing. Before you selected the verts at the end of the branch did you convert the sapling curve to a mesh?

yes you have to convert it into mesh in order to use particle settings

Okay, and did you make any specific changes when selecting your object as a custom object? I went to Render -> Render As: Object, and selected my custom object in the Instance Object but it won't display it. If I change it back to path it displays the paths.

@MikoCG personally whenever I used sapling I wasn't happy with their leaves, but maybe I could make it work nowadays


text:
Mesh disappearing when symmetrize it
everyone, I'm a beginner in Blender and 3d modeling, I was following a tutorial where I had to symmetrize the mesh. when I change the direction to +X to -X my mesh disappears but when i try out other directions they work, except for the one i mentioned. I would appreciate your help because i am stuck right now. Thanks in advance.

Symmetrize will use the object origin as the center of the symmetry, if the origin is shifted from the object center, here is what it will give:

So make sure that the origin is at the right position (you can right click in Object mode > Set Origin > Origin to Geometry). Also make sure that the local orientation is the one you want as the symmetry will take the local orientation into account, not the global one.

Thanks alot, it worked when i set the origin to geometry. it turns out the origin was not at the right position.


text:
How do I create a solid base for a 3D Google Maps Capture?
A while back a found this blog post about loading data from google maps, and I was hooked! I followed the tutorial and I've been successful in getting the data into blender, but the resulting 3D mesh is very crude.  It's not flat on the bottom, but hollow.

As my end goal is to 3D print this, do any of you know how to create a solid base for this mesh? (also any advice for cleaning up the "non-manifoldness" of the map)
I've uploaded the .blend file here.
All suggestions appreciated! Thanks!
(P.S. Bonus points for figuring out where it is.)

you could try this:
go in edit mode and side view of your model:

Select a good amount of bottom vertices with box select and x-ray mode on:

now press E to extrude and Z Z (yes two times to extrude in z direction)

now add a box which is just a big as you want and it should only include the vertices you just extruded like this:

give it a boolean modifier type union and you got your base:

Thanks for the answer! I did try it, and it returned "modifier returned error, skipping apply"

Then please make a video what you did or a step by step explanation so that I can help you


text:
Windows generated blend file compatibility with Ubuntu OS
I created a character in windows os. My college is trying to open that very same file in ubuntu but blender keeps crashing. Anybody knows why!? I thought Blender files were compatible across platforms…
We are both using Blender 2.82
Thanks!

Hi peat. Blender files are supposed to be compatible across platforms. However, Blender 2.82 is still in Alpha! So two things may have happened: 1) you encountered a bug in an alpha version, which is to be expected ("They can be unstable and mess up your files"); or 2) you don't have the exact same version: check the git hash that appears in the splash screen

You are right, they are different version:
windows: 502f01cc47ab
Linux: e0cd5b980fc5
I had everything automatically packed into .blend, etc, etc but didn't realize about the different versions (just saw that both were 2.82 and thought that was enough).
I've got a character rigged and ready to use. I need to use ubuntu. What would be the best option!? At this point I can only see myself doing everything from scratch in ubuntu. Is there any other options!?

I don't know honestly, it's trial and error from here. Unless you receive better answers, I'd start by trying: 1) opening the file on Ubuntu with 2.81. If it opens correctly, save it: you're now on a stable track. If it fails, 2) in Blender 2.81, in a empty file, append the scene or the object from your file. If it fails 3) open your b2.82, select and copy the object; open Blender 2.81 and paste it. In any case, your goal is to bring everything back to a stable version.

If you're having compatibility issues and loading the files crashes Blender, please report this on the bug tracker with the affected Blender version (in this case the Ubuntu version) and the .blend file that causes issues. The bug reporting can be started from Blender through Help > Report a Bug or by clicking here.

Robert Gützkow something interesting is going on right now. I've been trying blender 2.82 and 2.81 for Linux and they both crash every time I try viewport shading (material and render preview). This is not file related, it happens even when no file is loaded. As soon as you click in one of those, blender crashes.
With regards to my file, I'm now allow to open one of the version I did in windows in Blender 2.81 for Linux but I cannot save it and I cannot viewport shading (material and render preview). I'll try 2.8 for Linux and see what happens!

Thanks Nicola Sap! Looks like I'll have to start from scratch! Blender in Ubuntu is a bit unstable! I'll have to find a version that actually works in Ubuntu because 2.81 and 2.82 don't! I'll try 2.80!

I always use the latest version of Blender with Ubuntu 16.04 and 18.04 and all works very well 99% of the time. It looks like your system has some peculiar problems. It would be great if you could file bug reports for the weird behaviour you're seeing!

That's what I don't understand! I've got ubuntu 18.04 and I have try blender 2.80, 2.81 and 2.82. Viewport shading (material and render preview) doesn't work in any of those! Even when I'm not working in any of my files! Blender just crash! At this point I'm not sure if it's blender or something on my side...

@peat Sounds like an issue with your graphics driver or hardware not meeting the minimum requirements for Blender 2.8x. Please update you graphics driver and check if your the minimum requirements are fulfilled (especially the GPU requirements).

@Robert Gützkow in windows blender works fine. Drivers are up to date and I'm above minimum requirements! I'm only having these problems in Linux. So far I've try ubuntu and manjaro and the results are the same! That's why I'm so confuse! To me it doesn't make sense!

That's why you should ensure that the drivers are up-to-date on Linux and that the hardware meets the minimum requirements. How exactly are you testing this on Linux? Is it on the same hardware with dual boot, a VM or a different computer?

@Robert Gützkow same computer with dual boot. I haven't try a VM yet


text:
I can't install opencv in the python 3.7.4 that blender uses
I'm trying to install opencv libraries (imutils, numpy, dlib, etc). My blender version is 2.8.2 and it uses the self contain python (3.7.4).
After updating Manjaro, there's a Python 3.8.1 also installed! and this is where all the problems begin!
When I try to install opencv in blender' python it says that everything is already install and up to date pointing to python 3.8.1! and doesn't let me do the installation in python 3.7.4.
The problem is, when I run my scripts in blender I got an error message because some files are missing (imutils for example: No module named 'imutils') and looks like the error points to the python installed within blender.
So how can I force the installation of these elements in the python within blender!?
Is there any other solution!? perhaps forcing blender to use the python in the OS?
Not sure if my hypothesis about the error is right, but at this point it is my best guest...
Please find below the console message:
Read prefs: /home/manjaro/.config/blender/2.82/config/userpref.blend
found bundled python: /home/manjaro/Descargas/blender-2.82-e0cd5b980fc5-linux-glibc217-x86_64/2.82/python
Read blend: /home/manjaro/Descargas/blender-2.82-e0cd5b980fc5-linux-glibc217-x86_64/carpeta trabajo blender 2.82/vincent_modify/Vincent to be modify6b83.blend
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_up_4_bbone_easeout_R"].rotation_quaternion[1]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_low_4_bbone_easeout_R"].rotation_quaternion[1]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_up_4_bbone_easeout_R"].rotation_quaternion[2]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_up_4_bbone_easeout_R"].rotation_quaternion[3]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_low_4_bbone_easeout_R"].rotation_quaternion[2]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_up_4_bbone_easeout_L"].rotation_quaternion[1]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_low_4_bbone_easeout_L"].rotation_quaternion[1]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_low_4_bbone_easeout_R"].rotation_quaternion[3]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_low_4_bbone_easeout_L"].rotation_quaternion[2]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_low_4_bbone_easeout_L"].rotation_quaternion[3]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_up_4_bbone_easeout_L"].rotation_quaternion[2]
ERROR (bke.anim_sys): /home/sources/buildbot-x86_64-slave/linux_glibc217_x86_64_cmake/blender.git/source/blender/blenkernel/intern/anim_sys.c:4160 BKE_animsys_eval_driver: invalid driver - pose.bones["lip_up_4_bbone_easeout_L"].rotation_quaternion[3]
Traceback (most recent call last):
  File "/home/manjaro/Descargas/blender-2.82-e0cd5b980fc5-linux-glibc217-x86_64/carpeta trabajo blender 2.82/vincent_modify/Vincent to be modify6b83.blend/OpenCVAnimOperator", line 2, in <module>
ModuleNotFoundError: No module named 'imutils'
Error: Python script failed, check the message in the system console

Manjaro 18.1.4
Blender 2.82
Python 3.7.4 (in blender) and 3.8.1 (in the OS)
Thanks!

Blender has it's own API so you can't change it's version of python sadly.

Yohello 1 I know, but there should be a way to downgrade os python to match the one in blender, or a way to install what I need in blender' python...Maybe I can set PYTHONPATH to to an external Python (the same version that uses blender though)...I don't know, that's why I'm asking! but there should be a solution...

How exactly did you try to install the package in Blender?

@Robert Gützkow

The problem is everytime I tried I got a message saying that everything is installed and up to date pointing to python in the OS

Well you need to issue the commands for Blender's Python, since python3 is the alias for the python 3.8.1 installed on your system (and not for Blender's Python). Navigate to the directory where you've installed Blender and open ./2.82/python/bin. Run the commands using ./python -m pip install [...]

@Robert Gützkow
that's what I did (I should have been more specific). The problem is that once I navigate to ./2.82/python/bin, I can't use ./python because it doesn't exist. My only chance is using ./python3.7m.
So now I did:
./python3.7m -m ensurepip
Successfully installed pip-19.0.3 setuptools-40.8.0
./python3.7m -m pip install --upgrade pip --user
Successfully installed pip-19.3.1
You are using pip version 19.0.3, however version 19.3.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
I don't understand this...

@Robert Gützkow
./python3.7m -m pip install opencv-python opencv-contrib-python imutils numpy dlib --user
Installing collected packages: numpy, opencv-python, opencv-contrib-python, imutils, dlib
Running setup.py install for imutils ... done
Running setup.py install for dlib ... error
ERROR: Command errored out with exit status 1:
and got a huge error

@Robert Gützkow
not sure where to go from there. It looks like it doesn't matter what I do I'll end up having pretty much the same errors. I could try and install cmake and try to install again dlib. The last time I tried to do that I did:
pip install cmake
Successfully installed cmake-3.15.3

and then I did:
./python3.7m -m pip install opencv-python opencv-contrib-python imutils numpy dlib --user
Requirement already satisfied: opencv-python in /home/manjaro/.local/lib/python3.7/site-packages (4.1.2.30)
Requirement already satisfied: opencv-contrib-python in /home/manjaro/.local/lib/python3.7/site-packages (4.1.2.30)
Requirement already satisfied: imutils in /home/manjaro/.local/lib/python3.7/site-packages (0.5.3)
Requirement already satisfied: numpy in /home/manjaro/.local/lib/python3.7/site-packages (1.18.0)

Collecting dlib
Using cached https://files.pythonhosted.org/packages/63/92/05c3b98636661cb80d190a5a777dd94effcc14c0f6893222e5ca81e74fbc/dlib-19.19.0.tar.gz
Installing collected packages: dlib
Running setup.py install for dlib ... error
and got again the very same error

Looks like only dlib failed to install (not sure why without seeing the error message). BTW you don't need ensurepip, Blender ships with pip already installed

Let us continue this discussion in chat.


text:
Freestyle svg exporting long paths that extend way out of the rendering area
I have a wireframe I'm attempting to export from blender -> svg in inkscape -> pen plotter, but I can't find a way to "crop" or cut the wireframe so that it's bounded within the render.
Inkscape screenshot
Blender screenshot
I've attempted to crop them in inkscape, but unfortunately the normal cropping workflow just hides the cropped portion of the paths, and my pen plotter still attempts to draw them. So I was wondering if there was an easy way to do it in blender without mangling my scene. (so that I can export different views of it easily)

How to upload an image to a post

I chose to leave them as links because they were large and made the post kind of ugly


text:
View clip an object permanently
I want to clip an object with view clipping as a solution to this svg export problem, but when I render the view clipped object as an svg, I still get the unclipped version of the svg. So I was wondering if there's a way to permanently view clip the object, and maybe create a new scene with just that clipped object that I can then render.

I think the best solution is to go in edit mode of the path. select the part that you only want to show, and separate it into its own object by pressing [P]
Alternatively you can try to use a Boolean modifier with intersect to non destructively cut down an object.
you might also try using culling with objects during render time: Culling Objects Using a Culling Object


text:
Attributing "active" type to object during animation
An object is suspended above a plane. Halfway the animation I want it to suddenly become an "active" body, so that it drops down under the influence of gravity, ending with bouncing on the plane.
However, apparently it is impossible to keyframe "type" (under the Rigid Body tab). In this case it would need to change from "passive" to "active".
Any solutions?

Keyframe up to ... then Animate the "Animated" switch... or change the start frame of the rigid body world.  Sure there is a similar (or same) answer. See https://blender.stackexchange.com/questions/81106/i-need-to-delay-the-rigid-body-on-a-cell-fractured-object-how


text:
F key not working
I am watching this tutorial, https://www.youtube.com/watch?v=f1sjHg4KtyY, and I'm at this part of it, https://youtu.be/f1sjHg4KtyY?t=762, but I dont understand what they do, and when I press F, nothing happens.

The F key is to fill a face or create an edge from the selected vertices. This is the section in the Blender manual explaining what you can do with it.

The F key is used to fill a face. You need to have enough vertices selected to create a face, this usually works by having the vertices surround a particular empty space. If you want to fill only part of it, you can extrude an edge from a vertex by pressing E and then merging it to another vertex by pressing M.


text:
Rotating bone constrained by "child of" has rotational error
I have a simple two-bone rig. One bone has the constraint "child of" pointing to the other bone. Both bones are identical, in the same spot, with all axes pointing in the same direction. They are set to Euler ZYX.
I have the "child of" constraint's influence set to 0.5, so it follows with a lag.
I rotate around the parent bone around the X axis a full 360deg.
The issue: when the parent reaches 180deg, the child bone suddenly flips to point towards its negative Y axis.
I've tried turning off everything except "rotation x" in the constraint settings, but the results are even worse - the location of the child bone suddenly drops along the negative Z.
Any ideas what could be going on? Can attach the Blend file if I find a way.

I don't know if it's fixable, but you could try with drivers. To share the file: blend-exchange.com

Thanks, have uploaded the file here:

Why Euler? I think Quaternions are supposed to fix exactly this problem.

You could try with drivers. In Pose mode, select the "parent" bone and right click on the X rotation value in the N panel > Copy as New Driver:

Then select the "child" bone and in the N panel right click on the X rotation value and Paste Driver. The value should now be pink:

Then right click again on the same value and Edit Driver, it will open a pop-up window, in this window choose Type > Scripted Expression and in Expression type Rotation Euler/2:

Hi, thanks for this! It is less the rig I am trying to build and more that I am trying to understand the basics of how bones work - so I am wondering what's going on mathematically that would make the bones do this, for greater understanding when I build more complex rigs (if weird stuff is already happening with just two bones, then...)


text:
Using alpha textures with particles
I have a particle system set to render as object.
The object has an image texture that is a white dot that fades to black. This texture is also the alpha channel.
The alpha matte works fine on the original object, i.e. it fades to nothing around the edges.
However, when this same object appears in the particle system, I don't get any transparency at all. It fades to black instead of to transparent.
Any reason the particles might be doing this?

Would you mind give us more information, like which render engine you use, how is the material setup, the particle system settings etc. and show us some screenshots? Because the only thing I get from this is you have an object with some alpha transparency but using it as particle makes it opaque. If I recreate this in some way, it works as expected with transparency. So we need a lot more details to see what you did differently, or even better load up your file here: https://blend-exchange.com/ and follow the instructions there to edit it into your question.

Answering my own question! It turned out this was the fix: https://blender.stackexchange.com/questions/253028/

Thanks Gordon Brinkmann! I should have mentioned I am using Cycles and the latest version of Blender 3.4.1. The fix turned out to be changing the Transparent number in the Cycles settings to match the number of particle.


text:
Can I make tools in blender which opens as a separate window?
Rather than my tools attached to either sidebar or properties i want just a panel which consists of all the tools and then once i click on the name of the tool , it open separately in a different smaller window.Is there any way to achieve this ?

It's not possible as is with BPY, but there's this addon that implements it:
Floating Windows - Coding / Released Scripts and Themes - Blender Artists Community
It works on Windows only. But you can either use it as is, or look at the code to make your own.


text:
Mantaflow Smoke big and chunky
I am following along with this tutorial
https://www.youtube.com/watch?v=t4S6xSLKHoY&t=375s
Once he gets to the explosion effect part I start having issues. For some reason my smoke is big and chunky. I would like to slim them down and make them less square. I know I can increase the resolution divisions, but the tutorial guy is able to get a decent effect with only 128 divisions. Also my smoke does not show up in a render.

you should NOT always believe what you see in yt. I made yt tutorials myself and i just can tell: almost every video uploaded is cut, changed and improved in any thinkable way. And yes, of course, i do it too - because you don't wanna hear someone cough or throat... ;)

I can see that. He makes it look so quick and smooth with all the editing.


text:
How to control edge wear for only certain edges?
I'm following along with this tutorial https://www.youtube.com/watch?v=NnlaIizA_AQ&t=552s
He uses nodes to get the edge wear effect, but how do I achieve more control over this? Such as edge wearing only certain edges.
Is there a way to use vertex groups instead of a shader that auto detects edges? Or use the bevel shader and use a vertex group to control the influence.

I guess painting a b&w mask will be the best. There are some other ways like Ambiant Occlusion or Pointiness but you  won't get as much control as with an image texture

Just create two materials.
As with all materials you can select the vertices on your object where you want to put your material on and the hit "assign".

result:

That's going to create some hard transitions. I would like to have one edge worn and then fade out  towards the adjacent edges.


text:
Adjusting the pitch of an audio clip also adjusts the speed
When I raise and lower the pitch of an audio clip it also increases/decreases the speed of the sound. I just want to adjust the pitch and not the length. Is there a way to do this?

Not in blender 2.93- . The pitch control is just a regular speed control. Also, the effect is time-relative to the beginning of the strip, so playing from the middle will not sound the same as playing from the beginning. That is a known limitation. However, you can use an external program such as Audacity to create such effects. With the FFmpeg library set up in Audacity’s preferences, you can even import audio straight from video files within Audacity.

Do you know if newer versions of blender can do this now?

@AMixOfGeekStuff I just tested it, and the speed control has been removed altogether. I still recommend Audacity, which has thankfully improved quite a bit since I posted the answer. However, you seem pretty specific in wanting this particular functionality in Blender itself. What are you wanting to use it for? Maybe there's a workaround.

Honestly just convenience. Itd be easier to only use blender instead of having to switch to audacity, with its different controls for zooming and panning, and then I have to export it to my PC and then find it on my PC and drag the file to blender.

You can bookmark the locations in both applications, you know.


text:
Does blender have a simple particle system method for smoke, etc?
I know about blenders mantaflow smoke simulation, but I'm looking for a more simpler way to do it like how Unity 3D's particle system works, or Lightwaves.
Its basically just particles with sprites attached to them, with no actual smoke calculations. I'm very new to blenders particle system in general, so if someone could point me in the right direction that would be great. All the info I can find about doing smoke in blender points to the mantaflow system.

https://www.youtube.com/watch?v=hx8m9w4YyNo
This might hold the answers you seek

There are many ways to fake smoke without doing a smoke simulation.  https://youtu.be/tL0G5oOjdtk is one of the better youtube tutorials on how to do it with a particle system.  A second approach is to use textures as in this tutorial: https://youtu.be/okcQkF0uN-M  There's also the sprite 'billboard' approach: https://youtu.be/hx8m9w4YyNo as mentioned by @NascentSpace


text:
How to properly rig a hip control?
In most rigging tutorials they setup the bones like this. But there's no way to swing the hips properly without special "control" bones.

Why not place the bone like this?

This makes sense to me, but every professional tutorial I find does it like the first image. Even the built in rigify metarigs are like that. There must be something I'm missing. Is it wrong anatomy?

In any advanced rig, what matters is what the control bones offer. And a good rig will always give you MULTIPLE options for such things, different parents, orientation, spaces and so on... So that the animator is the one deciding how he wants to perform. Deform bones don't have to be in any specific hierarchy nor orientation, you could literally have all deform bones parented to the root and oriented in world coordinates, it would still work. Actually, some rigs are made this way.

Either way you're showing is fine.  The weights are the same, and all you're doing is changing the center of rotation of the root.
But control bones aren't special, and for most riggers, they're not really optional either.  So these tutorials are showing you how to place deforming bones, expecting you to create control bones as well.
It is very useful to have a bone at the center of gravity of models.  This is the point about which models will, mostly, rotate.  If we swing our hips, we're rotating about our center of gravity.  But the center of gravity isn't at the level of either end of your spine0.  Spine0's position was chosen for its effects on autoweights, not for its relation to what people's bodies rotate about.  Neither end is the right center of rotation. After this first step, of getting good deforming bones and good weights for them, we might make a non-deforming Center bone, and then parent spine0 to it:

Once we have that, it doesn't matter whether spine0 points up or down, because we're not rotating spine0 anyways, we're rotating CoG.
If we do that, are there any reasons to prefer spine0 pointing towards, rather than away from, spine1?  Yes, if we want to set up bendy bones for our spine, or if we want to use IK (spline or regular), the orientation shown is easier to set up.  Otherwise?  No, it really doesn't matter.
However, you should absolutely feel free to create your rig however you'd like!  There is no right answer about hierarchy questions like these.  Different designs support different animations and different animators, that's all.  Tutorials are showing you one way to build an armature, which is a good first way, a good way to get started, but you're fully expected to go your own way afterwards as you get a feel for how you like to rig and for how you (or your team) like to animate.

Because it was root bone, like control center for armature. If you flip it the upper bone will be root done instead which is really hard to work with.

Rotate default Human(Meta-Rig) around X axis.

Rotate your design around X axis.

To achieve the same result have to select all bone or go back to Object Mode. Imaging, if you want animate your character to jump and flip, especially when you want to export it to game engine, this is nightmare.


text:
Export Bendy bone squishy deformation?
I read that bendy bones cant be exported to other software, in my case Unity 3D. So people say you have to convert bendy bones to regular bones, then export it. Although i'm wondering if the "squishy" deformation you get with bendy bones able to be exported as well? In other words, the mesh deformation when you move bendy bones closer or further away, that is controlled with the volume settings in the stretch to modifier,

Strech to modifier simply acts on scaling the bone, so yes, it's exportable: in pose mode select all deforming bones, go to pose menu > animation > bake action, turn on all preferences, and bake. Then you can delete all non deforming bones and export a simple rig without modifiers with ease.


text:
Add a simple bone pivot to Rigify rig
I'm in the process of learning rigify and I want to add a simple jaw bone for the mouth, but I don't know how to make a handle for that when generating a rigify rig.
I tried to modify a meta rig (i think its the wolf rig). But it never generates a usable control for the jaw bone. I've attached the blend file.
https://drive.google.com/file/d/1d0Z9MyEa8P2ITISrP-2pJeiC5NbMUiNZ/view?usp=sharing

You can add everything from rigify samples. Not sure that exactly you need to add, but I think you can test and select what it more suitable for your needs.

I cant find the rigify samples dropdown. I clicked on a rig but its not there.

@Mike have you searched in edit mode?

looks like this tab has been renamed to Rigify buttons. I still cant figure it out though. When I add a basic.pivot bone, generate rig, and apply automatic weights it doesn't move the jaw.


text:
Rig shoes composed of multiple parts
I am relatively new too blender and finished a model i want to animate now.
The rig is working (i used rigify) and i managed to rig/parent the clothing as well (pants/tshirt).
But i am struggling to find a way to rig the shoes so they can deform with the rig, as the are composed of multiple objetcs (rivtes, laces, mesh etc)
I tried to join all the objects before parenting with auto weight and it still does not work.
The differents object behave independently (see screenshot)
I tried the data transfer method and nothing moves.
Whats would be the ideal worflow to achieve this?
Thanks in advance.

look this! will help you
https://youtu.be/1WS8b1Ww8Ys
if your model has a foot attached to the rest of the body ... you can do the same procedure, and use the data transfer on the deformation object

great solution using a mesh deform modfier!

actually, what do you mean by "if a foot is attached...". I do a have a foot attached to my body model and I sometimes run into a situation where the rig's deformation causes my foot to look through the shoe, because mesh deformation on the shoe and armature deformation around the foot area are quite different probably... do you have a solution to this?


text:
[Blender 2.8]Why autosave do not save edit-mode data, and how can I auto save them?
In Blender 2.8, autosave said that edit-mode data won't be saved, and I just noticed this after an hour's work lost.
So any way to force Blender to save data in edit-mode when autosaving?


text:
Trying to smooth edges with normal map
I recently started using Blender and made my first character model, after that, I retopologized the model to make it low-poly for games. Now I want to smooth polygon edges of my low-poly model and so I found out that I can fake smooth edges with normal maps. I've baked the normal map from the high poly model but the edges on the low-poly model are still sharp.

High-poly:

Low-poly:

Normal map:

Low-poly with normal map:

What am I doing wrong?

Can you share your node group please?

I think your low poly mesh does not have smooth shading enabled. You can enable it again by selecting your low-poly mesh, then pressing W -> Shade Smooth or going to Object -> Shade Smooth.

Yeah, I know but how do I "shade smooth" in other software, for example in a game engine? I thought this "smooth" info is stored in the normal map.

Oh i get it, this 'shade smooth' info is stored in the fbx file. Haha, so stupid. :D


text:
Math in Texture Nodes
I’m having trouble figuring out how a math node influences a texture node. Say you have the Musgrave Texture node and put the output into an add node. Does the node add all the values within the texture node such as Scale, Detail, Dimension, etc?

The output of a Musgrave texture is, for each pixel of the texture, a value between 0 (black) and 1 (white). If you plug that into a Add node, you add that value with the second value of the Add node :


text:
Generate random segments
I would like to have a guide to generate segments of length l distributed randomly without intersection in a defined square field. The end of the loop is fixed by the total length of the right generated. Grateful if someone could help me.

A quick hack is to run a rigid body simulation until you arrive at a frame which looks right. Writing a script to get what you need can be a bit of a puzzle...


text:
The animation of the tank’s caterpillars, when you go through the animation, the caterpillars collapse, why?
I decided to make an animation of the tank’s tracks, the model of the tank is complex and the tracks are also complex. After a large number of attempts to set up the correct physics, nothing happens and everything collapses when the animation starts.

Honestly I think you would get into less trouble by using drivers rather than using a simulation, you can find plenty of resources on the subject on YT

What kind of technique will be much more difficult to implement than animation of physics? Yes, but there are videos in which a similar technique is realized and the tank really goes. Or did they also use this technique in the form of drivers?


text:
Can I render an image along the X axis - so it's completely flat? or not
I'm an interior design student and wanted a section of what my room would look like from the side image, and was wondering if I could get a rendered section from completely the side (x-axis) or do I have to use the camera function and not get it completely to the side? ]1
Many thanks!

Select the camera and click the camera tab of the Properties Window.
Then under lens change the type from perspective to orthographic and adjust the orthographic scale to fit your scene.
Now you can press N  to adjust the location and rotation.
These settings should get you where you want to be:

Location: (10, 0, 0)
Rotation: (90, 0, 90)

You can switch between views by pressing 1, 3 or 7 on numpad for Front, Righ and Top views (hold ctrl for Back, Left and Bottom).
Press 5 to switch between orthographic and perspective views.
To align camera (active one) with current view press ctrl + alt + 0 on numpad.
If you don't have a numpad, you can mark "emulate numpad" option in preferences.


text:
Python 2.8: principled BSDF get linked base color
I an trying to capture all possible values of the base color slot of the Principled BSDF. I have found ways to get the default color or a linked texture slot of the Principled BSDF, but having trouble getting to get a linked color (for example when a RGB color node is hooked up as a link to the base color value).
context: I'm trying to optimize an exporter. Right now it has support for linked texture maps and default colors, but hooking up color nodes to the base color value is not supported.

Use InputSocket.is_linked and NodeLink.from_node attributes... If you don't use them how do you get/support linked texture maps?

Thanks for the reply. If I understand it correctly, using nodelink.from_node mean that I have to evaluate every possible condition of incoming node (rgb node, mix, color correction nodes ...).
I was wondering whether there's a more efficient way than check for every possible node that could be link to base color?

NL.from_node returns a reference of the connected node and I don't think there is another way to get the color...

Usually it's the first output of the node which gets connected to the color input of the bdsf, so you could do NodeLink.from_node().outputs[0].default_value to get the input color, since it will work wether the linked node is a RGB, color correction, etc.

Thanks for your help! Two more follow up questions: (1) how would you evaluate the datatype of NodeLink.from_node().outputs[0].default_value  (I'd need to know whether it's a simple color value or a map (for example a color correction node could be passing a single color or a color corrected map)   (2) If the data type is a map, does the python API provide a way to write a texture t the drive? In other words: how would you go about writing a color corrected map to the drive?

Or another way to put it: is there a way to detect whether there's a map linked to the base color slot (the map might be passed through a node like a color correction) and if so, is there a way to bake that incoming map?

Please edit your question instead @Schiette Also please add your current code to the question. And consider to ask only one question per post, read: https://blender.stackexchange.com/help/how-to-ask


text:
Why is my viewport performance (a lot) slower when using solid mode compared to rendered (eevee or cycles)?
When I use solid mode for my viewport Blender suddenly becomes very slow and laggy. I can still move the camera around or change stuff, but only with a lot of delay. When I switch rendered mode the lag disappears. This is the case for Eevee and Cycles, the former being quicker of course.
The lag also disappears if I use wireframe mode or solid mode + X-ray.
I am using a particle system with 5463 objects, so there are a lot of objects in the scene. But why is the solid mode slower than the rendered mode?

My hardware:
AMD Ryzen 7 3800X
32 GB RAM
GeForce RTX 2060 Super
Can anyone help me? Should I provide any further information?
Thank you!

If the said particle system is hair, you might have not set the same amount of rendered particles. Sorry, can't comment yet

I am the one who asked the question, but unfortunately I can not login with my old account. @lastgoodname: Thank you for your answer but the particle system is Emitter, not hair.


text:
White lines appearing when rendering shadows to separate layer and recombining in compositor
I have trawled forums for ages looking for a possible answer to this.
I am trying to render shadows to a separate layer then recombining them in the compositor with the rest of the image. This is because I would like to have complete control over the shadow layer and ultimately apply a mask to it (to avoid any shadows extending past the render border creating a hard edge).
I have created a simplified setup to demonstrate the issue.

In this simplified setup I have 2 view layers, layer 1 containing a cube and layer two containing a shadow catching plane. You can see that the lines appear at the border between the shadows and the object. I have looked into issues of premultiplied alpha but none of this seem to sort it. They appear despite the condition of either Convert Premul checkboxes on the Alpha Over nodes.
I suspect that it may be to to with the Transparency filter in the Film section of the properties, however altering this leads to poor results.
Does anyone have a solution or some tips on what to investigate. This will ultimately be for an animation and so I'm keen to achieve everything in Blender rather than saving 2 sets of frames for the shadows and for the objects
For reference here is an image of just the first view layer with both the cube and shadow cater being rendered showing no lines

Any help or advise would be massively appreciated

I did a test scene like the one you did.  I thought it was due to the premult setting (usually that's the guilty party for compositing edges), but that's not the case here.
 Part of it is due to anti-aliasing and the pixel filter - not because of bad settings, but just the nature of it.
With the cube by itself, the edges of the alpha are going white to black, with some grey in the middle.  For the shadow catcher and holdout cube, the edges between the shadow's alpha are going white to grey to black, in the opposite direction.  This edge is on the same pixels for both layers, of course. When you do an alpha over, that edge results in some grey alpha values from both layers competing for the same pixels.  Therefore, some of your white background peeks through and shows up as white
The best solution is, simply, don't composite this.  If you can avoid compositing layers of the same CG scene, render the shadow and object together.  My guess is you want to do this for visual effects; I do that too and run into this situation often.  I usually render the shadow together with any CG object I'm putting in a video to get a clean edge.
If you must composite them together, you can do some masking and simply expand the shadow layer's alpha edge with a dilate/erode node.  That can get messy and give strange results, but it's possible.

Great answer! if perhaps not the answer I'd hoped for. This makes a lot of sense. You are right I am doing this for VFX but also as I often need to render objects, complete with cast shadows onto completely white surfaces so that there is no visible 'seams' at the edges of the frame caused by tonal differences from slight shadow remaining on the floor.
I know there's ways to do this using masks and essentially white vignettes but it always struck me as a bit inflexible.

I have actually managed to achieve what I wanted by adapting some of the techniques used in this tutorial: https://www.youtube.com/watch?v=qgs5JGy2qIU&feature=youtu.be
It seems that the shadow catcher in blender is not very full featured and so its beneficial to essentially build your own approximation. The only issue I ran into was that it does add render calculations....


text:
geometry nodes > rotation of grid instances
The instances of a grid rotate wrongly.
I want a rotation only in the y direction but the rotation is done in the x and y direction.

I must be something essential that I'm doing wrong...
How do I pass on the distance value from the proximity node as a y vector value?
Thx!

A note in addition to @Chris' answer: Map Range->Separate XYZ casts a Float to a Vector, which will fill X,Y and Z of the vector with the same float. Then SeparateXYZ(Y)->Rotation does it again,. You could replace Separate XYZ with Combine XYZ .

try this node tree:

several things you should know:

Blender and GN are working internally with radians, not degrees. So if you want to rotate a half circle, the correct value is Pi, not 180 degrees.

the map range node of type float outputs a float. So it makes no sense to separate a float to xyz value.

you want to use the combine xyz value - which takes 3 floats and makes a vector out of them

Hint: you can enter "pi" in a value field - Blender knows it
Hint 2: you can enter "tau" in a value field - which is 2 * pi

This indeed solves my issue. Thanks Chris!

if my answer helped you, pls click on the checkmark left of my answer. thx


text:
how to limit the rotation of a rigid leg
I can't seem to limit the rotation of a rigged leg with IK.
I've added a Limit Rotation bone constraint but without success.
This is the first time i'm rigging something so I must miss a basic rules?
Do I apply the bone constraint to the control bone or the deform bone?
If the answer is deform bone, which one?
I also noticed that you can limit the movement in the Inverse Kinematics section of the Bone properties panel. Should I use this instead of the bone constraint?

https://drive.google.com/file/d/1-Lm_JsuIYkzYftWQEhozsVjVl0y7woUD/view?usp=sharing
Thanks for your help!

the constraints won't work along the IK chain, so, as you say, you need to use the the Limit XYZ in the Bone panel > Inverse Kinematics

I can put a constraint on the bones by using the Lock IK function but when I then use the control bone it's not working anymore ...
https://drive.google.com/file/d/1Hp1N-CGxG5Ve8KiB9WhKjp4Y_RN_HFDG/view?usp=sharing

Yes it's hard to handle, I'm a bit lost with these bone limits   :(

Actually the best way to control the leg os to use the pole target bone, for the moment it's a bit too close to the knee, what are you trying to achieve exactly, why do you want to use the limits?

OK so actually I think that the problem comes from the fact that the pole target prevent the limits to work properly, so I guess you either need to use the pole target (but place it correctly) or use limits


text:
Select all the faces with inverted normals
I desperatly need to clean up some geometry that was previously moddeled in a CAD software. Is there a way to automatically select all the red parts so I can filp them?
Recalculating normals does not work and selecting all the faces with "L" will take forever since this is not the only object I have to clean up.

Edit: Select Similar -> Normal also does not work

Edit Mode, with the whole mesh selected Recalculate the normals ( ctrl N ) that should fix the problem (from https://blender.stackexchange.com/a/12174/88382)

It is possible and likely that surfaces coming from CAD software are not continuous, so Recalculate Normals will not work alone in a lot of cases.

If you select all and merge vertices by distance (alt + m) to avoid separate faces, you can then use Recalculate Normals function (shift + n outside, or shift + ctrl + n inside). If that does not work, it means there is simply no way for the algorithms to determine what the right direction might be - if for example you had a few separate planes in random orientations in the mesh of the object, there would be no way to determine what you want to consider the right direction for normals or even what would be consistent for all of the separate planes for your situation without you specifying that. In that case you need to manually select them and set the normals as you like.

Sadly, merging the verts messes up the geometry. Its strange that there is no way to just select all the red faces since blender has already marked them.

It kind of depends on your end goal. What are you looking to do with the model?
Merging vertexes in some cases can help but this requires your model to have somewhat clean topology which CAD software is highly unlikely to generate.
I'd first recommend checking the model's scale. Then try merging vertexes with a really small merge distance. Lastly you can try to recalculate the normals.

In the case that merging+recalculating normals is not working and in the spirit of providing what OP asked for, I have written a script that will select all the red faces for you.
import bpy
import bmesh

print("=================")

# Set to object mode.
bpy.ops.object.mode_set(mode = 'OBJECT')

# Get the active object
obj = bpy.context.active_object

faces=[]
if obj and obj.type == 'MESH':
    mesh = bpy.context.active_object
    # Get selected faces
    selected_faces = [f.index for f in mesh.data.polygons if f.select]

    # Loop through the selected faces.
    for face_index in selected_faces:
        face = mesh.data.polygons[face_index]
        normal = face.normal

        # Get location of the current 3d view.
        area = next(area for area in bpy.context.window.screen.areas if area.type == 'VIEW_3D')
        view_location = area.spaces.active.region_3d.view_matrix.inverted().translation

        # modify the view location so that it is at (0,0,0) and calculate
        # the dot product with the normal.
        dot_product = normal.dot(view_location - face.center)

        # If the dot product is negative then this is a 'red' face.
        if dot_product < 0:
            faces.append(face_index)

    # Deselect all faces
    bpy.ops.object.mode_set(mode = 'EDIT')
    bpy.ops.mesh.select_all(action = 'DESELECT')
    bpy.ops.object.mode_set(mode = 'OBJECT')

    # Reselect only the inverted faces.
    for face in faces:
        obj.data.polygons[face].select = True

    bpy.ops.object.mode_set(mode = 'EDIT')

else:
    print("No valid mesh object in edit mode found.")

In Face Select mode, select all the faces you want to filter from and then run the script. Only the red faces will be left selected, allowing you to easily flip them. Make sure that your 3D view position is not changed between when you select the faces and run the script, as this position is used in the calculation.

The best solution I have found is:

Merge Verts
Recalculate Outside
Subdivision Surface to fix broken Geometry


text:
Bunched / Wrapped Cable
Im very new to Blender and was wondering if there is a way to model a wrapped cable that is held together in the middle (by a velcro Strap).
Like this:

Thank you in advance!

The question is tagged modeling and is pretty big, and I'm not going to make a full-blown tutorial (I wouldn't be able, and is off-topic), so I'm focusing on the basics, trying to get to a decent starting point and ignoring the modeling of details and the shading.
The starting point is simply a curve. Start by adding a Bezier curve.
In Edit mode (Tab), select one of the two default handles and:

E extrude it to the opposite side, making sure to add some variation/randomness
repeat for several loops

rotate the handles in the view you've been using (select, R, repeat) to add randomness, or to align them (it really depends on how messy you want the cable)
change view and add some random displacement of the handles in the perpendicular direction (select, G, repeat)

You now want to add handles along the middle in order to control the shrinking. To do so:

select all your handles (A)
right click, Subdivide

Deselect all the vertices (AA) and select only the middle ones using a box select (B)
Shrink these handles along all axes except the long one, in my example: the X axis (S, shiftX)

The curve is done, now it requires some thickness.

Exit Edit mode (Tab), go to the Curve properties, and under Geometry, increase the Bevel > Depth.

You will probably see some overlaps, that can be fixed by moving some handles manually in edit mode.
The velcro strap can be done starting from a plane and extruding it around the middle: while doing it, look around often to check that it's not intersecting or staying too far from the wires. With a Subdivision Surface modifier, it will then look softer

Thank you so much! And I am sorry if I made any tagging mistakes!

You didn't make tagging mistakes! I meant: since you are interested in modeling, I'll focus on the modeling in my answer.


text:
Blender closes/crashes everytime I open and close a window
Since yesterday blender constantly closes/crashes everytime I open and close a window.
So far this happens on every window I have tried (e.g. file output path, file import, viewport windows, image textures)

Better image quality: https://i.sstatic.net/sf3gp.jpg
So far I have:
Restarted the pc multiple times
Reinstalled Blender multiple times (via steam and manually)
Deleted all the Blender related files in Appdata and program files
Without any luck.
Hopefully one of you can help me.
Best wishes!

The guys over at blender told me what the issue was.
Turns out the problem is caused by my wacom drawing tablet. I uninstalled the drivers and now its working fine again!
Hope this helps someone!


text:
How to add scrollbar in my nested panel and add delete button?
So i have created this custom panel (thanks to people from this community who helps me out tho )which shows list of objects based on the category i have selected from the dropdown ,i want the list in a separate box should i do it using nested panel or UILayout , also rather than it just being a list of objects I want to be able to select the objects from the list and a delete button in the bottom which will help me delete the selected object from the list.

It's not possible

@Karan any alternate approach to get a similar result ?


text:
Distribute pointed objects on a curved surface with random orientation and constraint
I am trying to put objects with random orientations on a curved surface, however the orientations must be limited to directions pointing away from the surface, thereby, avoiding clipping the surface. The objects will be later specified to be very simple molecules with a spheric head and a zig-zag tail. In the example you see here, I just stacked two cones on each other.
I have managed to distribute the objects using Distribute Points on Faces. I also know how to individually give the objects random rotations with Random Value->Vector and connecting the node to  the Rotation socket of Instance on Points.

From my understanding the generated random vector(s) use the local coordinate system of my surface object as their basis, i.e., the same coordinate system for each generated random vector. Although I can for example limit the z-rotation from 0 to pi, this does not take into account, that the surface is curved and will result in clipping.
I have started using blender a couple of days ago, so there are still a lot of things I do not understand, such as when the RNG node generates one vector for all distributed objects and when it generates a random vector for each distributed object.
Also, this is all only for a still, I do not intend to do any animations.
Thank you in advance and best regards,
WiseKouichi

It seems like the Normal socket is not very useful or I do not understand it well enough.

The Normal socket is giving you the direction of the face the point was generated on. It's just a vector though, raw data; it doesn't yet have any relation to your objects. Might be a clumsy metaphor, but think of it like this: you are in a dark room and want to face the sun. You ask Blender which direction (Normal) the sun is. It says "Sun is towards East (Vector: 1,0,0)". Trouble is, since you're in a dark room you don't know which direction you're facing. If you're facing North, for example, to face the sun you need to turn 90° clockwise. If you're facing West, you need to turn 180°, and so on... That relationship between your current direction and the sun's, the instruction that tells you how much you should turn and which way so you can align yourself with the sun, is your Rotation.
In this particular case you're lucky because you're using a Distribute Points on Faces node and it takes care of the job of calculating the alignment and gives you the Rotation directly. What if you were not using a node that gives you Rotation though? You simply instanced some objects on the vertices of a mesh directly, for instance. Then, you would need to do the alignment yourself, most of the time by using Align Euler to Vector:

To apply that in your example, you could rotate the Normal vector(s) randomly between positive and negative 90°, and then align your instances to the result(s):

when the RNG node generates one vector for all distributed objects and when it generates a random vector for each distributed object

There are two general types of sockets you'll see in Geometry Nodes. Some are circular, and some are diamond-shaped. Circular ones give you a singular data that doesn't change with the context. When it's diamond shaped, however, the data gets calculated for each element in a domain individually. These are called "fields". The "context" is basically the first main branch of the geometry (green sockets and links) the node is linked to. You can read more about it on the Blender manual.

Thank you very much for the informative answer. I had a feeling I was lucky with the Rotation socket. In Vector Rotate a fixed rotation axis is specified, is it not? In your case, the Normals are rotated around (1,1,1). If I vary the seed I can see a bias towards the  (1,1,1) direction. I am not sure if that is the case in your implementation as well. Can you clarify that?

I got it! It seems like the Normal socket is not very useful or I do not understand it well enough. When I use that socket and scale it up, the distributed objects point all over the place. One should simply use the Rotation socket along with Rotate Euler->Local

I tested the range of values for the RNG node by using a vector node. Here, the local z-axis points in the direction of the surface normals. The local y-axis points along the slope of the surface and the x-axis coincides with the world-y-axis. In this case I allow a very limited range for the local x-rotation. Allow 180° rotation around local y and full rotation along local z.
Here is the result:


text:
Possible problems with lower version blender rendering higher version models
I mainly use 2.83 in my work, but when I use it to render some models, there are always some messy errors. I want to ask what changes blender has made after 2.83 that make it impossible to render with 2.83, and what errors may occur when I use 2.83 to render higher version models.

If I understand you correctly you are trying to render a blender file made in a higher version like 3.x using 2.8x blender.  The options used in 3.x may have improved or changed.  Try the version it was created in and see if the problem still occurs.

it is pretty "natural" that older versions of software (not just Blender) cannot work with "things" made in newer versions - with the exception that it might work if you only use features which are implemented in the older version, but even then - it is not guaranteed to work so you shouldn't just do it if you wanna be safe. E.g. if you are using a geometry node which doesn't exist in the old version - what should the "old" Blender do? it just doesn't know it! Think of cars. Let's assume BMW replaces the engine with an electric engine. You can still transport people in both cars. But you ...

...cannot use electricity to charge your old car. And by the way: the fact that you cannot charge is not an error...

...and to add to what @Chris said, you didn't even tell us which "higher version" you mean. There have been many versions since 2.83 up to now, do you expect a list of every feature that has been implemented since then that might or might not make problems with rendering? And for all possible scenes? I mean, there not only was the change from Cycles to Cycles X, but even other things... a default cube with a default material and a point light might be less problematic to render in old versions then complex  materials, rigid bodies, cloth, smoke, water simulations...


text:
How to show expected remaining render time
When rendering animation, the info in the top-left corner of the render window shows the time per rendered frame. Is there a way to also have the expected remaining render time for the whole animation showing?

Similarly to https://blender.stackexchange.com/questions/133114/is-it-possible-to-get-total-render-time-via-python-code  could estimate based on average time.

There is an add-on for this problem called Render Estimation

Blender does not have the function to show complete animation render time. Best option is average render time multiplied by remaining frames. It should be noted that render time changes according to what is visible on screen. Its actually quite hard to know ahead of time how much time is needed per frame and it can also be affected by other processes other than Blender running on the computer.

Lame it  doesn't have this natively. In Lightwave, it just shows you estimates based on render time up to then, you still have to mentally predict the LOD for upcoming frames, but waaaay better than trying to do math from flashing numbers. if only they just stayed on screen.

Pretty lame indeed. It's not that hard... wonder why they didn't do it. Found a plugin but it's $6


text:
Converting a mono audio strip to a stereo audio strip
I have imported an mp4 video file (an interview) into the VSE, for use with an animation. The audio of the video file is mono. I want the VSE to output a video file with the audio in stereo (so that the video is played on two speakers, not one, as is the case now). How can this be done?

In the Sidebar check mono.
Duplicate the audio Shift + D to a new channel.
In the Sidebar set Pan value to -1 in one audio strip and +1 in the other.


text:
Copying object without dope sheet data
How do I make a copy of an object without coying any of its dope sheet data? So the new object should have an empty dope sheet.

After copying, you can unlink the action fron the object, by turning the dopesheet into an action editor and pressing the X button near the action name to unlink it.


text:
How to lock the view to the XY, XZ, or YZ plane
When I'm in top, bottom or side view, I would like to lock the view to the 2 dimensions of the viewing plane (XY plane, XZ plane or YZ plane), so that - when working in that view - I don't accidentally turn the view into 3 dimensions. How can this be done?

Check this one out: https://blender.stackexchange.com/a/144411/35559

There's the Toggle Quad View option, which has such functionality.
It splits your viewport into multiple views, that cannot be rotated.
View > Area > Toggle Quad View
Shortcut: Ctrl + Alt + Q

Just visited this old answer from a year ago, and realized how it doesn't actually answer the question :)


text:
Setting scaling to 1, but keeping object size in meters
I open a new file in Blender, so I get the Cube. The edge lengths of the Cube are 2 meters. Now I change the scale factor from 1 to 2, so the edges grow to 4 meters.
Is there a way to set the scale factor to 1 again, while the edges maintain length 4 meters?
I need this feature to solve a problem with HDRI environment textures. My object is a car, and it is too small for the roads in the HDRI panorama. The proportions in meters of the car are correct, but it has a scale factor of 0.3. I suspect the scale factor has to be 1 for the meter size of the object to match correctly with the HDRI.

Ctrl + A then click Scale, this will reset your scale

Environment image (HDR or not) just mapped on infinite sphere.
The scale of you object (cube or car) not doesn't affect environment of depend on it.
Only for still camera you can adjust your model to environment using camera orientation and focal length.
https://i.sstatic.net/8OZre.jpg
Nonetheless to apply scale: select objects to be applied, go 3d Viewport menu > Object > Apply > Scale (or All Transforms)


text:
Defining materials for a whole scene (file)
I have the impression that materials are defined per object. Probably the reason why Blender keeps adding ".001" ".002" etc. to the material names. can anyone explain this automated nomenclature?
How can I set materials for a whole scene (in my case, a whole Blender file), so I can have a consistent list of material names (only set by me, not Blender) from which to choose for materializing objects?
Put differently: Is there a way of moving the material (creating) tab from the object-specific section (physics, constraints, particle etc.) to the scene-specific section (world, output, render, scene etc.)?

The materials can be re-used as often as you'd like. If the material isn't assigned to any object, then you probably want to add a fake user though, since otherwise it will be removed once you close Blender.

More succinctly, instead of creating a material each time, use the drop down to select one already in your blender project.

Materials are conceptually associated with users. In order for a material to be persistently stored it either needs to be assigned to an object (a real user) or the Fake User option needs to be enabled for it. If neither is the case, then the unused material won't be saved. That is the reason why you're always creating materials linked to an object when using the user interface.
However this doesn't mean that a material can only be used for one object. You can assign a material to as many objects as you like, across different view layers and scenes.

Creating a material
A material can be created in the Material Properties. You will need to select or create a new material slot, then you can create a new material using the New button.

Alternatively you can create a new material based on another material by clicking on the New Material icon shown below:

Reusing existing materials
Once you've created a material, it can be assigned to other objects. Select the object in the 3D view and choose a material from the dropdown list.

Users and fake users
Materials that are currently without any user will be marked with a zero in front of its name in the dropdown list. If you don't assign this material to an object or activate the fake user option (the shield icon marked in yellow), it won't be saved in your project.

If a material has multiple users, then a button with a number will appear. You can create a separate copy of the material for the currently active object by clicking on the button (marked in red).

More information can be found in the manual.

The shield looking icon when clicked creates a "fake user" which makes that material available in the file/scene even if it's not assigned to an object. The icon to the right of the shield will create a copy of the current material and automatically increment the name as it seems you're seeing with ".001".

Check out more on that here: https://docs.blender.org/manual/en/latest/render/materials/assignment.html


text:
Snapping to Play Head in the VSE
In the Video Sequence Editor, how can I make a strip selection snap to the Play Head (the vertical blue cursor line)?

Select strips.
Right click to open menu.
Select Snap to Playhead.


text:
Objects in entire project can no longer be edited
When I RMB-click on any object in my project, it no longer gets a yellow profile that indicates that it is selected. However, in the Scene panel on the right, it does appear in yellow. I can also perform transformations (move, rotate, scale) on the "selected" object.
However, when I go into Edit Mode (see picture), the view of the "selected" object doesn't change, whereas normally it should change to either a vertex, edge or face view. The Editing interface does appear, but since there are no vertices, edges or faces to select, it's useless.
Did I inadvertently lock or deactivate a functionality in Blender?

You've disabled overlays. Look at the button top right of the 3d view.

This is starting to become embarring. Thanks, again, @lemon

You have to activate Show Overlays.


text:
Rigging my model doesn't work
My model isn't responding at all when I parent it to the armature I have set up for it. It is clearly parented because it can move around but it does not move with the bones of the rig when I go into pose mode. Example gif below. Please help I'm so tired.

Please share your blend file. (How to add a blend file)

Look at the status bar. See the yellow warning for a few seconds? It's the infamous Heat weighting: failed to find solution for one or more bones error


text:
How can I create Knife animations in blender?
I have created a Game-Engine ready setup for exporting a selection of animations to Unity. I am currently in the process of creating, what is meant to be, CSGO style knife animations. Note that I am reasonably familiar with animation in blender (however I am only an intermediate)
My setup currently:

How should I start? I'd like to know (to begin) how to make just a basic idle, breathing animation. With the complicated structure of blender's set of specialized editors (the graph editor, dope sheet etc...) I find it difficult to know how to start, and after that make it feel immersive and natural. Also I'd like to know if there is more needed in my setup, for example my game is an fps, should I add a camera for a reference view?
If anyone can help me start creating these animations, and show me the steps involved for creating even a simple idle breathing animation using this setup. That'd be greatly appreciated
Thanks!

can you provide a link to a video how it should look like?

Would you like the Idle animation, or the whole set of animations I wish to create (or base off of)?

3:30-3:45 https://www.youtube.com/watch?v=s-oQT0zXPHU : This is closest to the style of animations I am looking for


text:
Strange divots on mesh located?
I was looking through this (https://www.youtube.com/watch?v=24hUk1Xjtog) speed model by blend motion, and it inspired me to create a similar combat style knife. In blend motion's video the blade had similar bumpy issues however they seemed to just fix themselves somehow, this was not the case for me.
With Subsurf:
Without Subsurf
However the blade has got strange divots on the serrated side of the blade, these divots create an unwanted bumpy look to the model.
Without Subsurf:
I have tried moving the inner and outer edges on the x and y axis; also scaling the sides on the Y axis by zero to try and flatten the edge, to try and stop this (this did nothing), I also experimented with the normal directions to see if that was the problem, though this did not fix anything.
Example of tipology's (without sub divisions)
Front:
Front(zoomed on to bump):
Serrated edge side:
Serrated edge side(zoomed):
I want to use this model for a game-engine but these bumpy parts of the mesh stick out like a saw thumb. Any help would be greatly appreciated. Thanks!

please share your file  https://blend-exchange.com/

 This is the .blend file

If you manage to fix this, a walkthrough of your workflow would be very helpful

Hi! Please follow these steps
STEP 1
I changed the lighting of the mesh to matcap and chose a charcoal black colour so we can spot the bad shading easily.Then I tweaked the geometry of a few faces by deleted them and reconstructing them.

STEP 2
Then I added and deleted some edge loops, added the subdivision surface modifier and then increased the levels of subdivision to 2.

Hope this worked :)
Final Result:

This worked like a charm. Thank you very much, this is a great help!

your welcome! happy to help :)


text:
How to make mesh move as one
I'm rigging a model to a new rig, and every time I parent it to the new rig the mesh of the model is fine.
That is until I move it and everything moves except the eyes which move in their own directions. I've been trying to solve this for a while now and can't figure it out.

Solved! I just forgot to apply the modifier.


text:
Texture not applying correctly in Blender
So, I'm new to Blender and I started to mess around with nodes. And I tried importing a face texture to my head model and it imported it quite weirdly.
Nodes:

Face Texture:

Blender View:

I am not good with texturing and nodes but a guess, its because you used it as and alpha. Just erase the alpha connection. You want to use it only as a image texture right?

If I understand your requirement correctly you want to map the face image onto one face of your object, and color the rest with a simple color where the image is transparent?
It can be done with simple UV Mapping, and using the Alpha channel to drive the mixing factor.


text:
Script to create individual plane with mapped texture for each image in directory
Sorry if the title is unclear, I couldn't think how else to word it.
What I'm looking to do is create a book with turning pages, where each page uses an image from a specified directory, so the ideal end output would create a plane for each item in the folder and assign the next image sequentially to that plane.
First question on here and not too familiar with Python, so any help/input would be much appreciated!
Thanks

The texture coordinates don’t actually need to be changed at all, just the materials. In fact, depending on what you’re doing, it might be more efficient to just run the same two-page animation over and over via an NLA strip, but have the material sequence through all the images one by one for each page turn (and one ahead for the page behind it).

Looping across the list of filenames using this answer to create individual planes like so;
import bpy
import os

def create_page(filename, page_num):
    bpy.ops.mesh.primitive_plane_add(size=2, enter_editmode=False, align='WORLD', location=(0, 0, 0), scale=(1, 1, 1))
    plane_object = bpy.context.view_layer.objects.active
    plane_object.name = f"page-{page_num}"

    page_material = bpy.data.materials.new(name='page-material-{page_number}')
    page_material.use_nodes = True

    principled_bsdf_node = page_material.node_tree.nodes["Principled BSDF"]
    image_texture_node = page_material.node_tree.nodes.new('ShaderNodeTexImage')
    image_texture_node.image = bpy.data.images.load(filename)

    page_material.node_tree.links.new(principled_bsdf_node.inputs['Base Color'], image_texture_node.outputs['Color'])

    # Assign it to object
    if plane_object.data.materials:
        plane_object.data.materials[0] = page_material
    else:
        plane_object.data.materials.append(page_material)

    material_output_node = page_material.node_tree.nodes.get('Material Output')

# Replace <SPECIFIED DIRECTORY> with location of image files
image_file_directory = <SPECIFIED DIRECTORY>
for page_num, image_file_name in enumerate(os.listdir(image_file_directory)):
    # It may be necessary to parse the filenames if there are files in the specified
    # directory which are not images or should be otherwise excluded
    create_page(image_file_name, page_num)


text:
Explosions and fireflies / dots in Blender 2.8 (already followed all tutorial without results)
Good morning everyone,
I'm literally ready to pay who will be able to solve my problem.
here is the original file of the explosion.
https://drive.google.com/file/d/1UBb2ctIG_OQ5qh7bpMSTUFcNI_E1LTCq/view?usp=sharing
Blender 2.8
Cycles

PROBLEM: FIREFLIES, STILL A LOT OF THEM IN RENDERING.
Everytime I use fire / explosion I cant get those fireflies away in the rendering.
Already followed all tutorials/discussions/youtubevideos about deleting fireflies in rendering.
Already tried everything without finding a solution (clamp, light size, hundreds of samples, caustics, filter glossy, glossy bounces, multiple importance).
The denoiser helps but it really makes a lot of damage to my scene, so I would want to try avoid it for now, and for sure this scene can get a lot better before I will put the denoiser as a last touch. But for sure for now there is still too much fireflies/dots!
Please open the original file and help me find a solution !!
It does that everytime I work with fire/explosions.
With smokes I can fix the problem, but when it comes to fire here they appear without solutions!
Thank you very much for helping

The only way to do this without denoising is increasing the number of samples up to about 2500. It takes a long time to render, but your image stays crisp.

please try to do it using my .blend file? Because I really have the suspect that those fireflies are not the ones that goes away when you use crazy amount of samples, but I dont know ..
Thanks for your reply in any case !!
[Ah, I dont have modern GTX graphic cards or similar that allows me to use 2500 samples in an explosion scene, would take 14 days for 1 frame, this is the reason why I ask you to try that please! xD ]

Use embergen to create flip book, composite in later. Fake the lighting from explosion in composite as well.


text:
Blender 2.81 Principled BSDF shader with sss not showing diffuse pass
When using the the principled BSDF shader with any amount of sss the diffuse passes are completely black. It seems the sss passes inherit the diffuse pass information. The node tree is just the shader and the output node.
If I turn the sss down to 0, the diffuse passes work again.
When instead using a regular diffuse shader, mixed with an sss shader, everything works as expected. Diffuse passes included.
Is this a known issue, intended behaviour of the Principled BSDF shader or just me doing something wrong?
I'm using Blender 2.81


text:
How do you control the speed of rotation?
Heyo, I've been using Blender for about a year now. I came from Maya and C4d. I have a problem that seems like it should have a simple answer, but I can't find it. How do you control the REVOLUTIONS of something rotating? When I try to set keys from 0 to 360 degrees, it works fine, but if I THEN add a 3rd key frame, so that the object slows down back to 0 degrees, from 360 degrees, the object starts to spin backwards halfway through the animation. I just want it to start spinning, get faster, and then slow down. What am i doing wrong? Is this something that con only done in the NLA? If so how?
Thanks in advance to anyone who can help.

Hit "N" to call the right side panel and type in directly the rotation what you want for example (0;0;720) then hover the mouse above the rotation panel and hit I to animate the rotation's value.

Thanks FFeller.  I got it to work, I had to add a keyframe at every second, each time adding 360 degrees in the positive.  Once I had that, i was then able to slow down the rotation by dragging out the final keyframe.  Thanks for your help anyway!

If you found solution please create an answer for your question and mark the answer as solved. Like now people searching for similar issue don't know it has solution. If you don't want to help others you can consider to delete your question if you don't see it as useful.


text:
How can i set a specific length for an edge?
I want to build a room with specific length. For example 40cm. So, i want to put a specific value somewhere. Answer only for Blender 2.8/ 2.81 pls. BTW sorry for my bad english

Related, but don't know if it works for 2.8: https://blender.stackexchange.com/questions/4890/how-to-set-a-specific-edge-length-numerically

I already tried that, but Edit Tools doesen't appear when im pressing w

Just to illustrate Ray's comment.
Enable ✓ the Mesh Tools addon.
Preferences > Addons > Edit Mesh Tools

Switch to Edit mode, to see the Mesh Tools addon.
It's under Sidebar > Edit > Mesh Tools


text:
How do I animate video windows?
I am looking to create a collage of 4 different windows all displaying their own individual video content simultaneously, each manifesting in the centre of the screen and then moving to one of four corners as the animation progresses. Is this possible in Blender? Thanks!

Blender can do that. You would use the Video Sequencer and Movie Clip Editor for that kind of stuff. Here is the documentation for those Editor screens: Video Sequencer | Movie Clip Editor

Thanks a lot PJM :D


text:
I have changed the rendering to the gpu but blender keeps doing it with the cpu
Hello as I said in the title, i changed the rendering to my gpu because is better than my cpu, but for some reason, when i open the task manager it turns out that blender is using 100% of the CPU and nothing of the GPU, I have already changed the options and I really don't know what happens, I am new using this. Attached image.

Have you enabled your GPU in the preferences (CUDA if Nvidia GPU or OpenCL if AMD GPU)?

Go to Preferences and go to System. At the top, it will show None, CUDA, and OpenCL. Toggle between until you see your GPU listed. If you don't see it, then your GPU is not compatible with Blender.


text:
Why are the faces skipped?
Blender 2.81a MacOS

I tried lifting the vertices and this is what I got.

I started modelling with a plane, got rid of the two vertices and formed this mesh, by extruding, subdividing and joining them.
I'd love to know where I got wrong so that I can model better in the future.

Your first gif clearly shows that the faces in the problematic area aren't connected to the vertices you're moving. This can be seen by the little square that is in the middle of every face.

The first gif shows that you have faces which aren't properly connected to the surrounding vertices. This can be seen because the face center is marked with a little black square.

The top face is an ngon that consists of eight vertices (marked in blue) and the center vertex isn't part of it.

In order to fix this, switch to face select mode (either by clicking on the icon or using the 3 shortcut in Blender 2.8x), select the top face and delete it (X > Faces).

Switch back to vertex select mode and select four vertices that are supposed to form a face. Press F to create a face and repeat this step with the next four vertices until you have created all four faces.

The two faces on the side are ngons as well and consist of six vertices each. The vertex you're moving in the second gif is part of both faces, but the two horizontal edges aren't.
Switch to face select mode and select both problematic faces. Then press X > Faces Only, which will remove the faces but keep the vertical edge.

Once the side faces are deleted, switch to vertex select mode, select four vertices and create a face with F. Repeat this step until you've created all four faces.


text:
How to achieve translucent pomegranate material?
Wanting to model a pomegranate kernel, I modelled two objects

The outer shell (red outer watery covering)
The seed (inner opaque whitish seed)

The seed

I want this to be opaque, but I don't want it's edge to have 100% opacity. I want it to blend with the outer shell more.
The outer shell

I played with IOR, transmission, alpha, subsurface scattering, roughness and specular.
I reached a point where I know what all these terms mean but I still am very indecisive to move forward. I feel there is something that I am doing wrong.

Desired result

Conclusion
I looked at various transparency node settings, tried using them but I am still not getting the fundamentals of nodes. How to use a particular node, how to decide which one to use over the other and how to cascade two or more nodes.
I am relatively new to CG, there are a lot of things that I am not aware of, nodes being one of them. Any sort of help or introduction to new concepts or link to articles/videos is welcomed.

Principled BSDF is a good all-in-one solution that covers most basic cases, but some times it is insufficient and you get better results and more fine grain control by by manually combining other nodes with a Mix Shader and some gradients

Which renderer are you planning to use? It looks as if Cycles volumetrics might have a place here

Let's think like a photographer.

Proper lighting is essential - white background, strong backlight, fitting HDRi
Shader - Principled BSDF will do (let's keep it simple)
Use post-processing - adjusting midtone contrast, color-corrections

Outer Seed shader:

Roughness - pretty low, it needs to reflect environment and not
obstruct transmission
Clearcoat - just an artistic choice, as the outer seed has a thin glossy skin
Transmission - full 1
IOR - 1.6
Trans. rougness - 0,1 to distort the light a bit more

Notes:
When going for proper realism you'd use Volumetrics, Subsurface scattering and some textures for a more organic look.
But all things considered, proper lighting is everything here :).


text:
What is the theory behind loops? How can I select the entire edge loop in this case?
I fail to develop an intuition when it comes to the working of loops in blender

Geometry created from manipulating a cube, all the faces are quads

All the inner loops are continuous,

in both the directions,

But look what happens when I select the outer loops

Can someone explain to me the logic behind this? Link to articles are highly welcomed.
(I select the edge loops using alt key + left click)
I am using Blender 2.81a on a macOS

Hello :). Those outer edges aren't actually loops. This answer by @Rekov explains it really well https://blender.stackexchange.com/a/167163/

May be too simplified of an explanation but loops can only continue when quad faces are found on the way. If Tri is found, then the loop algorithm cannot decide to go left or right whereas if quads are found, it continues following the same "quad path"

Got it!
It is so logical.


text:
Bevel won't go above certain size
Sorry if I've overlooked something simple but this is driving me crazy. I'm just trying to apply a bevel modifier - but there's a limit to how large I can make it.
Please see the image to see what I mean, paying particular attention to the width value of the modifier.

Disable the clamp overlap option. Clamp overlap prevents the bevelled edges from overlapping each other (typically an indication that you don't want to exceed that bevel width).
If you're dealing with bad artifacts after exceeding the clamp overlap limit, this is most likely due to bevelling of a very acute angle. Try using the weight or vertex group limit methods to only bevel other edges in that case.


text:
Can't Extrude Multiple Faces
I'm trying to extrude multiple faces of a cube at the same time but it seems to be locked to the z-axis. I'm relatively new to Blender and I've spent all evening trying to figure this out - it's driving me nuts. Even more annoying is I'm sure I've done this before with no problem, but now whenever I try to extend multiple faces it's locked to the z-axis. I even reset the factory defaults and it's still doing it. Please can someone tell me what have I overlooked?

Alt-E .. > Individual Faces?

Shift Spacebar > 0 ? @RobinBetts

Extrude tool is set to Region by default. Just set it to Extrude Individual:

Many thanks for the reply. I think I perhaps didn't explain myself very well - I already tried this but couldn't get it to work - no matter what I did the extrude was being constrained to the z-axis. I've just figured it out. I was pressing the E key after selecting Extrude Individual - instead of just clicking and dragging