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Why is the gloss not showing when i render the image?
I am following the Blender Guru donut tutorial and i use viewport shading so i can see the supposed rendering result.

It clearly shows gloss on the icing, but when i click 'render the image' the gloss is no longer there.

I tried to increase the power on the lamp but it didn't do anything to the gloss.
I also tried to swith my render engines from eevee to cycles but it didn't do anything either. Please tell me what i'm doing wrong.

Ok. I figured it out. In the material roughness there was a button "animate property" and it wasn't clicked. Now it's on and the model is rendering correctly.

Hello and welcome. Rather than take photos of your monitor post actual screenshots instead, see How to take a screenshot. Photos are harder to read because we have to look past external interferences (like reflections, smudges or Moiré patterns) and guess if we are looking at hardware issues such as a malfunctioning display or connections, a software level issue like driver malfunction or glitch, or actual artifacts or issues with the model itself.


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Wavefront C++ (.obj) importer produces more vertices when later exporting glTF than old Python Wavefront (.obj) importer
My workflow for producing glTF file involves importing my OBJ file into blender. Tweaking things then exporting it from blender as an glTF.
After import blender shows that the old python OBJ importer and the new C++ OBJ importer produce a mesh with exactly the same number of vertices/edges/polygons:

When I then export it as a glTF file the new import version's binary file is almost double in size and taking it into a viewer shows the vertex count is almost double for most primitives.

I'm guessing the issue is that the internal indexing or storage of the newly imported object causes a less efficient output with the glTF so for now I always have to use the legacy importer but this isn't ideal.
Can anyone suggest what might be different with the new importer to account for this, or what might be changed in the exporter to fix this?

There are no developers here, nor does anyone here have any association with the Blender Foundation. I suggest you report that as a bug via Blender's Help > Report a Bug menu.

tl;dr – the new importer might be handling normals or UVs differently than the old one, requiring more vertices to export to glTF (and to render in any graphics API). Try disabling export for any vertex attributes you don't need, particularly normals and UVs.

source: Stack Exchange

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

sort: votes


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UV Unwrap not scaling correctly
Upon smart UV wrapping a toolbox, this happens:

As you can see the UV map is stretched. This is problematic as the pixels need to be perfectly square.
Assistance would be much appreciated.

did you apply the scale with Ctrl+A > Scale ? otherwise share your blend file https://blend-exchange.com

Important: apply the scale in Object Mode, this is nothing to be done in Edit Mode.

Well as pointed out in the comments by @HarryMcKenzie, it's probably a scale problem. If the scale of your object is not (1, 1, 1) then your UVs are going to be streched when you unwrap it with Smart UV Project :

The simplest solution would be (if you don't want to readjust all the UV manually) to apply the scale and then reunwrap the object :

I would (strongly) suggest that you allways pay attention to the scale of your object when working with Blender or any other software for that matter and allways make sure your scale is at 1 unless you have a good reason. Scale value other than 1 can lead to other kinds of problem. And as Robbin Betts says :

Personally, I would go further, and suggest: 'Never scale in object mode, while modelling'. Half the questions on this forum would disappear. But I'm probably bossier than you. :)

I hope I helped.

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


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Particles are falling through Collision Object - Even with Size Deflect
I am trying to emulate wind blowing dust in a desert scene, and try as I might I cannot stop the particles falling through the emitter object (a simple terrain).

The particle emitter is set to "size deflect" as per this answer:
Particles fall through collision object
...and the solidify modifier also does not stop particles passing through the mesh.
Gravity is turned down for the dust particles to 0.1
The emitter has some damping and friction.
I checked the normals and they are pointing the right way, so the particles are should be being emitted along them which is roughly globally Z in direction - as it should be.
The size of the particle returned to its default size 0.05 as per another recommendation and the source object scaled up.

Is there ANY solution to this? Any other tips of hacks?

The problem is that the particles (depending on the velocity you give them and other parameters) are to a great part generated directly at the surface, not above. And when the emitter is also a collision object for the particles, a lot of them can or will be reflected below the face, the opposite side of what you want.
What I do in those cases is duplicating the emitter object and placing the second slightly above the first. The bottom one gets the collision, the top one the particle system (with Show Emitter disabled). This way I'm sure the particles are above the collision object and are not reflected below the surface.
Here for example a setup with a 10 × 10 m "dune surface". The emitter object (still visible) is at a height of 0.00 m, the collision object slightly below at -0.01 m:

And this is the result with particles and some wind and the emitter set to be invisible (there are just a few particles falling off to the side, that's because they are blown beyond the border of the surface). Sorry for the bad quality, the file size here is limited to 2 MB:

Thanks for this very useful response. I have done this in the past to try and get around the problem and it does not work. Also - technically the particles are given a velocity along the normal (which is pointing upwards) and so should be emitted before falling or being blown back against the geometry. My solution was to use a cube which I then switched off for rendering. It seems particles in blender cannot handle complex geometry in certain circumstances.

@DrIgnatiusCole You did what in the past, what I show in my answer? It works as you can see, depending on the particle size and the gap between upper and lower surface... About the normal velocity: the problem is not that they are falling or being blown back against the geometry. In the moment they are emitted they are directly on the geometry which has the collision and get repelled immediately. Depending on simulation steps and substeps some might not emit exactly at the surface but slightly above or below it, so all this might cause complications with the emitter being the collider.

@DrIgnatiusCole Additionally to what I mention about particles being emitted below the surface, as you can see in this answer to a different problem, they are not always generated on or above a surface: Hair particle system forming square gaps

I have tried this in the past and still found the particles breaking through - I think even reported it as a bug. However, trying it again now it worked well. The trick is instead of using vertex groups for the emission, duplicate the part of the mesh you want the particles to emit from and then hide emitter. Have the emitter just slightly above the surface for safety.

@DrIgnatiusCole You didn't mention vertex groups in the question ;) At least from my experience with hair I would have definitely advised against using vertex groups...

That's interesting - why not? How would you do it instead - particularly for hair? Do you do what I did and and duplicate the vertex's and separate them into their own mesh?


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Copy from Active not Avialable for RB Constraints
I forgot to set the rigid body constraints for a long chain to "hinge" and I want to copy the rigid body constraints from one empty to all the others. However Rigid Body > Copy from Active is greyed out...I can't perform the operation.
Does anyone know of a way to copy rigid body constraints to multiple empties?

why don't you just delete the empties, select all rigid bodies and then object -> rigid body connect -> and then choose these settings here: [1]: https://i.sstatic.net/49eZ9.png (chain by distance is important)

Did not know about that (thanks), but it doesn't work in any case, because the hinge is dependent on the Z axis. If you do that for a chain, then the chain links will pas through each other. To do it properly, you need align the Z axis with where the chain link will pivot. Once you have 2 links, then you can duplicate the chain and use shift-R to copy and all the constraints will link together properly. In the end, rather than being able to copy the settings to the constraints I just had to start again.

normally you should be able to select all links and rotate them all at once in the direction you need


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How to permanently apply control rig animation to armature?
I have an animation in Blender that was created using the Mixamo control rig over a mixamo armature. My understanding was that to export the animation you would select the armature (not the rig) and simply export via bvh or fbx. I've done this in the past with Kinnect motion capture and it worked perfectly. However, I can't it to work in this instance.
I've tried all possible animation exports - gtlf, dae, usd, none of them work.
I can't think what I'm doing wrong. The rig is on layer 1, and the armature on layer 2 (created by mixamo rig add-on). What "should" happen is control rig drives the armature and the armature's animation should export as an armature animation I could then retarget. Importing into a blend file I should get that armature automatically. I get an armature when I import but it is completely scrambled.
Does anyone know what the proper process is for consolidating a rig animation to an armature?

Partial Answer - The answer to this was that it DID in fact import in, only it included the control rig as bones and it imported at the wrong rotation. So what looked scrambled actually included the correct armature, all mixed up with the control rig.
I found a way to export the armature as an FBX which did not have the control rig, but it did have a few bones missing from the armature for some reason. I still have no solution to how to remove a control rig from an armature or bake a control rigs motion to the armature and then remove it for retargeting other armatures.


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Rigid Body does not Behave as Expected
I am trying to create a trapeze. I am using cloth simulation for the ropes and for the handle I am trying to use a combination of an armature to drive a swinging motion and rigid body physics for free swinging.
To do this;

I have the origin for handle at the swing point.
I use "child of" constraint to control the position of the handle, key framed to turn off when I want the handle to fall naturally.
I have a rigid body constraint between a passive object at the top where the trapeze swings from, and the handle.
I am animating the rigid body physics for the handle so that animation is turned off close to top part of the swing.

What I expect to happen is that when the animation is turned off, the handle is then controlled by the rigid body physics and it should fall from its position constrained by the rigid body constraint to fall naturally.
Nothing remotely like that is happening. I have tried several methods but nothing is working.
What am I missing? I include the blend file to try:

The problem was "I have the origin for handle at the swing point."
The rigid body constraint calculates from the origin point of the handle. So by having the origin point and the rigid body constraint at the same place was causing my problems. Once I moved the origin point to the handle, and gone through several crashes, I got the result I was expecting.


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Images not loading when from certain directories
Images in blender will not load if they are from certain folders. When I attempt to load an image from the downloads folder, it works without issue, but when I try the same from documents/BlenderModels/Vehicles/Headlamps/Headlamp-Textures, it fails to load, and shows as pink.

Is this some kind of Windows folder access permission problem? Maybe create a standalone folder elsewhere on your drive and save your textures there?

If you can navigate to your Blender program you can likely give it administrator privileges.
If on a Windows device, press the Windows key, or type to search in the bottom left.
Search for "Blender." Right click the Blender version of choice (if multiple are installed) and press 'open file location.' Often a shortcut appears here, so right click it again and press 'open file location' (2nd from the top). On blender.exe (AND blender-launcher.exe if blender.exe doesn't solve it), right click it and choose properties. Go to the Security tab, click edit, and press the checkbox for 'Full control' under "Allow." Then click apply, then ok, then ok to finish the dialogue boxes. If you are the only user on your device this should solve the problem, save for other softwares interfering with Blender's permissions.

[Fixed] I also uninstalled and reinstalled blender.


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Mesh will not seamlessly UV unwrap
I've tried modifying the seams and changing the unwrap settings, but no matter what I do when I hit "smart UV Unwrap" the mesh will not unwrap seamlessly. Is there a way to fix this?

Smart UV Project doesn't take the seams into account, it will unwrap according to the angle defined in the Operator Box, if you want the seams to be taken into account, use the first option (called simply "Unwrap")? Or please explain more in detail what you want to do and maybe share your file

@moonboots I'm trying to apply the texture seamlessly to the mesh. Here's the file: https://drive.google.com/file/d/1GjSqRAGZplTFX8_8tkak-jL_ZjPP4jBU/view?usp=sharing

You have inner faces, remove them and unwrap again, now the texture should be seamless.
For such an object you could also try the Object output of the Texture Coordinate and set the Image Texture to Box instead of Flat, it will project the texture on the 3 axis.


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How can i display the Exact Same Colors that are in the Texture
I would like to render an animated prism, i made a texture with a different color for each face and some text. I want it to render it with no lighting, just the exact same texture, pixel to pixel as a transparent png sequence. They are simple bright folors like FF00FF and FF000. I just want it to be as flat as possible, with the exact same pixel values as the texture. Thanks

Just connect your image texture directly to the material output without using a shader first. In the image below, the cube on the left is connected directly, and the one on the right is connected through a Principled BSDF with default settings. The light is directly between them.

Color management settings should probably also be considered.


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Screw Modifier Texture
I am trying to use a screw modifier to make a screw that's textured like a basketball, can someone teach me how to do this? I don't understand how one edits texture on a screw modifier material without baking the mesh first, and I can't do that because i intend to animate the parameters on the modifier after texturing.
How do i do this? Thanks!

To texture a screw modifier without applying and unwrapping, use "Generated" as a texture co-ordinate. If you want more control over it's placement, use a mapping node between the Texture Coordinate and the Image Texture (not shown).

thank you so much!


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Material & Colours Look Different in Viewport Material Preview & Rendered Modes
newbie here... taking advantage of my covid lockdown to learn realistic 3D modelling. I'm doing the Youtube intro series done by Blender Guru, where you create a donut and a coffee mug and having a blast.
Problem: My donut icing and sprinkles no longer render right. In the Material Preview view, they both look as intended (white icing with a pink gloss, colorful sprinkles randomized), but in Rendered mode and after I've done a full render the sprinkles lose their random colour and the icing changes colour too (ends up a flat blue with the original colors of my spinkles that I made for the particle effect).
When I completed the donut, it rendered fine. Somewhere along the line in creating my coffee mug I've done something that has impacted the way the donut renders.
Attempted Solutions:

I've tried to redo the shading view options and recreate the randomized colors
I've deleted the lighting and put in new lighting (my understanding is that lighting is one of the major differences between Rendered and Material Preview
I've googled for solutions but haven't found anything of note to try.

Here is the blender file: https://www.dropbox.com/s/uuacijw1dts6xbo/Coffee%20Mug%20%26%20Donut.blend?dl=0
Any ideas on what I need to do to get my icing looking all nice and glossy pink and my random coloured sprinkles working in my render?
Thanks!
LEFT: Rendered mode (Colors are all wrong)           RIGHT: Material Preview (DESIRED LOOK!)

Shading View settings for Sprinkles

Shading View settings for Icing

It caused by the SubSurfaceScattering. Do you really need it?

The subsurface scattering gives my white icing a bit of a pink color. Similar effects on the sprinkles, but less visible.

If the subsurface scattering is rendering properly in the Material Preview viewport mode, why isn't it rendering properly in the Rendered viewport more?

Turns out it was the subsurface radius was too high...

Material Preview is not properly, because it's not affected by the lights.

thanks for the question, same i needed to look this up


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Capture Attribute and Transfer Attribute nodes
1. What is the difference between Capture Attribute and Transfer Attribute nodes?
2. How do different mapping modes in Transfer Attribute node work (Index, Nearest Face Interpolated, Nearest)?
3. What is an index here, and how this parameter affects Transfer Attribute node?

I try to give a very simplified description or an explanation that is as short and understandable as possible:
First of all: An attribute can be many things. Basically it is mostly a certain numerical value of a certain type.

Capture Attribute
Stores certain values for later use in the selected geometry. The data type of the value (Float, Vector, Integer, etc.) and to which part of the geometry it refers (Points, Edges, Faces, etc.) is defined.

Transfer Attributes
Fetches the values of a specific element or area from a geometry/object. Here, another object is queried, so to speak, and data can be transferred in this way, as the name suggests.
It is specified either whether a certain index of an element is to be queried here, or whether simply the nearest element of the specified domain (Points, Edges, Faces, etc.) is queried (Nearest). In case of Nearest Face Interpolated anything in between will be returned.

Index
Index is always a specific element of a domain (Points, Edges, Faces, etc.). In the case of a cube, for example, you have eight elements of type Points, and six elements of type Faces.

Official Documentation:

Capture Attribute
Transfer Attribute

It is not easy to put something complicated into simple words, so please forgive me if this presentation looks incomplete or amateurish.

It's fine. Anyway, can you be more specific with the mapping types? I don't seem to get it. And are there examples of using indexes?

I tried to make this description as concise as possible and break it down to the essential points. I think for more detailed (and better) explanations the documentation is certainly more precise. Many examples of how to use indexes can be found here on blender.stackexchange.com. I would recommend to just click through the website and the variety of questions/answers, because there are so many use cases.

I am asking questions here because I don't understand Manual explanation sometimes.

Yes, I absolutely understand that. But please mind: I can't condense all relevant things about this topic into a few lines for you in such a way that they cover all possibilities and are understandable for a beginner at the same time. Maybe you expect a little bit much from me/us, because if it would be that easy, the people from Blender would have written their own documentation that way. So please forgive me for only having the opportunity (and time) here to refer to the multitude of wonderful entries on this website.


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Object Selection: Select More/Less
I don't understand how Select ‣ More/Less ‣ Less operator works.
On the manual it says this,

Contrast the selection, deselect objects at the boundaries of parent/child relationships.

But this is vague and unintuitive. Would you mind providing more concrete explanation?
By the way, do you use these operators often?

If you select an object, you can quickly select its children or parent with Select More (shortcut Ctrl + and - to select less)

There are more implications because 'Select Less' isn't doing the polar opposite of 'Select More'

Il looks like Select Less will deselect, from parent to children

@moonboots It's kinda weird.

It works really weird ... https://imgur.com/qnDbDrs ... and order selection doesn't make a difference.


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How to select a material or object using the cryptomate node if it is a volume
I have a cube in the scene that I have assigned a volumetric material to. Why can't I select it using the cryptomate node when composing a scene? All materials and objects in the scene are displayed, except for those that contain volumetric material.

(Blender 3.6.1)

The docs say they are not supported.  My advice is to duplicate to a new layer, render an emission pass with your texture as emission input and use that as a mask in the compositor

@AllenSimpson can you show me an example please?


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The object continues to receive light from the turned off (through the light linking) light source
If you add an object to the light linking and turn it off, it stops receiving light from the turned off object, but receives it (light) as reflected rays from another object. Is there any way to turn this off with the light linking, or do I have to resort to some shading trickery? Any option will suit me.

 (Blender v 4.1.1)


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Why are my NLA editor clips grey and inactive?
I've been using the NLA editor to compose an animation scene using character rigs.
It'd been going great until I opened the file and found the clips are all grey and the rig is no longer animated at all.
I can't figure out why the clips are grey and inactive?
This has happened once before, but only to a single clip among many other working clips. I fixed it by moving the greyed-out clip onto a fresh NLA track and it immediately became active again. No such luck this time.
I've attached two images below - One of a working editor and one when it's seemingly broken.
I know that for many people, the NLA editor is still quite a mysterious tool in Blender, so I hope somebody here has some experience with this issue.
Thanks in advance for any help.

can u provide an example blend file pls? e.g. delete all actions except 2, if the problem still persists?

I have the answer to this problem now, so I will explain in detail below for anyone else who needs to know.
Basically, it was a glitch caused when I created a new clip on a track above the other, but then deleted said clip.
There are three solutions to essentially ‘refresh’ your NLA clips. One of them should work.

Select the foundational clip (on the track at the bottom of the
stack), take it into edit mode (tab key) and bring it back out
again. That should refresh all the tracks and clips above it and
essentially reactivate them.

Select the grayed-out clip, take it into edit mode (tab key), go
into the graph edit (for said clip) and make sure all the curves
(trans, rot, scale) are switched on (visibility). To do this, select
all the curves, hold ALT and press P.

As a last resort, select on the track that has a grey-out clip on
it, go to Add (in the NLA Editor) and select Add Tracks Above
Selected. Next, select your clip, press G (to translate), press Y
(to lock to the Y axis) and move your clip up to the newly created
track.

I hope that helps.


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In-Between Target function for Shape Keys?
It would greatly improve Blender’s character rigging (and animation) capabilities if the Shape Keys tool is updated with an In-Between Target function (see existing example from Maya below).
In-Between Target function for Shape Keys - Video
Currently our best option is to work-around the missing function using New Shape From Mix supported by carefully ordered driver keys.
Does anyone have any better solutions for this?
Thank you
Gary

In response to my question on Right Click Select, Asian3D made me aware of this Add On by NevilArt
https://www.youtube.com/watch?v=De3fiWcQnpA&t=44s
https://github.com/NevilArt/BsMax
It’s an extremely useful solution for my blinks challenge and hopefully will inspire the Blender Gods into implementing something in their future releases.


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Can you optimize Armature performance in Blender?
My scene contains one character model from Street Fighter V, and I get around 5fps. It's strange, since I can easily run that actual game at 60fps, but I suppose there are reasons Blender would be more demanding.
I noticed that removing the Armature modifier results in perfect performance, easily above 24fps. Yet, some googling led me to a post on the Blender forums claiming Armatures have minimal impact on scene performance.
This makes me think Armatures shouldn't be so demanding, and that my particular Armature is causing issues. Are there 'best practices' regarding Armature optimization?

In the game, all Armature movements (poses) have been baked - live previewing an Armature, editing an armature, posing, all that stuff, are not baked, and so they require a huge amount of calculations to the mesh for each bone. It's not about Blender specifically, it's just that the animations are pre-baked and require no calculations in-game. This is standard practice, there's no 3D software/computer that can do live armature calculations at 60fps.
(With a simple armature and a really nice computer, you might be able to, but that's an exception, not a rule)

I should add, with the new GPU Subdivision, you should get a lot better performance


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Offset a repeating image texture position
I am modeling a kitchen. Is there a way to offset an image that is repeating on the floor in the x-axis so that it looks more tiled?

AFAIK the only way is to edit the UV map. PS: you don’t need the Combine XYZ node, you can just enter the values straight into the Mapping node.

Thank you! Yes, the Combine XYZ is from a different test I was doing and forgot to remove it from the screenshot. I was attempting to add Maths to the x-coordinate, but that wasn't doing anything.

I wish I had seen this post earlier. I imagine you have either found a solution, or moved on from this project, but I have a tutorial on how to do exactly what you're looking for:
https://youtu.be/wFpcqbSmSs4
It's part 9 of an ongoing series. I hope you find it useful.

brick texture works to some extent, but not that good,the best way is to make a new texture.

Thank you! Yes, it's looking a different texture would work best.


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Geometry Node : Instancing a Grease Pencil Animation but at different times
Let's say I have made an FX of a single droplet of water in a Grease Pencil object.
I want to be able to achieve this :

But I don't want to do it the way I did it (copying & pasting & manually placing + offseting each grease pencil object in the scene and the timeline)
I would like to do it procedurally so I've used Geometry nodes to make this :

Almost there ! I could manage to randomize the scale, position and rotation but I can't seem to find a way to randomize the time of instance of the GP: They all play at the same time !
Is there a way to solve this ?
This would be really useful to quickly setup all sorts of FX

Have you tried the Time Offset modifier ?

I've been using it to offset the timing of the different FXs but I still had to  "manually"  go on each GP Object to change values for the modifier. :)

AFAIK this is not possible right now with "just" GN.
But...(although i am sure you don't wanna hear it or already know it) you can copy your grease pencil animation and offset your animation for each copy and make a collection of these objects and plug this into your point instance node.

Ay, at least I know I just can't do it that way. Thank you for your reply and your suggestion. ;)


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What is the best way of adding Kitbash 3d asset packs to the asset browser?
All of the individual assets are parented to an empty. When I mark it as an asset it looks like this:

I would like to add all of the emptys as individual entries in the asset browser.

At the moment, Asset Browser still lacks the functionality to use object groups(Collections) as assets. As this functionality is essential it would be reasonable to expect it added in the future and it is in the goals as we can see here: https://developer.blender.org/T94031
So at the moment full functionality needed for what you want is simply not there. You could use Python to make collections out objects parented to the empties and then make instances of those collections that can be made into assets, however it seems that you would need to somehow generate thumbnails as well.


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Turn instances into bounding boxes or proxies in the viewport
I am currently doing a large scale scene involving scattering tons of trees. The viewport slows to a crawl then I do so, is their a way to convert the meshes into bounding boxes when in the viewport but when it is rendered it renders the full res model?

Use is viewport and switch nodes like this:


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Is there any way to convert an empty with objects parented to it into a collection
I just got a Kitbash 3d asset pack and I want to add it to the blender asset browser but the problem with this is that the asset browser does not support objects parented to empties. is their a way to convert these to collections?

I just solved the same problem. Please, try this code:
"""Convert EMPTY to COLLECTION for selected objects or whole the scene. Recursively."""

import bpy

class ConvertEmptyToCollectionOperator(bpy.types.Operator):
    bl_idname = "wm.empty_to_collection"
    bl_label = "Minimal Operator"

    def execute(self, context):
        if len(bpy.context.selected_objects):
            objects = bpy.context.selected_objects
        else:
            objects = get_scene_children()
        for o in objects:
            if len(o.users_collection):
                parent_collection = o.users_collection[0]
            else:
                parent_collection = bpy.context.scene.collection
            self.empties_to_collections(o, parent_collection)
        return {'FINISHED'}

    def empties_to_collections(self, o, parent_collection):
        children = get_objects_children(o)
        if hasattr(o, 'type') and o.type == 'EMPTY':
            # Create a new collection
            new_collection = bpy.data.collections.new(o.name)
            parent_collection.children.link(new_collection)

            # Move all children into the collection
            for ch in o.children_recursive:
                for old_collection in ch.users_collection:
                    old_collection.objects.unlink(ch)
                new_collection.objects.link(ch)

            bpy.data.objects.remove(o)
            for ch in children:
                self.empties_to_collections(ch, new_collection)
        else:
            for ch in children:
                self.my_execute(ch, parent_collection)

def get_objects_children(obj):
    obs = []
    if hasattr(obj, 'children'):
        obs.extend(obj.children)
    if hasattr(obj, 'objects'):
        obs.extend(obj.objects)
    return obs

def get_scene_children():
    """List of the 'Scene' collection's children."""
    children = []
    for o in bpy.data.objects:
        if hasattr(o, 'parent') and o.parent is None:
            children.append(o)
    return children

bpy.utils.register_class(ConvertEmptyToCollectionOperator)

# run operator.
bpy.ops.wm.empty_to_collection()

Result is:

Duuuuuudeeee. Nice.

You will have to do it the manual way for now:
In the layer view right click the empty and click select hierarchy. Press M > new collection > name collection > shift + a > collection instance > select named collection > place origin on the newly made instance > make a 3d asset from the instance.
Someone should make an add-on to automate this process...

Unfortunately this is what I was trying to avoid.

just write a python script. easy :) i see alkor has one already.

This script should find all empties in the scene, create a new collection for each empty with the same name as the empty, and then move the empty and its child objects to the new collection while keeping them parented.
To use the script, open Blender and go to the Scripting workspace. Create a new text file and paste the code into it. Then, click the "Run Script" button or press F5 to execute the script.
The script:
import bpy

# Find all empties in the scene
empties = [obj for obj in bpy.context.scene.objects if obj.type ==
'EMPTY']

# Create a collection for each empty and move the empty and its
child objects to the collection
for empty in empties:
# Create a new collection with the same name as the empty
collection = bpy.data.collections.new(empty.name)
# Link the new collection to the scene
bpy.context.scene.collection.children.link(collection)

# Move the empty to the new collection
empty_collection = empty.users_collection[0]
empty_collection.objects.unlink(empty)
collection.objects.link(empty)

# Loop through all child objects of the empty
for obj in empty.children:
    # Move the object to the new collection
    obj_collection = obj.users_collection[0]
    obj_collection.objects.unlink(obj)
    collection.objects.link(obj)

# Select the original collection so that it's active
bpy.context.view_layer.active_layer_collection =
bpy.context.view_layer.layer_collection


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Stuck in wireframe

Using blender for the first time, and was just messing around with buttons, I think I clicked one of the physics simulation buttons, and now I'm stuck in this wireframe view. I don't want to make this geometry again (I've given up multiple times) Help?

Nvm, realised that the texture was removed, so it defaulted to wireframe

go to object properties - > viewport visibility -> change from wire to solid or texured


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bpy.ops.particle.brush_edit gives ERROR: poll() failed, context incorrect?. If I change the sceene it crashed blender without an error
bpy.ops.object.particle_system_add()
bpy.data.particles[-1].type = 'HAIR'
bpy.data.particles[-1].count = 0
bpy.ops.particle.particle_edit_toggle()
bpy.context.scene.tool_settings.particle_edit.brush.count = 1

area = bpy.context.area
old_type = area.type
area.type = 'VIEW_3D'
bpy.ops.particle.brush_edit(stroke=[{"name":"", "location":(0, 0, 0), "mouse":(374, 316), "pressure":0, "size":0, "pen_flip":False, "time":0, "is_start":False}])
area.type = old_type
```

if you comment the line before last line which is
bpy.ops.particle.brush_edit(stroke=[{"name":"", "location":(0, 0, 0), "mouse":(374, 316), "pressure":0, "size":0, "pen_flip":False, "time":0, "is_start":False}])
you can see the error

If you think that's a bug, please file a bug report. Main menu > Help > Report a bug.

It is already a reported bug from 2015 on another website about blender, alas they did not fix it; it says we "should not use" functions that mouse is required or similiar

Again, this website is a Q&A site and not the right place to report a bug. To get the ball rolling: it seems to work in Blender 2.8x: https://pastebin.com/qNCRWKqm Remaining issue is that poll() fails for brush_edit() (you have to pass the correct context members), Further reading: https://blender.stackexchange.com/questions/6101/poll-failed-context-incorrect-example-bpy-ops-view3d-background-image-add


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[obj.keyframe_insert, bpy.data.particles["ParticleSettings"].lifetime]; how to insert keyframe to an existed particle setting, e.g lifetime
I am trying to randomize some values of selected objects in blender
How can I keyframe_instert of the active particle properties?
I can do it with clicking "I" of the desired area and it works (creates a keyframe)
I tried: (n
obj = bpy.context.active_object
obj.keyframe_insert(data_path='bpy.data.particles["ParticleSettings"].lifetime')
obj.keyframe_insert(data_path="lifetime")

gave type errors both
TypeError: bpy_struct.keyframe_insert() property "lifetime" not found

Set on the object that has the property
Python console code.  A default particle system has been added to a Plane that has context.
The lifetime is set to 10 and keyframed on frame 1.
>>> C.object
bpy.data.objects['Plane']

>>> ps = C.object.particle_systems['ParticleSettings'].settings
>>> ps
bpy.data.particles['ParticleSettings']

>>> ps.lifetime
10.0

>>> ps.keyframe_insert("lifetime", frame=1)
True

Notice the objects particle systems settings points to its data item in  bpy.data.particles which is the ID object that the action (typically bpy.data.actions['ParticleSettingsAction']) will belong to.

thank you so much. I don't know why there is an additional setting I need to add to the end. It does not require it for modifiers.


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How to smooth a edge (rounding) it
I'm trying to learn how to smooth/round a edge of a model, currently I have a very simple case I can't achieve:
I created a sphere and cut it using the bisect tool, thats the result:

Now I'd like to round the top edge of this figure so it gets less shard, more rounded.
How can I achieve this? Tried selecting the top face and using the Bevel tool with no success =(.  (I'm a total beginner with blender) But it was near

You can't really get a large bevel there as it will overlap the preexisting geometry. Ideally you want very little geometry to begin with not just for performance, but because its much easier to work with.

So here I make a mcuh simpler globe, but add a subsurfce modifier to take adding all the extra geometry out of my hands. Now I can double tap g to slide down the second to top loop, giving me space to bevel the top one. Like so.

I then went ahead and removed that loop anyway as its pointless. This is the result.

Obviously this bevel is much too large, but it illustrates the principle I hope.

You can also use Proportional Editing.
Works well for dense geometry and doesn't require further subdivision.

Scale the top loop
Enable Proportional editing, set Falloff > Sharp
Adjust size as needed


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Creating a helix look for a marble track
Hi The following file shows how I created my loop. If is built from a base object that I will use to build the rest of the track. I am wanting to pull the ends of the loop apart in the direction of the arrows so that I can create a simple helix loop.
I tried dragging the end faces using proportional editing but it lands up pulling both ends in the same direction.
I tried using a curve modifier too but could not get it right.

Hello :). If you don't need the segments separated, you can achieve this easily using the Screw modifier

One possible way to go about accomplishing this would be to use an Array modifier on a single segment of your track. Make sure the origin of your track segment is at 0,0,0. Position the track segment in edit mode to the outside of your helix.

Create an array modifier on your track segment object using the Object Offset mode. Create an empty to use as the target object.

The basic deal is that every transform you apply to your empty gets applied between every iteration of the array. So, I rotate the empty 15° (360/24, the number of segments) about the Y axis. Then I moved the empty very slightly along the y-axis to create your helix effect.

The attached file contains the basic set-up. In my demo I used the merge options in the array to create a seamless loop. You can use the same principle if you want each segment to be disconnected. You will likely have to rotate your track segments very slightly about the z-axis in edit mode if you do in order for them to line up, or you will get this kind of stepping effect:

Thanks for this @Rekov. It is exactly what I was looking for but I can't seem to get it right: https://www.dropbox.com/s/gr5ze16bdj3h5t1/HelixObjectDemo-fail.blend?dl=0. Could you please take a look and let me know what I am missing

Ok so I am getting closer: https://www.dropbox.com/s/2mmjzo0axok9igg/Helix2.blend?dl=0

Hey @ABasel Your problem is that the origin of your cube channel object is not at the right place. You can fix this by selecting it in Object mode, then hit CTRL+A > Apply location. There are a lot of videos on youtube that show how to make a circle array in blender which might help more than  I can by text.


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How to combine multiple objects so adding material affects all objects?
I have 5 objects, one parent and 4 children. I used Cube Projection to unwrap and made sure to unwrap all objects at the same time. However when I apply a material from UV Map it only applies the material to one object at a time.
I cannot find a way to apply the UV Map material to all objects all at once.
What is the most effective way to combine objects to do this?
(Sorry if the answer is obvious, I am an absolute beginner to the software.)

Just to add -  the UV Map material only affects Parent object when applied even when all objects are selected

Please use the edit function to add information to your question, keeping the information of a question in one piece and formatted helps a lot in regards of understanding the situation and also helps keeping the forum focused and clean. Sharing a picture and/or a deducted version of your file(if possible) can also help others to understand and find a solution tailored to your problem.

Figured it out - needed to 'Join' all my objects rather than just have them in a family tree.


text:
Dragging Asset from Asset Browser Rotates It 90 Degrees depending on View Angle
Whenever I try to drag an asset from the browser, it will be rotated 90 degrees, instead of pointing upwards. It's pointed correctly if dragged onto a plane, but in the case I want to use it in, there'll rarely ever be a floor.
https://www.youtube.com/watch?v=aw3BYUSdDcU

I cannot replicate the issue. Maybe you can share the asset file? you can use https://blend-exchange.com/

Hello and welcome. While files, images, and external videos or links may be helpful additions they should not be the only way to obtain information about your issue. Don't make understanding your question rely on downloading a file, watching a video or visiting an external site. Use the builtin tools to upload images or gifs, along with thoroughly explaining the problem in written form so it can be indexed and searched for thus helping future visitors with similar issues.


text:
Knife tool problem
The knife tool creates overlapping vertex on a model, this didn't happen in the early of modelling.
Here is the line I created with knife tool

when you move the edge, you can see, there are new overlapping vertexs ( I moved the edges so you can see them )

is this a glitch?

The knife in 2.8 doesn't seem to be as convenient as in 2.7, it's hard to see and no way to see when it sticks to an existing vertex, I hope it will be improved, maybe it needs to be reported?

Judging by the inconsistent shading and after testing this, it is possible you already had double geometry before applying the kinfe. Could you try Merging (Right click > Merge by distance ) in edit mode and vertex select mode ?

I searched the other related posts, some said, it is because Blender doesn't support this kind of topology, however, it works most of the times if I use Snap vertex.


text:
In 2D animation, how to draw coloured shapes?
Absolute beginner here. I would like to make a very simple 2D animation using Blender, but am stuck at the very basic level, I don't even manage to draw any shapes. I have searched the internet a lot for guides and video introductions, and found quite a lot of them, but none seem to show what you need to do to draw basics shapes and/or the tools that they use are not visible in the Blender user interface that comes up when you select a new "2D Animation". After a lot of searching and trying out, I now managed to draw a filled grey rectangle, by selecting "Grey" from what I think is called the "Active materials menu", and then using the "Box" tool to draw the rectangle. I have not been able to draw in other colours.
As an example, I have found the following answer, which says that you need to "create a new (fill) material", but I have not been able to find out how to do that: Blender 2.8: Grease Pencil Fill Brush Not Working
So I am looking for a way to do the following:

draw basic shapes like a rectangle, circle, etc, each with a different colour.

I found the answer shortly after posting the question for the second time. For everybody who is puzzled about this as well, follow this description
By default, 4 materials are visible in the material box at the top of the screen (the one that drops down when you click on "Materials"): Black outline, red outline, grey filled, and black dotted outline. To make it possible to fill a shape with another color you need to add a new material.

To add a new material, open the "Material Properties" window at the right side, by clicking on the little red ball icon:

After that, press on the '+' sign in the corner, and a grey bar appears in the list. Then press the 'New' button:

In the properties that then appear, change the default 'Material' name to anything you like, and enable the 'Fill' property. Then click on the 'Color', which is black by default, and a color selection dialog appears, with a black color wheel. The easiest then is to use the color selection 'thermometer' to sample the color you want. Or sample any other color at all, except black, and then select from the color wheel:

I have not found an easy way to do this.


text:
Change the color (material) of the face depending on the distance
I need to set a particular material on the face of the mesh, depending on the distance between the center (or the nearest to "empty" vertex) of the face and the "Empty" so that the mesh gradually changes its color (material) as the "Empty" approaches.
I feel intuitive that I need to place the nodes "Position" and "Capture Attribute" somewhere, but I do not understand where to put them to work. The options I tried were unsuccessful.

Оfftopic:
I do not understand why geometry nodes being such a complex system, it has such a poor description. And all training is based on short, unrelated articles and video instructions from different parts of the Internet, which do not allow you to see the overall picture.

You can solve this task as follows:

Here I first convert the instance of the Empty into points, because only at this point I get a geometry with which the node Geometry Proximity can work.
If you would not do this, there would be no geometry to compare the positions with, because an Empty has no mesh.
After that you only need to compare the distance as usual and choose your material accordingly.

By the way, I don't think the Geometry Nodes documentation is too bad. I just think that there are way too many bloated video tutorials that you can't efficiently learn how to use.
Each node has its own tasks. It's like programming: Each command does something very specific. But with time you learn which things do what exactly, and above all you learn only by trying, in which combination which results can be achieved.
Don't get discouraged! Let the creativity run free and just keep going ... the rest comes by itself.

and my intuition has fully failed me :D


text:
Directing empties with geonodes
There is a cone and two empties. How to make, using geo nodes, so that the base of the cone is attached to one empty, and the top is always directed towards the second empty? Something like "Track to" constraint.

try this:

and you will get:

The subtract calculates the direction of the two empties as vector. The align euler to vector transforms that vector to a rotation value.


text:
Partial transparency of fabric in EEVEE
how to achieve the same effect of fabric translucency in EEVEE as in Cycles.

In case it is not clear: It is necessary that the light source partially shines through the material (fabric).
All the guides I found on the Internet referred exclusively to Cycles.

You can add a Diffuse or a Principled BSDF to a Translucent node with a (Shader) Add Shader node:

You'll need some optimization, but you'll achieve it.
Here is a way:
In the Eevee settings, you can change the Blend and Shadow mode to get good results:

Next, you have to enable Screen Space Reflections and Subsurface Translusency here:

Make sure the refraction depth is above 0m. Then, you also have to enable it here:

Try tweaking the settings to get your desired result.


text:
How to transfer information about original mesh
I have an icosphere.

I need to apply a "Subdivision Surface" modifier to it and then split the edges, but not all the edges, just the edges according to the original mesh.

it is not suitable for me to apply "split edges" before "subdivision surface", then blender also rounds the corners.

I need to transfer information about the "old" edges somehow, but I don't know how to do it.

To achieve the desired result, you would simply have to mark the edges before the subdivision with a boolean value using the Capture Attribute node.
You can then use this captured values after the node Subdivision Surface as a selection for the node Split Edges.

niiiiiiiiiiice ! ;) +1


text:
Procedural vine, direction of leaves, problem with detached branches
I create a procedural vine (or bean). But I have several problems with "leaves", "branches" and endpoints

Turn the leaves in the opposite direction from the branch (in the direction along the z-axis)
Is it possible to connect the branches to the stem or bring them closer?

The third problem is not critical, but if you have a solution, I will be grateful. All "branches" are removed in order to highlight the main stem, because of this the very top part of the vine is also removed, is it possible to fix it?

(Blender v 3.2.1)

If you really want to use a mesh as a base here, then I would solve the leaves with vertex groups, because that's the only way you can reliably separate the leaves from the rest of the geometry. Would that be an option for you?

@quellenform Yes, I need a procedural liana, with leaves and how exactly it will be implemented is not very important.

Although the question is actually three separate questions, here is the answer:
Use vertex groups to mark the leaves.

This way you can easily separate the geometry at the desired points and get your own curves for the stems.

This is practical because you can get a suitable rotation for the leaves directly from the curves with Curve to Points.

Also you can solve your second problem and get the next positions of the changed curve for your stems.

And the third problem is then self-explanatory, because you have clearly separated stem and stem from each other.

(Blender 3.2)


text:
Problems with the applying material using geometry nodes
I need to assign a specific material to the mesh using geometry nodes to make it look like a face.

And so that I can switch between different "faces" with a boolean (or other) switch.
The way I did it doesn't work.

Using vertex groups I was not able to create the correct eyes and other details.

(Blender v 3.3.0)

The node Set Material changes the material in the domain Faces.
Your vertex group, however, is, as the name suggests, in the domain Point.
Therefore, all faces that have any of their points in the vertex group will be selected.
For this reason you have to use the node Interpolate Domain (Blender 3.3), which explicitly selects only the faces whose points are all in the vertex group.
However, this alone is not sufficient in this concrete case, because there are at least four faces here, where all points are also in the vertex group, but which are not to be selected.
Therefore, you would have to subdivide the mesh further beforehand in order to make the selection more precise:

So i need to subdivide all the hexagons so that they have a vertex in the middle? Is there a way to do this quickly?

@arachnoden Yes, unfortunately, because otherwise this selection can not be achieved or processed as you want in Geometry Nodes. You can quickly achieve this with the modifier Subdivision.


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Incomplete cycle with "Cycles" modifier in graph editor
I perform the task on the walking man, I use the loop modifier to loop the animation in the graph editor. This is not in the task, but I am interested. Is there a way to make the modifier work not from the very beginning, but from a certain period of time? For example, if my character didn't start walking right away and did something before that. I tried to create actions in NLA, but there you can't cut the actions from the beginning and the end, only stretch them. How to do it correctly?

You can stop a clip in the NLA: Open the N panel > Strip > Action Clip > Frame End

You can stop a clip in the NLA: Open the N panel > Strip > Action Clip > Frame End:

You can also choose the start and end of the cycle in the N panel of the Graph Editor > Modifiers > Cycle > activate Restrict Frame Range:


text:
How to continue the same action in NLA
There are two actions. One of them is a simple movement along the axis, the other is a small rotation. If I copy the action, or set the number of repetitions to more than one - then they do not continue the movement, but start from the initial position, this applies to both movement and rotation. How to make the movement continue?

No matter how many tutorials I watch about blender, blender keeps reminding me that I don't know anything about blender.

I don't think that you can do that, but you can parent your object to an empty, then move and keyframe the empty where it is supposed to start the second action

@moonboots so NLA can work only with manually configured cycled loops? Actually, it is logical. A graph editor will cope better with this task.

This video is a pretty good introduction to the NLA and shows one way to break down an animation by imposing cycles onto free motion.

I don't think that you can do a Reapeat with Offset in the NLA. Parenting your object to an empty may help you in that type of situation, you can move it to the new location in order to create the offset.
But you can give a Cycles modifier to your action in the Graph Editor > N panel > Modifiers, and in the modifier you can choose After Mode > Repeat with Offset, which will repeat the action but will consider the last transform (location, rotation or scale) of your object.


text:
Change the color depending on the normal direction
I need to change the color of the cube surface depending on the normal direction.
For example, the surface of a cube should change color to red if its normal is directed upwards +/- 10 ° (on the Z axis).
Using shader editor of course.
Thank you.

This is a normal output of the texture coordinate:

X is red, Y - green, Z - blue
This is in the local space. If you have to get in world space, use vector transform node:

Then you can use Separate XYZ and Map Range to get some effects:

Just for the sake of completion, if it should be within the range of +/-10° the From Min value (and the From Max accordingly) has to be much higher, around 0.985 (surely there exists a formula somewhere to get it more accurate). And if you want a gradual increase in strength, why not set the From Max value to 1 to get the full range? If you just want to switch the strength between 0 and 1 I'd recommend adding a Greater Than > 0 node after the Map Range.

The Geometry > Normal output returns the shading-point normal in World Space.
The Math > Arccosine of the Dot-Product of that vector with (0,0,1) will give you the angle between the shaded normal and world 'up', in radians.

+1 Ah, that's the formula I meant in my comment above. And using the Geometry node instead of the Texture Coordinate node makes this setup work universal no matter if you rotate the mesh in Object Mode or Edit Mode without the need for the Vector Transform. @arachnoden I actually would choose this as the better answer because it gives you the more accurate result where you can easily specify the +/-10° or any other angle you like.

@GordonBrinkmann Cranitzs ' answer is just fine, IMO, and it was there first :).  I wouldn't want to tread on its toes at all. This answer is more to your comment, above,  I guess, than to arachnoden.

Crantisz' answer is fine for sure, and I think having a gradient can be very useful which is easily done with his setup. But for the sake of the question where it says "change to red" and where is asked for a certain angle range I still think your answer gives the more accurate result. However, I don't mind his answer being accepted, why should I?  It's just my personal opinion or preference.

This is exactly what I needed.


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Incorrect reflections (topology problems) in Cycles
Is it possible to fix these "cracks" that appear when rendering in "Cycles"?

Everything looks correct in EEVEE.

Maybe the problem is how I modified the "crystal".

(Blender v 3.6.1)

If you Apply geometry nodes, you can see hexagons are not flat. They are triangulated. Eevee seems to use different normal info (I'm not so techy, so I'm not sure it is calculated).
Hexagons are not flat because of your Transform Geometry node, that scales vertices on Y axis. This kind of math just can't result with real flat faces.
I wanted to move Dual Mesh after transformation nodes, but result was similar.

You can use just a Set Shade Smooth node and do selection for smoothing by Face is Planar node to specify co-planar faces, adjust Threshold value ...

... or you can limit Split Edges node to specify Edge Angle (I haven't used this node before so I can be wrong, but it solved the issue).

is it possible to specify each mesh face in the "selection" boolean input of the "shade smooth" node to prevent the "split edges" node from being used?

Yes it is ... edited.


text:
Having issue with mesh when in smooth mode
My issue is rather strange and not sure on a fix for it but when im in shade smooth mode the legs on my character are shaded a bit differently as i will show with an image if you guys have any ideas please let let me know if possible

is the edge a crease edge or sharp? In edit mode select the edge loop and try right click to clear sharp, and if that doesn't do anything hit n and in the item tab make sure the mean crease is set to 0

Flipped normals? Vertices not connected? You can always upload your file to blend-exchange, if you want to take us a look at it and place the link in your question. Please use the edit link below your question, if you want to add more info.

The shading is broken along an edge-loop, in those cases i would always check the normals first.
Solution:

Go in edit mode Tab
Select all with A
Follow up with Shift+N Recalculate Outside to correct the normals.

Explanation:
You can always check the normals with a "color indicating overlay" by switching on Face Orientation.

Example:

left looks similar to your shading, right shows the overlay activated

The Entire model should be blue if all normals are ok, if red is visible outside then those areas have bad (facing inwards) normals and you can either manually select the red faces and press Alt+N to open the Normals menu

and Flip the normals of the selected faces, or use the in most cases easier, "select all and recalculate outside" method explained at the beginning. There are cases where the Recalculate Outside function does not manage to fix all, just mentioning. In those cases manual flipping would be needed.
Happy Blending.

Thank you soo much for your quick response and i think i fixed it thanks to your help


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How to move a dense mesh irregular object above other object surface in a especific direction?
Hello I m new in Blender and I ve trying to solve the next problem for a long time but I couldn t find an appropite solution. So I m writing to you and maybe you can help me. My problem is the following' I animate one object (A) with some partticular movement then with (control L-- animation data) linked this movement settings to other object (B) so all the group have the same behaviour. Now put on the pathway of the object B linked, another object (C) and now I want the object B  when contact with object C slide obove object C surface contacting with it with out overlaping meshes and then, when contact finish,]object B follow come back its original pathway...I try setting rigid body and collision in physical properties but meshes of object B and C continues overlapping.

Overcomplicated. What is object A for then?

Object A is a uv sphere where I set a movenmet...then object C is a superior part of a Suzane head and  B inferior part of Suzane head...I want when  play animaction inferior part of Susane head B move contacting according C surface superior part of Suzane head follow the movement dirección setting in A and Linked in B


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camera view as a texture?
Is there any way i can use the camera view as a texture in realtime? i know you could do this in the blender game editor before using python, but now i don't know if there is a way i can use the camera view as a texture (or colour output, basically) without rendering or baking it
kind of like a security guard monititor or a portal effect, i think you could do this kind of effect in the compositor using masks but that wouldn't really help

I Lately thought a lot about this. I think the easiest way is to write an osl shader, which translates secondary rays by a vector. Don't know how to do this tho.

I'm looking for this too; to make something like this : https://www.youtube.com/watch?v=OWnC9tSA3iA.  Did you find out ?

You can still use python for Scripting. I have not tried it yet but from searching web there are commands to put in script to render the camera's view, save that to file, then set object texture to file, write another script to constantly update the objects texture.
Render camera view to file.
Set texture to file.
Keep rendering and updating texture in background script.

ah cool thanks! i don't know much python but if you get any updates on that please let me know


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Selective cell fracture
Hi i'm trying to make a scene where a bullet shoots itself to the corner of a concrete wall, making the corner pieces fall off. But i'm not sure how to do that without the whole wall breaking.
also should i just use a smoke simulation for the dust that happens when a piece brakes? or is there a much more efficient way with particle systems

You could always keep some of the bits of the wall a passive rigid body instead of an active so broken pieces still collide with it. Also a mix of low-density smoke sim with some small rubble particles would probably be best.

i've never played with smoke sims or particle systems, is there a tutorial that you can direct me to so i can learn this?

https://www.youtube.com/watch?v=_IDBfQnttiE

thanks, but do you have any ideas on how to make it so that it activates when the debris is hit or something?

Just set the keyframes of the particles or smoke to be when the bullet hits


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Anyone know how to make time remapping animated
I want to make a scene which goes from normal speed to slow motion then normal again
this question was asked a while ago but on a previous build
I'm not sure how to do this and it's not just particle effects and simulations, i want animated objects to be manipulated too without having to go through the process of changing the frames of every object


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Random displacement of the vertices of the sphere from the center outwards
I have a flattened low-poly sphere.

I need the vertices to be offset by a random amount along the Z-axis using the geometry nodes, but relative to their normal, ie not the global Z-axis, so that the shape looks like an asymmetric star. In other words, the displacement should go from the center in all directions to the outside, so that something like this comes out:

Unfortunately, I can only move it along the global Z axis..

 (Blender version: 3.6.0)

Offset Vertices from normal:

Result:

Great. But what exactly does "Power" node do?

Values closer to 1.0 become much rarer. Change the exponent to control the density of the needles.

The only adjustment you need is to use some scale of the Normal to offset vertices, instead of Object-Z:

This version selects points around an icosphere to offset outwards:


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Random rotation with geometry nodes
It is necessary to make the object constantly rotate randomly when the animation starts using "frame" python keyword (nothing bad if they are sharp jumps from one angle to another).
In this regard, 2 questions:

Why doesn't my scheme work (what does the red line mean?)

How to do random rotation correctly?

You can solve this relatively easily with the help of the node Noise Texture:

Here I use Scene Time as base value and a very low value for Noise Scale.
The node Noise Texture produces values somewhere between $(0,0,0)$ and $(1,1,1)$, which I map with Map Range to a rotation range from $-2\pi$ to $2\pi$.
With this solution you get different rotations over your whole timeline without (visible) repetition.

you could e.g. use this node setup:

result:

The red line means: this connection is forbidden and won't do anything.
You connected a circle (one value) with diamond (means field value = multiple values). That's not allowed.
Note: GN as well as Blender inside always works with radians, not with degrees. So you won't be happy with random values from 0 to 360. Better take 0 to 2*pi.
if you want to transform just one object, use this:

The ID will be filled with a constant integer with transforms the field value of the random value node to a single value node.
UPDATE:
ok, here you are:

This is closer to what I'm aiming for, but if you turn on the animation for a long distance, you can see a cyclic algorithm by which the object rotates, that is, it's not completely random rotation.

i updated my answer - now with sharp jumps


text:
Analogue of "Solidify" modifier using geometry nodes
I am trying to create a conical pipe of a certain thickness.

But the combination I use leaves the inner walls of the pipe unfilled.

I need an analogue of the "Solidify" modifiers using geometry nodes to solve this problem and, for example, create a cavity in a regular cube or sphere. Example:

Your setup is good so far. What you need for the inner face is simply to join the original mesh before extrusion to the extruded one. Since the normals on the inside are facing in the wrong direction now, you need to also place a Flip Faces node after the Curve to Mesh before the Join Geometry node.
The problem with the Extrude Mesh node in GN is that there is no "Even Thickness" setting like in the Solidify modifier. So in some or more likely a lot of cases you will not get a similar result.

Too bad that various modifiers have not yet been translated into Geometry Nodes. However, there are positive developments in this direction (example: "Bevel Modifier").

You mean... Bevel is in the latest version?

@RobinBetts I was wondering the same... I got 3.3.0 Beta and 3.4.0 Alpha but I didn't find it.

@quellenform Where can we find the Bevel Modifier in GN? I'm really looking forward to that...

@RobinBetts ...I think it will take a few more versions, because there is still a lot to do here.

@GordonBrinkmann Hans Goudey wrote in a post dated Thu, Jul 28, 18:42: "There is already work underway for a new bevel implementation as a node." Link

@quellenform Ah okay, that's nice to know.

This is a strange scenario, but for a plane this worked.  It's two extrude meshes, one set to zero and the other to the "solidify" size.


text:
How to use "Merge by Distance" node?
There is a certain model duplicated by the "Instance on Points" node. They overlap perfectly, but for some reason the node "merge by distance" refuses to connect them. Am I doing something wrong?

Your geometry is composed of duplicated instances.
Separate instances can't be merged together as they are equivalent to different objects.
To merge the ends together you must realize instances first with a Instances > Realize Instances node.

Thanks. Isn't it weird that "Join Geometry" joins instances and geometry without warning?

No, join geometry does just that, joins it. It doesn't merge it nor fuse vertex together.

@arachnoden "Join Geometry" does the same thing as pressing Ctrl+J in the 3D view. It puts all the geometry from one object into the other, but doesn't do anything further with it, overlapping or not.


text:
Making a barrel with geometry nodes. Problems with rotation
Trying to make a barrel with geometry nodes. I'm using the Mesh Circle node as the origin of the points and the cube as the board. But something is wrong with the angle of inclination at the beginning. How to align the boards vertically so that they look like a barrel?

You made it nearly right. You just forgot the align euler to vector node ;)


text:
Problems with transparency in EEVEE
Help me please with EEVEE.
Blend-file:
https://mega.nz/file/eH5yRahY#4v3JtwS1N7OY_hAKdnPP6oDQZQVWk7F36D7fuzkCvqo
There is an empty capsule inside, the door of which is transparent. There are two problems with them:

The wall behind Susanna becomes transparent along the contours of Susanna herself (If the suzanne is removed, the walls cease to be transparent).

Suzanne's image stretches as if the capsule was flooded with water. It should not stretch (This can be checked by switching to Cycles)

Сhanges that I made in the program:

Since Eevee is no Raytracing Engine like Cycles, it doesn't really take the glass thickness into account for the refractions. So in order to make it work as if the glass had some thickness to it and is not just a giant block of glass enclosing Suzanne, in the Material Properties you have to set the Refraction Depth to some reasonable value above 0. In my example I've set it to 0.1 m (still very thick for a glass plane) and it already looks a lot better... and I guess this helps with other issues as well.


text:
How to make furrows darker?
Another day of the 3D artist. How to make furrows darker?
is it possible to make an analogue of "ambient occlusion" using only the Shader Editor? The gradient texture doesn't work as I expect.

(Blender 3.2.1)

You are in Eevee, in Eevee there are at least 2 solutions: the AO node and the Dirty Vertex Colors.
Use an Input > AO node as factor in your Shader Editor, you just need to activate the option in the Render panel:

For the Dirty Vertex Colors solution: Switch to Solid viewport shading mode and switch to Vertex Paint mode, then go into the header menu > Paint > Dirty Vertex Colors:

Tweak the factors in the Operator box until you get what you want:

The operation has created a Vertex Colors in the Object Data panel. Switch to Rendered preview or Material preview, in your Shader Editor create an Input > Vertex Colors node, use it as factor:

In Cycles there's also the Geometry node and its Pointiness output, you could bake the result if you want to use it in Eevee.

is there a way to achieve this result without using the "Ambient Occlusion" option? Using only the Shader Editor.

You could bake a AO map or a Pointiness map in Cycles and use it in Eevee

In Eevee itself you could use the Dirty Vertex Colors in Vertex Paint but it needs more geometry that what you have currently, so you'll need to subdivide, but here again you could bake a map to come back to a low-poly version

Sorry, I didn't look carefully at the image, that's exactly what I was asking. Thank you.

Oh actually it could work fine with Dirty Vertex Colors too, I'll edit my answer

This is also a great option, special thanks for it.


text:
Creating "Text Cloud" like in comics
I need to create the "Text Cloud" like in comics. There should be "layers". The top layer is "Text" - the object inside the "Text Cloud". It should be higher than the cloud, i.e. at the highest level and be visible all the time. The second layer is the "Text Cloud" itself. It should be higher than the other objects in the scene, but lower than the "Text". Other objects in the scene are the third layer, they should be below the "Text Cloud" and the "Text" itself. I suspect that a composition needs to be applied here.

 (Blender v 3.3.0)

Are you sure you want the speech bubbles to be 3D? Always-on-top visibility combined with shading can look weird.

@MarkusvonBroady How do you achieve always-on-top visibility? -- With an emission shader you can get rid of the shading if you don't like it. This speech bubble has flipped faces, backface culling + emission. But it gets hidden other objects in the front.

@MarkusvonBroady If this is not possible in the 3D version, then let it be 2D, if the condition of three layers is observed. But I will be surprised the 3D option is not possible in Blender

@Blunder one idea is to take advantage of Alpha Blend problem: https://i.imgur.com/LQzSi87.gif - you could do this dynamically by moving an object towards the camera with a driver or a constraint, and then moving the geometry within the same amount using geonodes. Or as OP says, just separate renders, composited in the order you wish. Or, what I'd go for, animating the speech bubbles to rotate as camera rotates, to simply stay closer to the camera. You probably want to align the text and camera orientation anyway for good readability (or maybe not, or maybe partially...)

@MarkusvonBroady Yes, I saw how a similar problem was solved with the help of a composition. But in the example there were two layers, and I have three layers, and I don't know how to do it correctly.

This version does the work in-scene, in front of the camera. The speech bubble is constructed in the XY plane, origin at its point, its components gathered into a collection.
Here, the bubble is set up as a GN modification of the speaking object. Just 3 simple clusters:

.. which adjusts the location of the bubble in the speaker's space, and lets you change its apparent size...

... which rotates the bubble to face the camera, (construction Y up speaker Z)

... which scales the bubble towards and away from the camera, allowing you to bring it in front of other scene objects, without changing its apparent size.
so.....

It works fine with a 3D bubble, too, (included in .blend) but there are less obvious decisions to be made about outlining, lighting, etc. Maybe come back with complaints, on that one.

.

Not what i expected, but works even better. Thank you. I suspect you are from the Blender development team.

This is exactly what I had in mind when I wrote "or maybe partially" - very nice effect where the bubble is not static, but is readable at all times!

@MarkusvonBroady + arachnoden I'm glad it met the specs :)  Did something like this a while back for captioning a map, with constraints and drivers, as suggested. But it's _so_much easier to construct and use, in GN.  :D


text:
Control of instance parameters through sockets (geometry nodes)
I created a primitive torus using geometry nodes.

Then i created an array of such rings using a line (Instances On Points).

I need the diameter (socket "Main Diameter")

of these rings to be adjustable depending on the height (the higher the vertex/ring on the line, the larger the diameter). How is this possible to do?
In the end I expect to get something like this:

 (Blender v 4.0.2)

May I suggest to read these two posts: https://blender.stackexchange.com/questions/280188/why-cant-the-radius-of-an-icosphere-be-set-depending-on-position-with-geometry and https://blender.stackexchange.com/questions/274485/how-can-i-instantiate-a-procedural-node-group-with-different-parameters ?

You cannot set multiple radii for the object to be instanced, because this is a single object which just gets duplicated by the Instance on Points node. So you would have to manipulate the resulting instances, for example by ID with the Scale input of the node. However, this would change the overall thickness of the torus as well.
So what I would do is instance curve circles instead, scale them by ID (or maybe Z position, whatever you want) and after instancing convert them using a Curve to Mesh where you use another curve circle as profile. But you have to use a Realize Instances node, otherwise the profile will be scaled according to the scale of the instances as well.
For scaling I used the ID in this example, you have to add something to not have the first scale at 0, but the order of adding and multiplying can be swapped, it depends on how you want to set the base diameter and how much it should increase per step etc.

Here basically the same setup, but using the Z position for scaling. In this case I multiplied the Z value with 0.3 instead of 0.1 like I did with the ID and the result is the same as before:

One of the major differences between these two setups: As long as the line keeps its height, with Z position the maximum diameter stays the same no matter how many rings you have. With ID the maximum diameter increases.

Thank you. It turned out that I overcomplicated the scheme


text:
Create map from image
I have a simple color image. I need to convert yellow to black and green to white so I can use the image as a map. (for example as roughness map)

You could simply put a ColorRamp after the Image Texture of your arrow

You could discriminate along any of the dimensions of any of the color-spaces, but maybe the most general way is to measure Distance along all 3:

This is cunning.

As @moonboots said, you can just remove the Separate RGB from your setup and you will have a grayscale version of your texture :

If you want the yellow part to be black, you can just flip the color ramp :

Then you can just add a RGB Curve node to tweak the colors to your liking :


text:
How to add object coordinates to instance coordinates?
I'm trying to create infinite "Teleport Waves"

and everything is going well until I try to move the teleport itself. Then the waves stay in place.

My attempts to intercept the coordinates of the object itself and add them to the coordinates of the instances were unsuccessful. What am I doing wrong?

 (Blender v 4.0.1)

Just set coordinates to original:

Relative means torus will change position than you move object because coordinates are relative to current object, not to world center.


text:
Extrude only one face using geometry nodes
There is a subdivided cube (4x4x4 vertices).

I only need to extrude one of his faces, such as the middle one on either side using geometry nodes.
But when I try to specify a vertex group, all planes touching these vertices are extruded.

The result should be as follows(Using geometry nodes):

I need to be able to extrude not only middle face, but any I want.

You can extrude a specific face in Geometry Nodes by selecting it.
The selection can be achieved by comparing the current index with a value of your choice. Of course you have to know this index or find it out by trial and error.
There are several index viewers that allow you to view the index of the faces.

This question has also been asked here before: How to show index of faces, lines, points?

An alternative would also be the selection via a vertex group (Blender 3.2+):

Utilities > Compare node (Integer, Equal) ... or Utilities > Math node (Compare, Epsilon 0)

@vklidu Thanks for the complementary information!

but how does one know what index is needed for the desired face?

@rothloup I have updated the question accordingly, and hope this helps you.

It helps me understand, but doesn't help me solve the issue - there is no way to know what index the relevant face unless it's for a specific case.  Thank you.

@rothloup After all, the question here is "How can I extrude only one face using geometry nodes?", and this answer here is the solution. If this one doesn't help you, please create a new question so we can think about your specific task.

of course.  not criticizing.

In case you want to extrude using a Weight map:

Geometry Nodes:

You can use the Capture Attribute node to transfer the vertex group information to the face corners:


text:
How to control the scaling with the Color Ramp node so that the scaling is smooth?
I need to control the scaling of the mesh with a color ramp so that the effect is smooth like the mesh on the right. I tried different combinations of the nodes in the picture, but nothing worked for me.

The mesh on the right is smooth only in middle, not on the start and end of the gradient. Have you tried switching "Linear" mode to other options?

@MarkusvonBroady It does not have to be exactly the same as on the gradient. The main requirement is that it should be guided by a gradient.

Scale Elements will separate the Selection, and then separate that by mesh islands, and then scale the islands. So if you don't want the cuboid to be simply scaled as a single object, you need to separate the horizontal edges. Then you need to simply pass the $z$ coordinate to the Color Ramp, but since the ramp expects inputs in range $[0,1]$, all $z$ coordinates below $0$ will read as $0$, and all $z$ coordinates above $1$ will read as $1$ (they will be clamped to the expected range). To combat this I use an Attribute Statistic node, but you could as well e.g. just divide the coordinate by the height of the mesh if it started at zero as in your case… Notice the "Ease" mode…

Thank you. But explain to me please, what does node "Not Equal" do?

@arachnoden vertical edges are at an angle of $90°$ to a horizontal vector, so I select edges that aren't at that angle. The Vector $<1, 1, 0>$ was picked, but any vector with $z = 0$ would do as long as both $x$ and $y$ weren't equal (or very close to, due to εpsilon allowing some fuzziness) to $0$ (because an edge parallel to $y$ axis is at $90°$ to $<1, 0, 0>$ and an edge parallel to $x$ axis is at $90°$ to $<0, 1, 0>$, and we want to select those horizontal edges).


text:
Text along curve or circle with Geometry Nodes
I'm trying to align text along a circle or curve using Geometry Nodes,

but it's very messy.

Where did I go wrong?
 (Blender v 4.1.0)

You can try this node setup:

But be aware that this does not take the right distance between the letters into account. But the rotation works.

Note: one thing is, the letters are not at position $(0,0,0)$, so if you translate them (which means: offsetting) the letters won't be on the points of the circle - as you have expected it. That's why I first do a set position to $(0,0,0)$ so that the instance on points does, what we expect it to do. The Align Euler to Vector node gives the instance the right rotation by using the curve tangent node.
You don't need a Sample Index node, because we plugin the rotation into the Instance on Points node, which "main" node tree is already the curve.

+1 ! it will look nice if you add a space after the last word in the String node! :D

@HarryMcKenzie: that's only a thing for a Pro like you are! ;)

i wish! haha XD


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Size of the instances depends on their position
I need to make some changes to this leaf generator. The size of the leaves should vary depending on the height. This means that the upper leafs should be smaller than the lower ones.

(Blender v 3.2.1)

You can add a Position node and get the Z value with a Separate XYZ node, then use a Map Range to fit the output values to input range and plug it into Scale on the Instance on Points node.
By the way, it took me a while to figure out some values on the Map Range node. Your "Cube" object has a scale of 0.037, it's always better to apply the scale with Ctrl+A before creating the Geometry Nodes. If for any reason you cannot work on without applying the scale, then your plant will "explode" into a gigantic mess once you do that.


text:
Is it possible to make a sphere that made of equilateral squares?
It is possible to make a sphere out of equilateral triangles, but can you make a sphere out of squares of equal size?

Short answer is no - this is the reason there are so many different "projections" of the map of the earth - you cannot map a spherical area to a rectangular (or square) area without distortion of some sort.

Thanks, i am sure the link will help

https://blender.stackexchange.com/questions/227269/how-to-shrinkwrap-bunch-of-planes-to-a-sphere-while-maintaining-the-planes-dime


text:
How can I make the robe act like a robe?
So I'm Making a robe for a character pose that involves a robe. From the angle in the image, the robe somewhat looks okay.
But when you look at it from the other side, it tells a different story.

I've tried weight painting the robe to the specified legs, but every time I try, It just drags more than I wanted.
Here's the file to the model.

It depends on how close to reality you want the robe to behave.  If you want a reasonable approximation, you're going to have to give the robe is own bones and animate them because robes flow according to both your movement and cloth physics.

as Marty says you can give it bones, or you can give it cloth physics but it will be a bit more complicated to set

Thank you. I think I got the robe to work


text:
How to array a simple model vertically and be able to use nodes and edges?
I am trying to use Blender to model a building that repeats over 30 stories. I want to use this repetition to my advantage and use maybe a tool such as Array (My AutoCAD terms into Blender) to only adjust the first floor and have the rest of the 29 arrayed stories adjusted accordingly. Is this something that can be done? Also, by arraying the floor vertically (Z-Axis), how can I access the edges and nodes individually to export coordinates and connections?
The image below shows the current state of the file.
I need to export a lot of data from Blender with scripting, so access to all nodes is important. I would like to think that it is possible to somehow repeat one storey over multiple times.
Thank you.

You can use Array modifier.

In order to get all data, you can copy object in python and apply modifier on copy.


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Geometry Nodes - Instances - Having problem with directions of instances
I would like the instances to follow the Y axis of the mesh vertices and flow along/follow the surface. The "Align Euler to Vector" node enables alignment along the Z axis, but I cannot get the alignment on another axis.

You need a vector, that points into the direction of what you call the Y axis of the mesh vertices instead of using the Normal as the Vector input. And you probably need to align the Y instead of the Z axis in this case.

If you want to work with an existing grid where the directions of the edges along the X-axis and Y-axis are easily separable, you can proceed as follows:

Use the node Edge Vertices and get the direction vector of each edge with the math node Substract.

Then convert these vectors to positive values so that you can compare them with the node Compare (Equal Direction Vector) and a certain other direction (In this example I compare it with the X-axis and an angle of $45°$, which is $\frac{\pi}{4} = 0.785$ because here it requires radians).

This will give you a selection, which you can additionally make switchable with the node Switch, as I show in this example (You don't really need this, but it's helpful for testing).

If you now convert the mesh into curves using the node Mesh to Curve and your selection, you will now get curves on a specific axis where the tangents have been recalculated.

The node Curve to Points will finally give you the respective rotation of each point and now you can instantiate your cubes directly at these points and use the obtained rotation.


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Duplicate parent and children by python,but children are in the wrong place
I use scripts below to duplicate and move one parent and its children. When i move parent to another location and run the scripts, parent.copy() moves from the new original location, but children.copy() move from original location. If I apply rotation & scale in parent, children move correctly.What's wrong with it? offset is a Vector(()). Thanks!
def duplicate(offset):
    children = []
    parent = bpy.context.object
    p = parent.copy()
    for ob in parent.children_recursive:
        a = ob.copy()
        a.matrix_world.translation = ob.matrix_world.translation + offset
        print(a.matrix_world.translation)
        children.append(a)
    p.matrix_world = Matrix.Translation(offset) @ parent.matrix_world
    print('___')
    for child in children:
        child.parent = p
        child.matrix_parent_inverse = p.matrix_world.inverted()
        print(child.matrix_world.translation)
    print('step3')
    for ob in children:
        bpy.context.collection.objects.link(ob)
        print(ob.matrix_world.translation)
    bpy.context.collection.objects.link(p)


text:
What can cause a UV to not copy properly?
I'm trying to copy a UV map from 1 object to another identical object but the UV coordinates don't match up.  Can anyone tell me what could be wrong?

First Image is the Good UV map I'm trying to copy from.  Second image is of course the result of copying the UVs from the first image.  The third image is the UV map from BOTH objects, they are identical which is why I'm confused.  When I select a section of vertices, say the leg for instance, the vertices on the UV are mostly hair UV instead of the leg UVs (Fourth Image).

The problem is that your two objects are not identical.
When you copy UV, it's copying via topology.  Basically what that means, in this case, is that it copies the data in the order that the face-corners are stored.  If one model has its face-corners stored in a different order than the other, different face-corners will get the UV than expected, and the UV map will look the same, but the textures will be in completely different spots.
Somewhere, some process made it so that these seemingly identical models are not identical, not under the hood.  Many import and export algorithms don't pay much attention to index order, and can leave you with models that are subtly different like this.
If you need to restore index order for something, you can look into a "mesh sort" operation to try to get their mesh data sorted identically, but it's probably not worth it-- instead, these are otherwise identical models, so just use the one with the UV you want.

I see, was gonna rig the second model since it's positioning is easier, but of course I set up the UVs on the first model lol.  Oh well, thanks for the help.


text:
Why are my circular UVs turning oval?
I'm trying to unwrap my first model and there's some problems I can't get around. First, my circular faces are getting an oval shape in the map (image below), second, sometimes a mesh will get much bigger in the map than it is in the model and I don't know how to make the canvas map larger for it to fit in. Thirs, some of my faces are turned into edges in the uv map. Can anyone shed some light in what I could do to solve this? Thanks in advance.

Most of these are just from the fact that UVs do not necessarily correspond with the shape of the faces they came from, just how they connect with each other. However, faces really shouldn’t be squashed so thin that they look like edges. Are you sure those faces are selected when you’re unwrapping? Did you set up seams correctly, or is there something that’s causing the faces to have to be squashed in the unwrap?

What is the object scale in N-panel? Can you try applying scale (ctrl + A) if the scale value is not 1 on all axes?

What command did you use to unwarp, IE, what entry in the unwrap menu?

Your object might have non uniform scale
Unwrapping unmodified circle works as expected

However, if we scale it by 2 on x-axis, and then reverse the scale in edit mode, the unwrap is squished even though the object looks identical to the first one.

The previous action sets the object scale to 2,1,1. While calculating the UVs, Blender sees that the object was scaled by 2 in X direction, so it must account for that and not give extra texture space in X direction. Hence the UVs get squished.

[blender: The object looks like a circle but it is scaled by 2 on X. So originally it must look like in ellipse. I'll perform the operations on ellipse,since that's the original geometry]
You also get a reminder in the status bar.

You can fix this by applying the scale. press Ctrl A and choose scale. Goto edit mode and unwrap. This will set the scale to 1,1,1 => tell blender to set the original geometry to what it looks like right now


text:
How to make different object's UVs proportional between each other?
I'm making some uv maps from several objects that share the same height.
But when I do unwrap, the map scales towards the bounds of the "editing canvas".
How can I unwrap this objects in a way that the maps end up proportional between each other?

You could join them, unwrap, then separate? Then you'll scale up the UVs keeping the same factor every time?

I could, but the easiest way to do it would be to create faces linking them, unwrap and then figure all the mess in the uv editor, I was hoping for a faster method.


text:
What is the best method to "glue" a mesh on top of a face?
I'm making a super simple club as a study and I've modeled a stud that I'd like to add to the model. I'd like to know how can I "glue" this stud in the faces of the club in a way that it follows the z axis angle where the face is. Thanks in advance!

did u try parent?

Could you please elaborate on that?

If the 2 objects are separated, join them with Ctrl J, or parent the small piece to the big one with Ctrl P. If they are part of the same object but you want the 2 meshes to be merged you need to do a bit of modeling. Please give more details on what you want to do

Try this https://blender.stackexchange.com/a/282835/142292

To get them to line up, investigate Snapping set to Face. When the 'stud' is where you want it use Ctrl P > Object (Keep Transform).


text:
Blender rendered image is blocky
The viewport shading looks different compared to the actual render.

What could cause this?
If anyone wants to check out the file it can be downloaded here: https://mega.nz/file/gs0SmThD#2lBTSQsVocjnbZ2IN7_1Ih8HDpWeeNSw2j8LhY0z05E

Please don't use an external site for uploads and upload any file in native .blend format rather than compressed. https://blend-exchange.com/help

I think everything got duplicated by accident. There are 4 lamps, 2 floors, 8 fence posts, 10 window frames, etc. I highly recommend giving the objects proper names then you see easily in the outliner that there are 4 lamps & not only 2 ;-) If you want to add lights I recommend scaling down the scene to real-world size. At the moment the lamps are 16m tall and require a 20000W light to shed some light. Also, 16000(!) samples + no threshold is crazy. This takes hours to render. Such a low-poly scene will already look nice with only 20(!) samples+denoiser =>  https://i.sstatic.net/5Jjc5.jpg.

your problem is called z-fighting (you can search here for that) and it happens, if you have two objects on the same place with the same form and size, Blender does not "know" which is in front. So you should delete your double objects. You can "check" for double objects by just selecting them and move them to see whether there is still another.
Watch here:

if i render after moving away the double object, it looks fine:

but still the lower object is double too...


text:
If there is any way in Blender I can use a mathematical formula to control particle density?
I'm trying to visualize something in physics. I have a formula that determines the density of particles at each point in 3D space. How can I visualize this?
For example: density=1/r^2

If you are referring to particle emitter you can get a close approximation directly or run a script for greater accuracy by utilizing the curve guide force.
Create a sphere object and add an emmision particle system to it.

Emmission settings:

Set the frame start and end to 1 to have all particles instantly generated.
Set emmision source to Emit from Volume.

Viewport Display settings:

In the viewport display options disable show emmiter.

Field weight settings:

Ensure Curve guide is enabled as full field weight. (disable all others as desired for animation)*
Add Forcefield Curve Guide:

The curve guide object initially starts with 5 points but can be subdivided and points placed to approximate your function quickly along the x & y axis. (though infinite at 1/r^2 where r=0 isn't going to occur)
If you require high degree of resolution & accuracy you may wish to modify the curve through a script, but it will still simply be placing sample points along the curve.

import bpy
from mathutils import Vector

obj = bpy.data.objects['CurveGuide']

spline = obj.data.splines[0]

desired_pts = 21

if len(spline.points) < desired_pts:
    spline.points.add(desired_pts - len(spline.points))

pt_start = -10
pt_end = 10
step = (pt_end - pt_start +1)/len(spline.points)

position = pt_start
for pt in spline.points:
    if position == 0:
        pt.co = Vector((position, 1/(0.001*0.001), 0.0, 1.0))
    else:
        pt.co = Vector((position, 1/(position*position), 0.0, 1.0))
    position += step

Reulting particle distribution:

1) Enable Extra Objects Addon

2) Add Mesh > Math Function

Use Geometry Nodes to display points