text:
How to convert LinearRing/mesh to face
I have many lines, they should be surfaces.

How can I convert all of them to surfaces?
The result should be like this.But there are two 2D polygons.I want two 3D polygons.

Do you mean your 2 sets of lines should be connected together, or that each individual set of lines should be a polygon ?

each individual set of lines should be a polygon

If you just want 1 polygon each, simply select all vertices of a line in edit mode and hit F, but I don't think that's what you're going for.

I want 1 polygon each,because it's a LinearRing.  The opration 'select all vertices of a line in edit mode and hit F' will create more polygon


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can not export gltf with build modifier
I have an animation with build modifier and position changing.
I drag the gltf file to the glTF Viewer.
But the animation not contains the build modifier animation.

There is only position changing.
How to export the build modifier animation.
glTF exports in this parameter

I'm not experienced ...but when I don't know how to get out anim I use alembic format ...

I need to show the animation in web.I don't know whether the alembic format can be showed in web

No, it was meant to use alembic as intermediate format to translate modifiers anim to something readable to other formats. But what I tried now - export to abc, import abc, export as gltf, import gltf ... didnt work either. Sorry my inputs :)

The easiest way is probably this.

@scurest It works. But when the big data loaded,it will get stuck.

It ignores the build modifier probably because it is Blender specific and gltf format doesn't recognize it.

source: Stack Exchange

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

sort: votes


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Can I use still use blender 2.79?
Currently I am still using the blender 2.79 version. Can use the game engine of blender 2.79 to make and publish games?

No it’s is not duplicated. It’s is not at all same with that question.

Sure you can. Just keep in mind that no updates and fixes will be released anymore, so use at your own risk. I actually use it with no complaints (along with UPBGE 0.2.5b).

Means can I use the games made in it for commercial purpose? I mean can I publish the games without any cost?

You always could, there's just some caveats. See some details about licensing here:
https://docs.blender.org/manual/en/2.79/game_engine/licensing.html

Of course you can still use Blender 2.79 & its game-engine. No one can stop you from downloading it. But you could also use a UPBGE 0.3x or 0.2x release for more optimal and bug free software.

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


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How to do a looped animation with correct rotation using Geometry Nodes?
Recently I am learning Geometry Nodes. I follow a tutorial and create a swimming fish but I want to loop it.
Currently the fish loops correctly in position but once I add rotation node, the head doesn't rotate as expected and whole fish is smashed in frame 125. Using curve can also solve the problem  but I want to figure it out with procedural calculation. Is there any method to solve this?
Thank you so much!:D

Node tree:
File: https://www.dropbox.com/s/g800uv1j1mmq71a/fish_NC.blend?dl=0
Tutorial I followed: https://www.youtube.com/watch?v=lvHLQGUo-y4&t=263s&ab_channel=Bbbn19

I see you are new here. Welcome! There is a feature built in to Stack Exchange for uploading and adding images to your post. Please use it. Otherwise, if your Dropbox file ever gets removed, how will anyone be able to see your reference image? I tried to fix that for you, but your animated GIF is 13.6MB (well over the 2MB upload limit). You are not making an HD film here, so re-export your animation at a lower resolution and maybe skip every other frame as well (Output Properties > Frame Range > Step). If the image is displayed too large, use the HTML syntax: <img src="path" width="420"/>

Similarly, there is a way to host your .blend files that  are part of Blender Stack Exchange posts. It is blend-exchange.com But if you are going to use it, be mindful of the size of your .blend files, so as not to waste the hosting space that is generously provided by the site owner to the BSE community for free. Aim for 1 to 2 MB. If you are not sure how to keep your file sizes small, using Dropbox (as you are doing now) is also okay.

Thank you for reminding. A new gif is added. Unfortunately, I got an error when the file (1.8M) was uploaded on blender exchange. So I will leave it as it is.


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Making a shaking leaf ball character
Currently I am making a character which is a leaf ball. Everything looks great until I try to rotate it with armature.
I use hair particles to create leaves and cover it on a sphere. When the sphere rotates, leaves will shake a bit, or I can use force field to make it wiggle.

But the fact is when the sphere rotates, leaves rotate strangely. I do some researches and discover that when particles' rotation orientation axis is set to normal, particles will be rotated while the mesh rotate.

I try to use emitter as well but particles can't stick well on surface and thus it fails.
A leaf ball that can perfectly follow sphere movement and at the same time leaves itself can be shook is what I want. Is there any other ways to create similar effect?
File:


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Render completely messed up?
I have a problem when rendering my scene. It looks like after a certain distance everything is blurred out completely, some objects are missing and some other weird things are going on. However in the viewport the rendered view is fine. Camera clipping is set to 0.1-100 m so it shouldn't be a problem. Do you have any idea what is going on?

Edit: Here's the link to the .blend file: https://drive.google.com/open?id=1Y-KGw-IL2_nANx8E8zrJw_N8B_fsM7RB

Does this happen while rendering on the CPU or GPU?

It happens in both cases.

Can you share the .blend file with us? My bet would've been either a clipping issue or artefacts due to buggy GPU driver.

The denoiser would be another suspect.

I added the .blend file to the description. Turning off the denoiser doesn't seem to help :/

The problem first appeared when I added the particle system, so I made a render without them but the result was the same.

You have a (large scale) copy of the axe head in your scene that is hidden in the viewport but not in the render. Activate the restrictions toggles by clicking on the filter icon in the outliner, most importantly the Disable in Renders toggle (camera icon).
Toggled the viewport visibility (eye icon) to show the hidden axe head

Hide in Viewport, Disable in Viewports and Disable in Renders can be used to hide it an object both in viewports and renders.

That's it! Thank you so much for checking.


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Stretched textures in exported FBX file

Please Let me know what am i doing wrong and how to solve it,
Thank you in Advance.

This appears to be a limitation/bug in the FBX exporter.

Any other way to export my models to fbx perfectly?

let’s see your node setup.

Theres nothing in Nodes just a Image texture to base color, Image texture is a baked Diffuse map of a procedural texture.


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Blender Icing Render always white
In the rendering screen the frosting is the color it should be but when I press F12 it turns white. I'm not sure what the cause of it is. Can anyone help?
New to the website so idk how to reply. The add comment button does nothing. >_< My donut doesn't have a second icing object hidden or anything.
Added pictures for reference cuz idk how to explain it any better than I did.
https://gyazo.com/85c7104112ed116fcd49b01b064b342f
https://gyazo.com/e805f22e9d38911cc6c49d1ea6594e60 This is what happens when I press F12 to get it to render. Why does the frosting turn white???

Is there any chance you have a second "icing" object that is hidden in the viewport? Objects hidden in the viewport will still be visible in renders.

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

Added pictures for reference cuz idk how to explain it any better than I did. https://gyazo.com/85c7104112ed116fcd49b01b064b342f
https://gyazo.com/e805f22e9d38911cc6c49d1ea6594e60 This is what happens when I press F12 to get it to render. Why does the frosting turn white???

please just copy/paste pictures directly in your question. No need to use links. Please provide blend file, so we can check it out.

How do I upload a blend file here?

How to add a blend file

Hope this worked.

Hello and welcome. Instead of having users go through links and external sites please use the builtin tools to embed images in your post. See How to upload an image to a post? or GIFs

Will posting the images as embed files actually help me? Cuz I've posted the images as links, which means you can see it, but people are still stooped. If no one can answer can I be directed to somewhere that possibly could?

You have set a keyframe on the base color of the icing material. Therefore, whenever a frame update happens the adjusted value is reset to the keyframed value.
Right-click the color selection box and clear the keyframe. Then you can proceed as normal.


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Mesh looks fine in Edit mode but disappears in Object mode
Suddenly this anomaly struck, affecting only this model. I had just made the final edit of this model (snapshot 1), and was ready to save and export it. However, when I switched to Object mode, the mesh disappeared and other objects displayed in its place (snapshot 2). These other objects are used in Booleans to form the final object Back5, but they are not the Back5 object. If I select any one of those objects on screen, Blender indicates I selected Back5!

I've never seen this kind of behavior in Blender before. Don't know if I made a silly setting change. Perhaps Layers was involved - don't think so. Perhaps executable was corrupt - installed 3.6.5 - everything the same.
I'm baffled. Any ideas?

Hello could you please share your file? https://blend-exchange.com/

Thanks for your interest. Blend file added.

Maybe it's because of Boolean.001, it fails, you need to switch to the Fast option to make it work (or Exact with the Hole Tolerant option activated):

Many thanks @moonboots for taking the trouble to resolve this.

You're welcome..........    ;)

Many thanks @moonboots for taking the time to resolve this. What surprises me is that a Boolean can have such an extreme effect without the slightest indication of a 'failure', as you say. Have I missed some basic documentation not to know the Boolean had failed or could cause such an effect? Or could failing Booleans try to provide some error notification?  (Added this comment separately because, apparently, it took more than 5 minutes to compose .  grr  All caused by  a carriage-return which is natural for me to provide format but apparently verboten in Comments [it's been awhile] grr)

Generally Boolean works, but I'm not always sure why its fails with an option and works with the other. The old versions (that used the Fast algorithm) mainly failed when the edges of the boolean object and those of the booleaned object were overlapping. Now if Fast doesn't work, Exact generally does and vice versa, but sometimes you need to switch the exact Hole Tolerant option on


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Texture Paint Error in Blender 3.0
I don't know why but when try to use the texture paint mode it just doesn't work properly.
When I paint in the image editor the 3d viewport result gives me a color which is a mixture of the colors in the image editor and when I try to paint in the 3d viewport, instead of affecting the area of where I paint it affects the entire object like it gets a light layer of the color which I try to paint over the texture.
I am a beginner so it will be really helpful if location of where the diagnose this problem is also mentioned
(sorry for my bad English)
I hope these images help
Pic 1 is the base texture I have
Pic 2 is what happens when I try to do something in the image editor
Pic 3 is what happens if I click or try to do something anything in 3d viewport
Edit: Here is the blender file if anyone needs it:

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

Can you post the UV maps?

You can upload a blend file here: https://blend-exchange.com.

I think the problem results from using "color" in your brush options.  Probably if you switch to the first option, "mix" you will have different results.
Steps
Otherwise, you can run through some steps again:
Open the shader editor so you can clearly see what materials are being added, and click use nodes. Open the UV editor on the left  so that you can see where your material is mapped on the object.
In edit mode, unwrap the object by selecting the mesh and pressing U.
Then with the object still selected go to the Material Properties tab and assign it a new material.  Change the material color to make sure it is working. You should see it in your shader editor.

Now switch to texture paint and click on the plus sign to add a texture paint slot. This is your base color.   Complete the options, and you should now see an image appear in your node tree which you will be painting on.  Keep it selected.

With the new material selected in your node tree, and the image open in your UV editor you should be able to paint as you like.

I did everything you said but it didnt work.
I even created anoter similar object it still didnt work.
Apparently this happens everytime when i import a 2d object and then use it to make a 3d object.

That is strange. So this only happens with 2D objects?

yes and now just left it like that
(i didnt try it with other 2d objects but it only happened with this one which i did twice as a seperate object)

I tried with other 2d objects which I transformed into 3d, i finally noticed that when i try to paint it only registers to the faces the object had while in its default state, so when i try it with a square i can paint only on the top and the bottom not the sides, and since the circle had no faces it shows that problem

@XanderFalcon have you unwrapped the object like he said? In the file you imported, the object is not unwrapped and that explains the behavior from your question.

Yep I did everything he said

OK yep @mqbakamqbaka you were right i didnt do the steps correctly like he said, i am so dumb.

@common_goldfish, and everyone else, thak you for helping me


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Plot single vertices based on xy coordinates from CSV file
I'm aware there are numerous posts/questions already been raised on this, but upon reading the previous posts, I'm not quite able to find exactly what I'm looking for. So apologies if there's a duplicate post that already answered this.
Basically, I have a CSV file with 3 columns = x coordinate, y coordinate and pixel value (based on 255 greyscale). All I want to do is import this CSV file in Blender and plot the points as vertices, using python script. That's it. So if there are 3 points in the CSV file, I want those 3 points created/plotted in their respective xy coordinates as vertices in Blender.
I've seen examples of python scripts for adding mesh objects. But I simply want to plot the points given the xy coordinates in the CSV file, as vertices. Not add existing 3D objects/meshes.
This is the code I have so far:
import bpy
import csv

with open(r'file path\img_pixel_coor.csv') as csvfile:
    csvread = csv.reader(csvfile)
    for i, row in enumerate (csvread):
        print("i = "+str(i)+". row = "+str(row))

This prints:
i = 0. row = ['494', '216', '86']
i = 1. row = ['494', '217', '86']
i = 2. row = ['494', '218', '86']
i = 3. row = ['494', '219', '85']
i = 4. row = ['494', '220', '84']
i = 5. row = ['494', '221', '87']
i = 6. row = ['494', '222', '87']
i = 7. row = ['494', '223', '88']
i = 8. row = ['494', '224', '92']

The print is just to show what's in the file (logging purposes).
Also, would it be possible to put this script in a python file, and run it from a python file, without having to manually open Blender, i.e. can you control externally from a python file, to open Blender and run the script, without having to actually open Blender software manually yourself?
Any help would be greatly appreciated.
Update:
Here's a sample of how the CSV file looks like in the first few rows, to demonstrate how the x, y and pixel values are structured:

Finally, how do I smooth the vertices more. As you can see from the image below, the surface of the mesh is very spikey. I used the code below, but it's still very rough/spikey surface.
for p in ob.data.polygons: #Set smooth shading (if needed)
    p.use_smooth = True

Many thanks in advance for any help.
Illustration (my understanding):
of the code:
# Vertices store the color values as Z
vertices = [Vector( (x, y, int(z_max * random.random())) ) for x, y in product( range(x_size), range(y_size) )]

# Get base face indices
face_basis = ((x * y_size) + y for (x, y) in product( range(x_size-1), range(y_size-1) ))

# Each face is a square for the base index turning around counterclockwise
faces = [(v, v + 1, v + y_size + 1, v + y_size) for v in face_basis]

See here https://blender.stackexchange.com/questions/76535/create-model-from-xyz-data-points/76612#76612

Thank you for your response and referring your answer. Really appreciated. I have a question. In the code, I think it treats the 3rd column of the csv file, i.e. float(r[2]) as the z coordinates. However, the 3rd column, in the csv file, is in fact the greyscale pixel value (I think it's also referred to as the brightness intensity value) 0-255. So is there a way to plot this in Blender as such, rather than as the z coordinate?

Vertex colors in Blender are stored as face loop. That means you can not assign a vertex color if there is no face (nearly the same for materials). So here you'll need some rules to make it colored. Is for instance (x,y) map a regular grid?

Apologies, I'm a bit junior in Blender. I'm not sure if I understood your question correctly. I'll try to answer based on how I interpreted it. I'll show you a sample of how the csv file starts in the first few rows, so you can see if x,y map to a regular grid. Basically when plotting the data from the csv it forms into a rectangular frame. But the content on the inside of that rectangular frame I base it on the third column pixel value. Actually, looking at it, I'm happy to go along with plotting the third column pixel value as the z coor, as it provides the depth. However ...

I'm still wondering how to use the same third column (representing 0-255) to use its values as the material colours? I've update my question above to show how the first rows of the CSV look like in terms of x, y and pixel values. Hope this helps in answering your question.

Also, I updated the post with 1 final question I have, on how to smooth the vertices that form the surface of the mesh, as it looks really spikey. Is there a way to smooth the surface/vertices more? Please refer to the update on my post. Many thanks for your help so far. Really appreciated.

I suppose the input data is a 2D grid with known max values.
Here, we start with a random input but seeing your question you know how to load data from a file.
The script below does the following:

Create random inputs (you'll use file data instead)
Create vertices and store the color value as Z coordinate
Create the face vertex indices
Make a mesh object from that
Scale the object along Z
Create a vertex colors layer
Assign the Z value of the vertices as vertex color
Link a prepared material to the object

That gives the following result:

import bpy
import bmesh
from mathutils import Vector, Matrix
from itertools import product
import random

# Generate a random grid of the given file
x_size = 20
y_size = 30
z_max = 256

# Vertices store the color values as Z
vertices = [Vector( (x, y, int(z_max * random.random())) ) for x, y in product( range(x_size), range(y_size) )]

# Get base face indices
face_basis = ((x * y_size) + y for (x, y) in product( range(x_size-1), range(y_size-1) ))

# Each face is a square for the base index turning around counterclockwise
faces = [(v, v + 1, v + y_size + 1, v + y_size) for v in face_basis]

# Create resulting object
name = "grid"
mesh = bpy.data.meshes.new( name )
obj = bpy.data.objects.new( name, mesh )

obj.data.from_pydata( vertices, [], faces )

# Scale it along Z
scale = 1.0 / z_max # Or set 0.0 here
obj.matrix_world = Matrix.Scale( scale, 4, (0, 0, 1) ) @ obj.matrix_world

# Smooth faces
for face in obj.data.polygons:
    face.use_smooth = True

# Get or create vertex colors data of the given name
vcol_name = "VCol"
vcol = obj.data.vertex_colors.get( vcol_name )
if not vcol:
    vcol = obj.data.vertex_colors.new( name = vcol_name )

# Assigns z values as vertex colors
for face in obj.data.polygons:
    for vertex_index, loop_index in zip( face.vertices, face.loop_indices ):
        intensity = obj.data.vertices[vertex_index].co.z / z_max
        vcol.data[loop_index].color = (intensity, intensity, intensity, 1)

# Get the prepared material
material_name = "Material"
material = bpy.data.materials.get( material_name )

# If found assign it to the object
if material:
    obj.data.materials.append( material )

# Link the object to the scene
bpy.context.scene.collection.objects.link( obj )

The material is the following:
It uses the created vertex color as input for a color ramp and use this color for shading:

As your question was about plotting vertices, you may want to rework the mesh manually or modify the script to have this kind of results:

Note:
An illustration for
# Vertices store the color values as Z
vertices = [Vector( (x, y, int(z_max * random.random())) ) for x, y in product( range(x_size), range(y_size) )]

# Get base face indices
face_basis = ((x * y_size) + y for (x, y) in product( range(x_size-1), range(y_size-1) ))

Comments are not for extended discussion; this conversation has been moved to chat.


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Blender not showing whole images
Blender is not completely drawing images. The 3D viewport itself works fine, but many of the other features are not working.
I will begin by showing images of the issue. At the bottom I describe my settings and system.

For example, the splash screen only shows half the image.

This image has finished rendering (As visible from the saved image), but only a portion of it shows in the viewport. The second image is just the image itself, not a screenshot.

Finally, the node editor is missing images and even entire nodes.

I've attached my system settings if anyone has any ideas about what may help.
I am running Arch Linux under the Nouveau drivers. Everything is completely up to date. I've already looked at this thread, over on the arch linux forums, and the fix was to switch to the Nvidia proprietary drivers. Unfortunately, those drivers fail to run on my card properly (I've got a dual gpu card which is not correctly supported and so it only uses one GPU which immediately dies under the weight and shuts off the computer) so that isn't an option. Has anyone seen this and come up with a solution?
Thank you!

Yes, this is driver issue… You can try to tweak OGL settings in UserPreferences, System tab (change drawmodes, remove any multisample, etc.), but there is no guarantee you'll be able to get working this way.

The Nouveau drivers don't work for CUDA, you have to use the Nvidia proprietary drivers.

This older question, was  off-topic on Blender SE. Any answer will in longer be useful in any case,  so it  has been closed.

I had the same on a old Dell notebook with Nvidia Geforce GO 7950 and Nouveau driver.
I managed to get the full images shown by selecting DrawPixels as Image Draw Method in user preferences.

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


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Converting hair particles to only one mesh to avoid Blender crashing
I have a tree that is emitting 32,000 planes that are textured as leaves.  I need to get all of these to be one single object, however if I click 'convert' in the modifiers section, Blender becomes unusable by trying to create 32,000 different objects.  Is there another option or script I could use to convert a particle system to a single object?

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


text:
Blender custom point density from file
I'm scoping out solutions for rendering custom volumetric data that I'll be parsing from some external source (a simulation being run externally to Blender). I'd like to use Blender's volumetric rendering capabilities to render frames of simulation output by my program.
Here's an example of rendering some volume (in this case using particles as density markers).

I'm wondering if it would be possible to put my custom data through the density channel here, through scripting, etc. Maybe there's a way to script the positions of particles in a particle system? Thanks


text:
What is the workflow for compositing Fire/Smoke with Cycles
Since fire/smoke is currently only supported in the internal renderer, what are some good workflow ideas for bringing fire and smoke into a cycles scene.
My current idea seems too labor intensive:
Rendering out the Cycles frames, then duplicating the scene, setting the renderer to internal and changing all of the materials to masking alpha. Then compositing the frames together.
Is there a better way until volumetrics are added to cycles?

possible duplicate of Composite transparent overlapping objects from different scenes?

No I can composite 2 scenes no problem. The question is more about scene setup workflow. Having to have 2 sets of materials for the objects in the scene that will be rendered via cycles is a hassle.

thats simple prepare your animation in cycles with cycles material,duplicate your scene full copy,leave all cycles material on place put fire on place you need and render in BI cycles material will be ivisible and crate mask just set backround black and finaly composite both scenes

I was hoping to be able to easily link everything but the materials, that way I can still make tweaks to the animation/etc without having to completely redo BI sim stuff.

BTW, blender cookie made a tutorial on this recently

This looks pretty much like what you're looking for: http://cgcookie.com/blender/2013/10/10/compositing-smoke-simulations-cycles-renders/ (it's a free tutorial) Haven't tested it myself though.

Expanding on tobkum's answer, an example workflow using the technique in this tutorial might be:

Setup BI scene (simulation, etc.)
Create a new scene for Cycles, with Link object data
Create Cycles materials, linking to Object instead of Data so BI and cycles materials are not synced:

In the BI scene:

Create BI materials, again using Object instead of Data.
Disable shadows for all BI materials except the smoke
Create renderlayers for smoke and smoke shadows using the Shadow pass.
Create renderlayers for reflections and refractions, and remove sky by setting the Horizon color to black.

Setup compositing in Cycles scene:

Create renderlayers for foreground and background objects
Multiply BI shadows with cycles background layer
Alpha over BI smoke over cycles background layer
Alpha over cycles foreground layer over composite
Add or Mix BI reflections and refractions to composite

Render

As of version 2.73 it is now supported and has become much easier, see my answer here:
Rendering smoke in Cycles?


text:
Moving a Linked Library
Is there a way, after a library is linked to move that library to another location? I have a library that is in a different folder than my scene file and for the sake of more easily sending it to a renderfarm I want to move it all into one folder. Is there a way to edit link paths?

With the Project Glue addon, you can move library files and have the users be automatically updated to avoid broken references.

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - From Review


text:
How to rig two hands to item for RIGIFY

i want too connect both hands of my rigify rig to this sword, i tried the ik hands too weapon but i dont know how to do that for rigify, as which layer of bones too turn into ik or if even possible?

This isn't a great question ATM, because you haven't described what you tried when you say "only one can connect".  Probably the best thing to do is show your best effort to making this work in a linked file.

@Nathan i remade the questions now sorry, i was tired when i first made it : D

Have you tried a Child Of bone constraint for both IK hands bones (hand_IK.*)?

@Blunder when i do that only one hand at a time can be connected not both

There are 2 two hands, give each a Child Of bone constraint. Why should this not work? https://i.sstatic.net/OsIDH.gif - The "sword" is keyframed & has its own armature with just one bone. The shoulder is keyframed. The hands have the bone constraints and follow the sword.

@Blunder okay now i had understand just learnt about constraints

Ok, I just wanted to make sure we were talking about the same thing. There are bone constraints and object constraints. Don't confuse them. The bone constraints can be added in Pose mode, one for the bone of the left hand and one for the bone of the right hand.

Let us continue this discussion in chat.


text:
Auto smooth shading problems

With auto smooth on, the shading is weird

without auto smooth , its clean

you should show us your topology....

could you please share your file (the part you show only): https://pasteall.org/blend/

try to make a mesh with all quads.

@XY dont be hating on the triangles :)

In the Object Data Properties panel, under the Geometry Data tab, try using the Clear Custom Split Normals Data.
I am still not sure what it does, but it works for me sometimes.

Hope this helps !

It removes any custom normals data.  The normals for faces are usually calculated from the geometry of the face, so that they just point outwards - but blender is happy to let you overwrite them with normals pointing in arbitrary directions.  Typical sources of this include using the bevel command with Harden Normals, applying a Weighted Normals modifier, painting the normals or really anything that manually or automatically modifies normals!  Clearing it like you suggest resets it to calculated from the face and edge angles.

Aahaa ... I didn't know here were so many ways to override the normals directions! Thanks a lot for the clarifications... :)


text:
Rigify tail bones doesn't generate controls

I added tail bones too my characters clothes but they do not generate controls, only the body does.
I just got tail bones put them in place and paired them so what step am I missing or is there a better way too do it?

You need to tell Rigify that your added tail bones should be a tail. This is done by setting the Rigify Type to spines.basic_tail for the base bone of the tail. Then it will generate the control bones for the tail as you can see in the screenshot below.


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Bad auto weight paints

Why are these rigify auto weight paints so bad. Other parts of the body work fine, i didnt have this problem before with the same model

The normals are flipped on the pants. You need to turn off the Solidify modifier to see it.

To fix it switch to Edit mode, select the legs (L), and flip the normals (Alt+N Normals > Flip). In Object mode, consider to apply the scale to the model (Ctrl+A Scale). Rebind the mesh to the armature.
Last but not least, make sure the Solidify modifier is added after the Armature modifier so the Armature modifier uses the original mesh to deform.


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Basic Topology, curved square
Relatively new to blender, but at the minute I am trying to get my head around good modelling and topology. I'm using some basic models as a reference and then trying to recreate lighting, materials, and modelling. I have attached a reference for what I'm trying to recreate, but struggling to create the square without getting artifacts that are effecting shading and the basic shape. Included is an image of where I have the topology now, and also an image of what seems like it would work best for adding a bevel to edges
Any help or advice for how to get the modelling correct is appreciated

what about this:

create a cube and tab into Edit Mode then press SZ to resize

select these edges (edge selection):

press Ctrl+B and mouse wheel up

then add Bevel Modifier + shade autosmooth

Perfect, no need for quads :). I'd perhaps check Harden normals, but that's just nitpicking :))

I would add a single inset faces to that quad, after which the ngon will be perfectly planar with its neighbors, preventing any smooth shading or c-c subdivision artifacts.

Thanks for your supportive comments!

Thanks so much for this, I think I'm missing a step somewhere to get to the last images topology, I have followed all the above steps, not working, then I have tried to apply the bevel modifier or go into edit mode and ctrl+b the edges, auto shade seems to do nothing, its obviously something simple but I am definitely missing something here, thanks in advance, I was so full of hope when I saw the replies but stuck again

ok, pls make a video of what you did so we can see what you did and correct you. Or really describe step by step what keys your are typing and what menus your are chose.

@StephenKenny hi the link you added in your edit suggestion does not work. perhaps because you need to be logged in so i removed it.

Apologies for delayed response, super busy with work, I can't seem to upload my video, but the steps I have taken are

Resize cube, S+Z
Edit mode, select each corner edge as displayed above
Ctrl+B to bevel width .2m and 5 segments
Shade smooth, Object data panel, normals, shade smooth at 30 degrees
Object mode, add bevel modifier (amount 0.024) (segments 5) (angle 30degrees)

I feel there is a step missing after this?


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Object shadows having lines doubled

The shadows of the objects seems to be doubling up and even when moving the object around it flickers.
Eevee

Cycles

How many lights are you using? There is a shadow for each light you add.

In this object there's three lights added, but when I try even one light it's still the same. In Cycles render engine it looks good but when I switch to Eevee it does this multiple shadow thing, both times in single areal light.


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My mesh is grey and I'm not able to paint it
I'm new to Blender and had probably pressed something wrong when painting the mesh but it has some grey structures on top of it and doesn't allow me to edit it in texture painting.

See https://blender.stackexchange.com/questions/122965/cant-paint-textures. Seems Face Selection Masking is on in your case

Also looks like you have two other "sphere" objects overlapping the object you want to paint, and all are visible at the same time


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2.8 Glass not reflecting in mirror?
I'm new to Blender and modeled a glass lantern and mirror. For some reason, my glass is not reflecting in the mirror and the reflections in the mirror are lower in resolution. The glass lantern and mirror are simple materials I have made in the node editor based off of a few tutorials. I appended other glass models into my scene and the mirror seems to reflect everything but glass.
How can I make my mirror reflect details accurately? Why do glass objects not reflect in my mirror? Also, how do I conceal the shape of my area lamp in my final render without hiding it because it reflects in the mirror?

Please help me figure out what is going wrong.
EDIT:
Here is the blend file with reflection plane:
mirror_lanter_bulb.blend

Unfortunately, the glass bulb inside the glass lantern is not visible at certain angles. May someone know why?

EEVEE supports reflection by having a map that saves a screenshot of reflection.
You can add a reflection plane in front of your mirror. Also, the reflection setting in both the material settings and in the main render panel should be checked.

And the HDR 360 image is already a map, so it is always there by default.

I added the reflection plane and it worked like a charm. Thanks! Now onto why the glass lantern isn't reflecting and how to conceal the area lamps.

Basically you have forget to enable Screen Space Reflections and Refractions checkboxes, but it not necessary with Reflection Plane.

Currently Eevee couldn't reflect refracted surfaces.
For correct mirroring use Add > Light Probe > Reflection Plane:

Result download:

Glass node setup with Camera crutch.
Blend and Shadow Mode could be Clip or Hashed.

Reflection Plane rhombus should be on minimum distance as possible by view look. On right side you can see my settings.

This suggestion worked like a charm. Thanks for helping me get my mirror to reflect the details better.

updated my answer, have to write more, but time not enough...

The node setup that you suggested certainly worked in reflecting the glass objects onto the mirror. But now, the glass bulb inside of the glass lantern is not visible at certain angles. Do you know where I may be going wrong? I updated the blend file in my post above and included a screenshot of the different angles. Thank you for your help


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how to extrude neighboring vertices without creating a face in between?
As in question. Check the picture. I do not want any faces inbetween.
Kind regards.
Please see the picture:
1) - original
2) - after extruding using E (+Z)
3) - after 2) and deleting the faces (not what i want)
4) - after using Edge -> Extrude edges (as in answer below) -> That is what I want, sorted. Thanks

You can always delete faces and keep vertices or edges ... post facto.

Control Click can add vertices without faces.

It's hard to figure out what's your goal from one picture. Could you upload another to show what you want to achieve?

You may also want to show your question in edit mode with a highlight.  This would improve readability.

use CtrlV to get to vertices menu, then extrude vertices will extrude only the vertices.

You may also context click for the same menu.  That might be considered very 2.8 style for edit mode.

worked, thanks, I have also precised the question.


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Shading on wrong face
Im new to 3d. Ive modelled a house and now trying to texture it, however the texture is showing on the wrong face for all the walls! So many hours I have put into this, I have no idea why the shading is wrong. The shading shows on the bottom face. Is there a way I can fix this? I created a new cube just to see whats going on and it happens to the cube too. Thanks.[![wrong face][1]][1]
EDIT: I added texture coordinates as suggested, but i now get wierd buckling on the shader. I tried adding a subdivision surface modifier so the shader would work better, but made no difference, so i deleted it. in fact it made the edges all distorted or made no difference on other objects.
It may be due to unwrapping or my seams?

Or is it due to how i cut a hole using knife project which has resulted in endgons? Whatever they are :)

All of this is just a mess and confusing!!

Thank you Josh, you have been very helpful, this has fixed the mapping, hoever Im still getting pinching on the surface? Any idea what this would be?

By default textures are shading both sides of a planar face, but this is not what you're experiencing here.
Problem is that by default texures different from Image Textures (like your brick texture) use "Generated" Texture Coordinates, while you probably should use UV.
So, to solve add a Texture Coordinate node and plug its UV output to Vector input of the Brick texture.
If still in trouble check if your mesh is properly UV Unwrapped (but this will work on the default cube, which is always already unwrapped).

As the mesh is composed by big uneven N-gons, there will be uneven distorsions along borders of N-gons faces (this is what we call "Ugly topology").
To solve, you can select one face of a plane, press Shift G (Select similar > Coplanar), then go to the Select Menu > Select Loops > Select Boundary Loop, press Shift E (Edges Menu > Mark Seam), select again all surface, go to front ortographic view and press U > Unwrap > Project from view.
Repeat for the others surfaces.
When finished go to UV Edit window, select all, UV Menu > Pack Islands + Average Island scale, then rotate all 90 degrees if needed.

Thank you @joshsafanfelici I generated the texture cordinate which did the trick but now the shader looks nuts as you can see above where i edited my initial post.

I updated my answer.

Thank you Josh, as you can see above im still getting pinching. What could be doing this?


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Out of memory on render despite enough space avaible
I am trying to render a small scene using cycles on a cluster. The operating system is Linux and the Blender version is 3.1.3. The avaible GPU is an NVIDEA RTX 2080 TI and avaible ram 117 GB. Although the scene only requires 256 mb in memory it crashes when rendering the first frame. The error message reads

Malloc returns null: len=134217728 in Cycles Alloc, total 58075672
Error: run out of memory!

The error occurs both for CPU and GPU rendering.
I am looking for a way of fixing this error or at least diagnosing where the problem exactly lies.

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

I edited the question in order to clarify the problem. Kind regards

How do you know it requires only 256mb of memory? Many things in Blender have separated settings between the viewport and render for performance reasons. Maybe check what objects are disabled only and viewport and not in render, also check your modifiers if some are enabled in render only, especially your subdivide modifiers that can have different subdivision levels. You can also check your particles systems. Finally, you should probably also enable the Simplify panel in your render settings and drastically reduce the render options, just to check if it helps.

https://docs.blender.org/manual/en/2.79/render/blender_render/optimizations/performance.html


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Grease Pencil Object Transparency - Not Respected between Objects
I'm having an issue with Grease Pencil in Blender 3.0.
I have a grease pencil object with transparency, that intersects with another grease pencil object. (A creature standing in water). The transparency is shown on all other objects in the scene, so you can see through the water, but on the other grease pencil object (the creature) it just cuts off the image where they intersect. I've included a screenshot to illustrate the issue.

The issue is also present if I use a standard 3D object as the water, as shown below.

Has anyone come across this before, and has any advice on how to resolve this?
Thanks in advance.

Solved, it was a mesh issue on the ground plane extruding past the Grease Pencil object.
Tested transparency in a new document with just some simple objects and it worked fine, went back to this and removed the modifiers and the clipping stopped.


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Particle Sim does not look the same in render as in viewport
I'm trying to make a smoke effect, but some portions of the smoke just aren't appearing in the render. I created a mesh object cloud for the simulation to be rendered to, along with a wind field pointing upwards to simulate smoke being generated into the air, and duplicated both to go on both rear tires of the car. I baked all dynamics, but in the render, the "smoke" mesh seems to not have a trail like in the viewport. It sort of sticks to the tires. I also enabled Disk Cache but it didnt do anything regarding the problem.
First picture is the viewport of what the smoke clouds should look like in the render. Second picture is what I'm getting when I render the same frame.

Blend file:

i know you are new here, but maybe you can understand that just 2 pictures won't help us to help you.  So please provide provide blend file so we can check it out and so we are able to help you, else we can just guess.

Did you bake the simulation? Sometimes Blender messes up particle (and other) simulations if they are not baked before rendering, because it loses information between frames.


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Bug with particle simulation
I want to make a render of a car drifting, with the smoke emitting from a mesh parented to the rear tires. There are also wind force fields parented to the car to make the smoke-mesh rise up into the sky as it is emit. After baking, the viewport looks like this:

But after rendering, the smoke looks like this throughout the animation:

I've messed around with the wind and physics of the smoke mesh but I believe it is a problem with the rendering settings since the animation looks completely different in the render than in the viewport. Please help.

I think the problem has to do with your baking. Try baking all dynamics and also play around with the wind force fields because their strength might also be the issue.


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Flush python output in Blender 3.0
I have a long running script and would like to be able to see some form of progress indication - a simple print statement would do. From How to show to the user a progression in a script? and https://stackoverflow.com/questions/230751/how-can-i-flush-the-output-of-the-print-function-unbuffer-python-output , I have tried:
import sys

print(msg, flush=True)
sys.write(msg)
sys.stdout.flush()

My script is creating objects based on the contents of a CSV file:
import bpy
import csv
import sys

csvfile = open('c:/temp/input.csv')
inFile = csv.reader(csvfile, delimiter=',', quotechar='"')
# skip header
inFile.__next__()

i=0
for row in inFile:
    if row[0] not in bpy.data.objects:
        size = 0.0002
        x = float(row[0])
        y = float(row[1])
        elev = float(row[2]) / 10
        z = (elev / 2) * size
        bpy.ops.mesh.primitive_cube_add(size=size, enter_editmode=False, align='WORLD', location=(x, y, z), scale=(1, 1, elev))
        materialName = "ourMaterial"
        obj = bpy.context.view_layer.objects.active
        obj.active_material = bpy.data.materials[materialName]
        msg = "%d: %f, %f, %f, %f" % (i, x, y, elev, z)
        print(msg, flush=True)
        sys.stdout.write(msg)
        sys.stdout.flush()

The output does not show in the Blender System window (Window->Toggle System Console).
Is there something else I need to add to the script to pause execution for the output to flush?

instead of time.sleep you can use application timers to buffer between iterations. I've never had to use flush for printing things in the system console

Thanks @Gorgious, your comment that you've never had to flush got me thinking if it was the way I was calling the script... It works from the built-in text editor. Will post an answer with the details!

Solved thanks to @glorious. I was calling the script from the blender python console with:
filename = 'script.py'
exec(compile(open(filename).read(), filename, 'exec'))

If I execute from the built-in text editor, all is good :-)


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How to use Texture Influence with Particle System size
https://i.imgur.com/XrfZgeZ.mp4
I’m trying to use a blend texture with size influence on my particle system. I want my particles to start small and then big over their lifetime.
As you can see, the cutoff moves as the animation goes. I don’t have any keyframed values.
I’d like the cutoff to be fixed relative to the emitter. How can I achieve that? What am I doing wrong? Thanks!

Maybe instanced object itself have some animated scaling...

No, they have no scaling. I have no keyframed values

Could you send a file?

What happens if you delete the bake and turn off the effectors?

Uploaded a blend file.
When I turn of my effector and rebake my simulation, the texture works properly. However I need that effector...


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Warning when applying modifier via Python?
I am creating an icosphere and subdivide it.
When I do it in the GUI console, no warnings.

However, when I put these code into a script and invoke it by blender --background --python ..., I get the following warnings.
warning DM_ensure_tessface: could not create tessfaces from 240 polygons, dm->type=2
warning DM_ensure_tessface: could not create tessfaces from 960 polygons, dm->type=2

What does this warning mean?

No errors here. Make sure that the context is set to Object Mode and save the file:
import bpy

# set context
bpy.ops.object.mode_set(mode='OBJECT')

# get active object
target = bpy.data.objects['Icosphere']
bpy.context.scene.objects.active = target

# apply modifier
bpy.ops.object.modifier_apply(modifier="Subsurf") # apply_as='DATA'

# save the file
bpy.ops.wm.save_as_mainfile(filepath=bpy.data.filepath)

Command line:
blender -b <path-to-blend-file> --python <path-to-python-script>

I tried setting context to Object Mode, but the error seems to persist?


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Why so useful functions are not in official build?
Why so useful functions are not in official build:
Bevel node in cycles:

Apply properties disabling in Apply scale:

These functions have been implemented for a long time. Relay, are these functions so dangerous that they can not be included in the build? Or are they not included for another reason?

For one reason or another they are not considered stable or complete enough for general public use, so to avoid endless bug reports and potential work loss they are removed from view from less advanced

Not enough people, not enough time, personal preferences...

Also, (not in this case) many features are too specific and it is a better decision to leave them out so only people who want those features will have to deal with the bloat of space and speed.

I'm voting to close this question as off-topic because it is about software development practices, not Blender.

@JakeD ok, close all questions with tag 'development'

@Crantisz From development tag description: "does not include general programming questions"; this question is about software best practices and why the Blender Foundation chooses to develop the way they do, not a "coding question about addon or script development, and the Python API". At best this is an opinion-based question that does not belong on BSE. I don't think that you will get any more of an answer than the first 3 comments from Duarte, brockmann, and I.


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How do i merge a moveable part of an object?
i'm quite new with blender, so pardon me if this question is trivial.
I'm trying to import this model to vrchat and realize that the pauldron part is actually separate despite being the same object.
So, i don't need it to move separately and want to make it merged as one. How can i do it?[![enter image description here][1]][1]
Edit:
i'm sure my words earlier made some confusion, what i meant is i want to make this part of the model to keep attaching when move. how can i do it?
https://cdn.discordapp.com/attachments/434777529677774869/622668359787479060/ezgif-1-ac95a637266d.gif

Not sure I understand your problem. You can merge multiply meshes by selecting them and hit ctrl+j, but you can't merge an armature with a mesh object.

i'm sorry if i made a misunderstatement, what i mean is i want to make this part of the model to keep sticking when the body move.

It's not because that mesh is a separate object, that's because your weights are wrong. You can fix it with weight painting or assign the omious verts to the bone's vertex group.

Are you talking about the bones being separate? Because you only have one object in your hierarchy.
If you're talking about the bones you can go into edit mode, select the ball on the end of each bone you want to connect and press F to create a new bone between them.

i'm sorry if i made a misunderstatement, what i mean is i want to make this part of the model to keep sticking when the body move.


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Newly created edge from boolean or cut operation left selected or marked. Function or feature?
Is there anywhere a function, built in or not, that will mark (user defined) newly created edges, or leave the newly created edges highlighted for me to then mark or manipulate, if: The edge was made using a knife project cut, a slice operation in HOPs,  a bool tool cut, a carver operation, etc...? I see many ways this could be used. it seems like it should already be an operation option already and i feel like i'm missing something fundamentalobvious. Any insight or direction to point me in would be appreciated.

You could assign to a new vertex group (Ctrl G), you could mark as seam (U)...

Thank you for responding but its not what to do with the selection. Its how do have those selections made for me upon cut operation. Manually having to go back and select those new edges is what i'm trying to avoid.

of course, you need to save or mark as soon as you've created the edge

Should i be expecting the edges say, of the knife cut or bool cut to be highlighted upon operation? i've been wondering if i'm crazy and thats the way it normally works and just isn't doing that for me now

If you cut with the knife for example, the new vertices are selected, you can either save as a vertex group or mark seam, but I've never heard of being able to select them automatically afterwards if you've not done that

Then my blender has stopped doing that for a while and i'll have to troubleshoot. Its been one of those things where i thought it was a thing and a thing i've used and didnt think about it. but now its gone or was i just remembering wrong? i asked around a few places and no one said Yes, it should already do what youre asking about. As far as doing things for me thats nbd. If the vertices are selected for me, thats the actual time saver. Marking or assigning or whatever would just be extra whatever

See: https://zupimages.net/up/23/37/5noh.gif

thank you for taking the time to show me. There's so many things this program does, it has been one of those things where i thought my memory was just faulty. i'm still curious about the other cut modes leaving vertices selected but until i get a simple knife cut to do it I don't know expected behavior. i'll troubleshoot. I'm glad i posted here. We can mark this mystery solved, case closed. thank you!

That said a boolean won't let the carved surface selected    ;)

okay. i was in face mode when i said that wasnt working. Still, this tells me i need to be more critical in my assumptions. I may have what i need and i'm just doing things rong

Marking for me is something i could prolly just build and a "nice to have". Its the selecting of the edges after a bool cut or HOPs slice cut that is valuable. For the bool cut to behave like the knife cut, with the edges selected after being applied. I'm using bool tool and after cut in vert or edge select mode they are not selected. Knife is doing it for me as it is for you.

If you cut with the knife for example, the new vertices are selected, you can either save as a vertex group (CtrlG) or mark seam (U), but I've never heard of being able to select them automatically afterwards if you've not done that. But if you use a Boolean modifier for example, the carved part won't be selected.

For the Knife tool, see the answer from @moonboots and for the Boolean modifier: well, before the modifier is applied there are of course no new vertices/edges selected because they are not yet created.
If you want to apply the modifier and mark the newly created vertices or edges as seams or put them inside a vertex group, there is no real automatic way of doing it, but a kind of workaround, you have to do two things before applying the modifier:

The object that you want to be cut needs to have no vertices selected in Edit Mode.

The cutting object needs to have all vertices selected in Edit Mode.

If you now apply the Boolean modifier and go into Edit Mode on the new object, all new vertices from the cutter are selected, while the original ones are not. Now you can either assign them to a vertex group with Ctrl+G or mark them as seams with Ctrl+E > Mark Seam or U > Mark Seam.

I knew the cutter's UV map and other properties are transferred, but I have no idea it even works for selection!


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Blender Object loses Alignment during Rotation (Only During Render)
I have a blender object which animates / rotates along the z axis just fine in the viewport:

However, when I render it in either Eevee or Cycles, the object (hilariously) loses alignment and breaks apart:

Can anyone help me figure out what's the cause of this really strange behaviour at render time?
Edit: deleted all my rendering configs.  Issue was caused by original object overlapping with my Collection Instance and showing up on render. I had to hide the original object in order to make it work on render.
cake model comes from here

Does this object have any render-time displacement?

I'm not sure.  I don't believe so.  I've attached my additional settings from different screens in the original post.

this is where I got the original cake model and brought it into my own scene: https://www.cgtrader.com/free-3d-models/food/fruit/desserts

It seems like you have two of these objects in the Scene, and the second one is disabled from viewport visibility, but not rendering.

... model on the provided link is OK, also you can delete your huge screens of render setup, they have nothing to do with your issue.

@vkliidu might be onto it.. make sure you have no objects hidden in the viewport, but visible to the render.

Yes!!! Thank you vklidu and Robin Betts!  It was showing my original object + Collection instance and overlapping them. I have edited my original post.

Issue was caused by original object overlapping with my Collection Instance and showing up on render. I had to hide the original object in order to make it work on render.


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How to disable in render just one object and not the entire collection in blender 2.8?
Earlier in outliner 3 options were available for each object one of which was disable render. Now only one option is available for each object. Basically how to disable render for single object inside of collection

In the outliner there is a filter option which allows you to enable the Restriction Toggles that aren't displayed by default which includes Disable in Renders (camera icon). Once you have it enabled you can disable any object or collection from being rendered by clicking on the camera icon behind it in the outliner.

Thanks rjg .. I was wondering why they will remove it..

@PrashantKumar You're welcome. They wouldn't remove such an important feature. I currently can't find the discussion on the patch or commits that introduced hiding the restriction toggles by default, but I'm assuming it's to reduce the number of icons in the UI when they aren't needed. This change has confused a lot of people since it was introduced.

Another way is to make this object one hundred per cent transparent.


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Copying linked objects along with animation
I am new to Blender and I managed to educate myself on how to animate objects.
I have animated how the module below gets deployed.

Using the same deployment strategy, the module needs to be multiplied to create a large formation like in the picture below.

When I copy one module along with its animation, the animation fails to animate the copied module. At the end of first module animation, I want the second animation(copy of the module) to start. At the end of second, third starts and so on.... How can I execute this without manually creating animations for every module?

What is the way you are using here to animate the base module? (as it is mechanical there is not one possibility)

As the central connector is pulled up, the vertical and horizontal members loosen and collapse. I have added  2 images to show what I mean.


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Items are invisible when they are created
I'm posting this for a friend. We are using blender 2.81
While doing the dount tutorial from Blender guru at the end of level one he couldn't move the object anymore. After reloading the program the problem was fixed (didn't know about load factory settings yet). But a new problem (well we weree juping from problem to problem but this is the last one) arised the items that create are invisible until
(We made a recodring but sadly i don't see a way to add the video. So i will just send a picture of how it looks when the object spawns.)

he clicks this
 and the object apears(stopes being invisable).
If anyones knows how to fix this or if this is a setting how to turn it off please tell me.
Aditional info:
-loaded projects work fine
-we tried laod factory reset
-we had similar problems (multiple problems were noted before) but they went away and we    are stuck with this

Please, try to be a bit more clear when asking you question! Sharing your .blend file would be a great help as well.
Also, you may not know that 2.81 is currently in Alpha, so it's unstable: try using Blender 2.80 until 2.81 is ufficially released

I presume it's a 2.81 thing, but i wanted to check.
.blend file doesn't matter sicne it's a newley created file and he jsut added a new shape and it became unvisable until he clicked the icon on the second image.
The main reason why my friend want's to stay on 2.81 is beacus of the feture that get's rid of sound(i belive it's called that, when you zoom into the picture and it's distorted) in the picture.
I'm not sure what is unclear if you can point it out i would be very greatfull

I opened Blender 2.81 (17/09 build), and in the startup project I created a new cube and a new sphere. As you can see from the screenshot, they are both visible in solid and rendered mode.

The icon you posted seems the icon near the object's name in the outliner, and by clicking that you simply toggle bewteen object mode and edit mode

Are you sure there are lights in the scene?
A .blend file or more precise instructions on how to build your scene would be appreciated.
Also, make sure you have the latest build of Blender 2.81: maybe your specific version had a bug that was fixed in future version

I guess the problem was somewhere in his files. since today he reinstaled it again and it works.
Thank you to those who took the time to tr and help


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How Can I Achieve This "image bleed" Background Effect?
I am new to blender and I'm trying to figure out how to get objects and images to bleed onto a background.
Video E.G.:
Look at the background and how objects are being printed onto it
I accidentally did it in a project while messing with the world shaders, but at the time I did not need to do it and now I can't seem to replicate the effect.
If anyone has any ideas please share them with me!

I don't know in Blender but in some other applications it is an "Echo" effect.

See https://blender.stackexchange.com/questions/127612/is-there-an-echo-effect-for-animating-in-blender


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Script to replace all materials linked to the a given texture
New to Python / blender API here. Here is the process I'm attempting to script after having manually selected a material from the active object:

identify texture
find all other materials in scene using that same texture
replace with selected material.

update : found the solution, problem was about the API changes in Blender 2.8.
(original issue) I'm stuck at step 1: I can't find a way to tell the API: "please get me a pointer to the active material's texture".
Is this possible?
Thanks in advance,

Ok, the following script does a bit more. See comments - disable "renameUVMaps" if you don't plan to join the meshes. Useful to rename the UV of identical textures so that mapping data is kept active.
import bpy

# Options
renameUVMaps = 1

# 1. Get the "active texture name"
activeObject = bpy.context.object
activeUVMap = activeObject.data.uv_layers[0]
activeMaterial = activeObject.active_material
activeTexture = activeMaterial.node_tree.nodes["Image Texture"]
targetImageFilename = activeTexture.image.name

print('Material %(materialName)s will now replace materials using texture %(textureName)s' % { 'textureName' : targetImageFilename, 'materialName' : activeMaterial.name})

# 2. Loop through scene objects and replace materials with the selected one (when the texture file name matches)
for obj in bpy.context.scene.objects :

    # 2.1 Re-assign material
    for slot in obj.material_slots :

        thatMaterial = slot.material
        thatTexture = thatMaterial.node_tree.nodes["Image Texture"]
        thatImageFilename = thatTexture.image.name

        if targetImageFilename == thatImageFilename :

            if activeMaterial != thatMaterial :
                print('Obj %(objName)s -> replacing %(materialName)s in slot' % { 'objName' : obj.name, 'materialName' : thatMaterial.name })
                slot.material = activeMaterial

            # 2.2 Rename UV Maps for joining
            if renameUVMaps == 1 :
                if hasattr(obj.data, 'uv_layers'):
                    layers = obj.data.uv_layers
                    layerCount = len(layers)

                    if layerCount > 1 :
                        print('!!! Obj %(objName)s -> has more than 1 UV layer' % { 'objName' : obj.name })

                    if layerCount == 1 :
                        uvLayer = layers[0]
                        if uvLayer.name != activeUVMap.name :
                            print('Obj %(objName)s -> renaming UV layer to %(targetUVMapName)s (was %(previousName)s)' % { 'objName' : obj.name, 'targetUVMapName' : activeUVMap.name, 'previousName' : uvLayer.name })
                            uvLayer.name = activeUVMap.name

print('Done.')


text:
Texture Painting on image is not showing up in Blender 2.8
I am a beginner to Blender. Currently I am following Blender Guru's Donut tutorial. When I tried to do the texture painting , color on the image is not showing up.

If I zoom in very hard then only the color is showing up.

And another problem I am having is event if I am drawing white color in the model some greyish color is getting painted. (I am not sure whether both problems are due to same cause or not).
Please help me out.
Here I am attaching the blend file and the texture files
Drive Link For Blend File

can you post the .blend? https://blend-exchange.giantcowfilms.com/

Looks like you are using a cloud texture as a brush mask, but that your brush color is white. Are drawing into the brown to be brown, or are you trying to get white instead? Check your tutorial, but you might be looking for changing mix modes on your brush and you might need to paint on a new image if it is to be a bump map instead of color map.

I have added the link to blend file . please have a look

The reason that the colour is not showing up is because your image is being obscured by the UV mesh of your model which is crazy high resolution. In order to disable it go to View and uncheck "Display Texture Paint UVs":

The reason your whites are showing up as grays is because of how light works, your model gets shaded and will only display at full brightness under very strong light (which won't show in deafult Viewport Shading mode). It's normal.
In order to see the true colours on your mesh you can select flat shading for your viewport:

Also I would highly advise disabling your subsurf modifier for your texture painting, my God that donut mesh lags out my pretty decant laptop. I don't know what kind of PC you have but I'm almost sure you'll get a better expirience without the subsurf on.


text:
How do Power and Strength values correlate?
When creating a non-light and giving it an emission shader, what values of "Strength" are equivalent to given values of "Power" in an area light?
Not a duplicate of Understanding light power values. This isn't talking about options in lights, but options in emission shaders that aren't lights on their own.

Related: https://devtalk.blender.org/t/cycles-unit-of-light-energy-attn-brecht/12456

I did some testing. You can use this as a reference sheet :).

Power : Strength ratio is 10:2,5 (for 1m² area)

Area lights use Power (W), Mesh lights use Strength
Mesh light used - default plane with Emission shader

Intensity and size relationship

Area lights - maintain their intensity with increased size.
Mesh lights - increase their intensity with increased size

Power:Strength reference sheet

I tested these as 4096x4096 images and still couldn't tell the difference.
Sorry for the color banding and compression artifacts.
Noise is a tiny bit higher for Mesh lights.


text:
How do I add together two a⨯a images to a single 2a⨯a image in the compositor?
I've tried using the translate node to move each image a/2 px left or right, but it cuts off the image.
To illustrate, here's an image:

Are these images or render layers?

render layers i guess

different scenes with different active cameras

What are you talking about? Could you please edit the question and clarify what you mean, provide some context maybe and add some pictures. It's unclear what the problem is and what your goals are.

If I understand correctly, you have two square renders of size a, and you are trying to composite them side-by-side into one image of size 2a by a, is that correct?

yes that's correct, see illustration

related https://blender.stackexchange.com/questions/52231/rendering-a-stereoscopic-image-in-blender-2-77/57870#57870

I suggest a different solution:
here's the Compositing setup:

The first node (image node) is an empty image (generate in blender as 100% alpha image) with the full size of your output image (1024x512). When the alpha image is added to the rendered image, the output (file output) is a 1024x512px file.
Add the second scene (again translated in the opposite direction) and you'll have the two renders aligned.

This approach is much better than my answer. Will the Composite output also stretch to the dimensions of the generated image, or does that only work for file outputs?

only file output (as far as I tested).

Thank you very much! Can I make the empty image in blender?

image node, new, than follow the screenshot:
https://i.imgur.com/J4FG4Uq.png

This is a bit of a hack and requires you to change a camera setting, but it gets the job done:
Create a new scene and set its output resolution to something with a 2:1 aspect ratio (such as 1024x512, if the original images are 512x512). Add the two inputs as Render Layers.
The issue here is that when you render, the two images will be rendered with the same aspect ratio as the current scene (2:1) instead of the aspect ratio of the scenes they were created in (1:1). To get around this, we have to render the inputs twice as wide as the output results will be (because parts of it get trimmed off), and trim off whatever's left.
Set the cameras to be exactly 1/2 the original focal length in the camera settings in the properties panel. (Ex: if they were the default 50mm before, change them to 25mm).

(The image shows both the original and new focal lengths, for clarity.)
Rendering these from the new scene will crop off the top and bottom edges when it changes the aspect ratio. Then, in nodes, you can translate them as necessary and combine. The Box Mask node crops the left side of the topmost image so it doesn't overlap with the one next to it.

(Here you can also see that the top and bottom were cropped off, hence why we needed to increase the focal lengths)
Result:


text:
Create a Material using Python script
I have Created a Node group Using Python Script and Now I wan't is To Convert This To Add-on,
I Wanted that whenever I click a Button "Add Test Material",
It Create a Material which consist of That Node group
When this Script is Run It Appears in Physics Panel,
Can anyone Help me Out How to do that ?
This is the Script which is similar To My Script - Python Script(Link to Google Drive)
My Script is Having following errors -

Node Group is Added But it is Not Connected to Material Output, how to connect this to Material Output Node.
When I Click Add "Test Material" Button in the Physics Panel(here this script appears) it should add this material to node editor but material is not added
but if i just re-run the script the material is added

Can Anyone Rectify this Script
I will be Very Glad If My First script becomes Successful as I am Noob to Scripting in Blender.

More effort please. Also, please post your code. BTW: the answer is simple once you understand what an operator is, read: How to create a custom UI?

I have Edited this Question to make it more Clear Please help me now, I need Help


text:
How to create a Low lying fog in fields slowly rising up?
I wan't to create a Meadow Scene and there is a lot of low lying detailed fog that is moving and rising very slowly like these in reference pictures
If I adds simple principled volume shader it will not have such details like this mist is rised to some level or height in picture 1 after that it disappears
Mainly Picture 1 is the correct reference picture for the result what i want

how can i create that can any one show me the node setup ?

https://blender.stackexchange.com/questions/43600/low-lying-fog-bounding-object-rendering-as-solid

Let me Add some Reference Pictures in this question so that question is clear

if you want to use a very simple trick you could just create planes with gradient effects which mixes Emission and Transparency and give it a bit of noise


text:
How can I Import Houdini Pyro VDB Cache data to Blender
I wan't to Import Pyro simulation from houdini to Blender
I tried to import VDB cache from houdini to blender but it was not compatible with blender and blender could not read it
Is there any way to do that whether it is Python scripting or any way so that i can bring that pyro smulation from houdini to blender ?

Moving a pyro vdb (or any vdb for that matter) from Houdini to Blender 2.9, is fairly straightforward if your pyro sim is set up with a convert vdb and file cache sop.
Here is the end of the Houdini node tree for the pyro vdb shown below:

The convert vdb sop instructs houdini to convert your pyro into a vdb sequence(change it to vdb, as it defaults to volume,) it should look like so in the parameters--> , and the file cache will save it to disk at the output. (be sure to change cache to output to .vdb from .bgeo or you may run into problems on export)

Alternatively, (and for a more efficient way)you may  use a Pyro-Post-Process sop in place of the convert vdb sop. This will allow to do the conversion to vdb and tell houdini to save  the vdb as 16 bit float instead of 32 bit (default).

The parameters of the pyro-post-process should look like this:

Inside of Blender, add a volume object in the scene, Shift+A Volume >Import OpenVBD and select your sequence wherever it was saved to. Blender should now read the vdb sequence exported from houdini without any problems.

Nice answer! In order to save some space on the graphics card for cycles/eevee you might want to add a primitive sop after the vdb conversion and set it to 16bit or just put down a pyro post process node which allows to do both steps in one go.

@p2or indeed! Pyro-post-process is much more efficient!


text:
Blender - Python Script to batch convert all material surfaces to Principled BSDF
The Original Problem (SOLVED, thank you Gorgious) :

When I import models, they have materials with "Specular BSDF".
I'm looking to change all surfaces to "Principled BSDF".
If I did this manually, it would look like this: https://i.sstatic.net/NjqNS.png
This is what my shading tab looked like originally: https://i.sstatic.net/w4H5h.png

The script below is what I'm using, now.
It converts the materials to Principle BSDF, then sets some properties, then flips the normals. This prepares me to take imported .mqo models and export them to .glb for 3D modeling purposes.

import bpy

# Convert Materials to Principled BSDF
for mat in bpy.data.materials:
    if not mat.use_nodes:
        continue
    nodes = mat.node_tree.nodes
    specular = next((n for n in nodes if isinstance(n, bpy.types.ShaderNodeEeveeSpecular)), None)
    output = next((n for n in nodes if isinstance(n, bpy.types.ShaderNodeOutputMaterial)), None)
    if specular is None or output is None:
        continue
    principled = nodes.new("ShaderNodeBsdfPrincipled")
    principled.inputs[0].default_value = specular.inputs[0].default_value
    principled.inputs[9].default_value = specular.inputs[2].default_value
    principled.inputs[19].default_value = (0, 0, 0, 0)
    principled.inputs[21].default_value = 1 - specular.inputs[4].default_value
    principled.inputs[14].default_value = specular.inputs[6].default_value
    principled.inputs[15].default_value = specular.inputs[7].default_value

    principled.location = (specular.location[0] - 100, specular.location[1])
    mat.node_tree.links.new(principled.outputs[0], output.inputs[0])
    nodes.remove(specular)

# Set Material Properties
def remove_links(socket: bpy.types.NodeSocket, node_tree: bpy.types.NodeTree):
    for link in socket.links:
        node_tree.links.remove(link)

def fix_node(node: bpy.types.Node, node_tree: bpy.types.NodeTree):
    if node.type == 'BSDF_PRINCIPLED':
        node.inputs['Specular'].default_value = 0.5
        node.inputs['Metallic'].default_value = 0.0
        remove_links(node.inputs['Alpha'], node_tree)
        remove_links(node.inputs['Normal'], node_tree)

def fix_material(material: bpy.types.Material):
    for node in material.node_tree.nodes:
        fix_node(node, material.node_tree)

def fix_selected():
    for object in bpy.context.selected_objects:
        for material_slot in object.material_slots:
            fix_material(material_slot.material)

# Flip Normals
scn = bpy.context.scene
sel = bpy.context.selected_objects
meshes = [o for o in sel if o.type == 'MESH']

for obj in meshes:
    bpy.context.view_layer.objects.active = obj
    bpy.ops.object.editmode_toggle()
    bpy.ops.mesh.select_all(action='SELECT')
    bpy.ops.mesh.flip_normals()
    bpy.ops.object.mode_set()

if __name__ == "__main__":
    fix_selected()

Are there things linked to the specular bsdr or are there only values ? You can check it out by going in the shader editor. If there are link going out of the left of the shader node, then there are links. For context I'm asking this because it would be pretty easy to convert specular bsdf to principled but a little bit harder if there are links

does it look like this or that ?

Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking.

This will swap all Specular BSDf nodes to Principled BSDF nodes. However the specular color parameter isn't available on the Principled BSDF so you may experience loss of data there.

import bpy

for mat in bpy.data.materials:
    if not mat.use_nodes:
        continue
    nodes = mat.node_tree.nodes
    specular = next((n for n in nodes if isinstance(n, bpy.types.ShaderNodeEeveeSpecular)), None)
    output = next((n for n in nodes if isinstance(n, bpy.types.ShaderNodeOutputMaterial)), None)
    if specular is None or output is None:
        continue
    principled = nodes.new("ShaderNodeBsdfPrincipled")
    principled.inputs[0].default_value = specular.inputs[0].default_value  # Color
    principled.inputs[9].default_value = specular.inputs[2].default_value  # Roughness
    principled.inputs[19].default_value = specular.inputs[3].default_value  # Emission color
    principled.inputs[21].default_value = 1 - specular.inputs[4].default_value  # Alpha
    principled.inputs[14].default_value = specular.inputs[6].default_value  # Clearcoat
    principled.inputs[15].default_value = specular.inputs[7].default_value  # Clearcoat roughness

    principled.location = (specular.location[0] - 100, specular.location[1])
    mat.node_tree.links.new(principled.outputs[0], output.inputs[0])
    nodes.remove(specular)

Hey Gorgious, this worked! There's only one last value that I'm unsure on how to set. I would like to change the "Emission" (specifically, the "H" / "S" / "V" / "A" that it default displays)... all to zero. I'm currently looking around for the answer, but haven't been able to combine it into the script, yet. Any ideas on this?

@DerekHettinger sure replace the line principled.inputs[19].default_value = specular.inputs[3].default_value with principled.inputs[19].default_value = (0, 0, 0, 0)

Thank you, again. The OP reflects the script I'm using. Pretty much, 1 click to prepare the models for export into .GLB. You saved me a TON of time!


text:
Weird artifacts on blender workbench and evee 3D viewport (v 3.31 LTS)
anybody shared this issue? thank's

@Gorgious : I've checked the normal see 2 last images

Your polygon normals look messed up.

@Gorgious : I've updagted original post to reply to you

Check for custom split normals under the Mesh tab in the properties editor (Green triangle icon) and remove them if there are any

There is no Split normal neither weighten normale modifier. For info in Cycle it s fine... this rocket is inserted from asset library and in the source file everything is perfect... thank you for your help. Maiby my blender file is corrupted...


text:
How to draw Object selection with eyedropper layout using Python script
I wanted to draw this Object selector layout using Python Script
and Retrive the Selected Object Also Apply the Modifier to Selected Object

I have Tried this from the another question asking for same thing
but that is not working
import bpy

class Test_PT_layout_panel(bpy.types.Panel):
    bl_label = "Prop Panels"
    bl_category = "Test Panel"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "output"

    def draw(self, context):
        layout = self.layout
        string_property = PointerProperty(type=bpy.types.Object)
        col = layout.column()
        col.prop(scene, "string_property", context.scene, "objects")

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

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

if __name__ == "__main__":
    register()

Enable developer tools in user preferences.  Right click on UI element and choose view source to open the python source of the UI in the text editor.

I am Not able to See or Understand Much in Source code col.label(text="Object:")
col.prop("md, object", text="") I have seen These two Lines about this thing in source code but not understood How to add that Out of Modifier

I'd like to remind you that StackExchange is a Q&A site that values questions that show that an effort has been made to solve the issue before posting. This is explained in Search and research "How to ask a good question".

Related question https://blender.stackexchange.com/questions/30487/object-selection-box-with-eyedropper

@Robert Gutzkow Thats What I wanted thank you for Posting Link to that Question Now Let me Try it

Tested the code of the dupe, I don't have any trouble. Where your "string_property" is defined?

Ok I edited this question and now string_property = PointerProperty(type = bpy.types.Object) but still it do not create that type of object selector layout

Either use col.prop_search(scene, "string_property", context.scene, "objects")   or   col.prop(scene, "pointer_property") (note the difference, coding is about attention to detail)  Btw define your pointer property in the register method. The draw method is for drawing UI.

You forgot to "register" your property to any bpy type like the actual scene. Add bpy.types.Scene.string_property = bpy.props.PointerProperty(type=bpy.types.Object) to register() and col.prop(scene, "string_property") to your draw() method @Rakeshchoudhary

More about Add-on development here: How to create a custom UI?

sorry to be silly can anyone  answer me somewhat descriptively so i could understand

Added answer to dupe. Please take some time to evaluate the changes between script above and script there.  To reiterate, coding is attention to detail.


text:
Drawing Float Property
I needed a Help in Drawing a Property Group,
I created a Color ramp in Line 78 and needed Control for the Slider and for that I assigned this to the position_control in line number 85.
and I wanted to draw the Slider of that position Control and I tried following this to create this
I just Made the Class for Float Value but perhaps I am facing the Issue in Registering at the end as I don't know how to do this as this error is shown -

Traceback (most recent call last):   File "\TEST_MATERIAL.py", line
158, in  AttributeError: ramp_pos Error: Python script failed,
check the message in the system console

Can anyone help me with this problem?
bl_info = {
"name": "Add Test Material",
"author": "Rakesh Choudhary",
"version": (1, 0),
"blender": (2, 83, 0),
"location": "View3D > Sidebar > Test Material Node",
"description": "Click on the 'Test Material' button to add a material to your object.",
"warning": "",
"wiki_url": "",
"category": "3D View"
}

import bpy
from bpy.types import (
    Operator,
    Panel,
    PropertyGroup,
)
from bpy.props import (
    FloatProperty,
    PointerProperty,
)

class TEST_MATERIAL_OT_add_material(Operator):
    bl_idname = "test_material.add_material"
    bl_label = "Add Test Material"
    bl_description = "This button will add a material to your object"

    def execute(self, context):
        self.create_material()
        return {'FINISHED'}

    def create_material(self):
        test_shader_mat = bpy.data.materials.new("TestMat")
        mesh = bpy.context.object.data
        mesh.materials.clear()
        mesh.materials.append(test_shader_mat)
        bpy.context.object.active_material.use_nodes = True

        for mat in bpy.data.materials:
            if "TestMat" in mat.name:
                nodes = mat.node_tree.nodes
                for node in nodes:
                    if node.type != 'OUTPUT_MATERIAL':  # skip the material output node as we'll need it later
                        nodes.remove(node)

        # Creating Node Group Test_Material
        group = bpy.data.node_groups.new(type="ShaderNodeTree", name="Test_Material")

        # Creating Group Input
        group.inputs.new("NodeSocketColor", "Diffuse Color")
        group.inputs.new("NodeSocketColor", "Glossy Color")
        group.inputs.new("NodeSocketFloat", "Glossyness")
        input_node = group.nodes.new("NodeGroupInput")
        input_node.location = (-800, 0)

        # Creating Group Output Node
        group.outputs.new("NodeSocketShader", "Diffuse Color")
        group.outputs.new("NodeSocketShader", "Glossy Color")
        group.outputs.new("NodeSocketShader", "Mix Output")

        output_node = group.nodes.new("NodeGroupOutput")
        output_node.location = (1500, 0)

        # Creating Diffuse Node
        diffuse_node = group.nodes.new(type='ShaderNodeBsdfDiffuse')
        diffuse_node.location = (150, 100)

        # Creating Glossy Node
        glossy_node = group.nodes.new(type='ShaderNodeBsdfGlossy')
        glossy_node.location = (300, 250)

        # Creating Mix Shader Node
        mix_shader_node = group.nodes.new(type='ShaderNodeMixShader')
        mix_shader_node.location = (450, 100)

        #Creating Color Ramp
        col_ramp = group.nodes.new(type="ShaderNodeValToRGB")
        col_ramp.location = (400, -300)
        col_ramp.color_ramp.elements.remove(col_ramp.color_ramp.elements[0])

        col_ramp.color_ramp.elements.new(0.750)
        col_ramp.color_ramp.elements[0].color = (0,0,0,1)

        position_control = col_ramp.color_ramp.elements[0].position

        col_ramp.color_ramp.elements[1].position = (1.0)
        col_ramp.color_ramp.elements[1].color = (1, 1, 1, 1)

        # Creating Links Between Nodes
        group.links.new(diffuse_node.outputs["BSDF"], mix_shader_node.inputs[1])
        group.links.new(glossy_node.outputs["BSDF"], mix_shader_node.inputs[2])
        group.links.new(input_node.outputs["Diffuse Color"], diffuse_node.inputs[0])
        group.links.new(input_node.outputs["Glossy Color"], glossy_node.inputs[0])
        group.links.new(input_node.outputs["Glossyness"], glossy_node.inputs[1])
        group.links.new(output_node.inputs["Diffuse Color"], diffuse_node.outputs[0])
        group.links.new(output_node.inputs["Glossy Color"], glossy_node.outputs[0])
        group.links.new(output_node.inputs["Mix Output"], mix_shader_node.outputs[0])
        group.links.new(col_ramp.outputs["Color"], mix_shader_node.inputs[0])

        # Putting Node Group to the node editor
        tree = bpy.context.object.active_material.node_tree
        group_node = tree.nodes.new("ShaderNodeGroup")
        group_node.node_tree = group
        group_node.location = (-40, 300)
        group_node.use_custom_color = True
        group_node.color = (1, 0.341, 0.034)
        group_node.width = 250

        shader_node_output_material_node = tree.nodes["Material Output"]
        links = tree.links
        links.new(group_node.outputs[0], shader_node_output_material_node.inputs[0])

class Col_ramp_Property(PropertyGroup):
   ramp_pos : FloatProperty(
       name = "Position",
       description = "A float property",
       default = 0.75,
       min = 0.01,
       max = 1.0
    )

class TEST_MATERIAL_PT_layout_panel(Panel):
    bl_label = "Test Material Node"
    bl_category = "Test Material"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"

    def draw(self, context):
        layout = self.layout
        C = bpy.context
        position_control = C.active_object.active_material.node_tree.nodes.col_ramp.color_ramp.elements[0].position
        layout.operator("test_material.add_material", icon='IMPORT')
        row = layout.row()
        row.prop(position_control, "ramp_pos")

classes = (TEST_MATERIAL_OT_add_material, Col_ramp_Property, TEST_MATERIAL_PT_layout_panel)

def register():
    for cls in classes:
        bpy.utils.register_class(cls)
    bpy.types.Scene.ramp_pos = PointerProperty(type=Col_ramp_Property)

def unregister():
    for cls in classes:
        bpy.utils.unregister_class(cls)
    del bpy.types.Scene.ramp_pos

if __name__ == "__main__":
    register()

I set C = bpy.context
position_control = C.active_object.active_material.node_tree.nodes.col_ramp.color_ramp.elements[0].position

and still there is the same problem, I think the main problem is I couldn't find the correct path to(how to access) the colorramp's element's position

You're missing the import for the PointerProperty. Also the code is not properly indented, the assignment and deletion aren't part of the register() and unregister() function.

@RobertGützkow Thanks for answering, I edited the Question and Imported the PointerProperty and also Indented the code but still giving that error - ValueError: bpy_struct "Col_ramp_Property" registration error: ramp_pos could not register

You're assigning strings to values that should be floats (default, min, max).

Here https://blender.stackexchange.com/questions/57306/how-to-create-a-custom-ui this thing(default, min, max) are done this way only and now blender is showing this error - 'RNA_Types' object has no attribute 'ramp_pos' Error: Python script failed, check the message in the system console

Read Robert's comment carefully. One obvious issue: "Col_ramp_Property" is a string right? ...and you actually have to assign a class type... Again, recommend to take a basic python course.

How is it a String? Under the Class, I have defined - ramp_pos : FloatProperty Can you Please tell me how to assign class type or how will this problem be solved as I wanted to take the position of element of color ramp and draw that in panel

Try to understand what you're doing. You are assigning a string to type: type="Col_ramp_Property". Assign the actual class type: type=Col_ramp_Property. Do you get the difference now?

@brockmann Thanks for your answer and after solving this a new error is there and this time it is - AttributeError: ramp_pos

I guess complete error message is: position_control has no attribute ramp_pos. Question is: Where position_control variable comes from? Not declared in the panel class...

Error is Just that much only AttributeError: ramp_pos But I agree that the problem may be in the position_control variable actually I have declared that above position_control = col_ramp.color_ramp.elements[0].position But I don't know how to declare it in Panel as I don't know the path to the color ramp element.

Have a look how this is done over here in OBJECT_PT_CustomPanel class.

@brockmann thanks again for the reply I have already read that before but still, I read that again and I found my Mistake and Now I have added that to the Panel but actually now the Problem is I couldn't access the color ramp. Could you tell me please, how do I access them as the material(the color ramp is defined in it ). as the material will only be created when the operator will be called from the panel. so what is the right way to do this?

Please don't change your question each time - Imagine someone is already writing an answer (at the moment) and you are changing the question that drastically, it's a waste of time and not fair. This also means that if you can draw the property, we are done here IMHO. I suggest ask a new question on how to do... @Rakeshchoudhary

@brockmann Ok, thank you very much I am going to ask a new question for this problem.

... and you don't "found the mistake" -> this: C = bpy.context in combination with position_control = C.active_object... within an operator method is no good. First of all, you already have context, use it! Next, If you had read the contents of OBJECT_PT_CustomPanel in the answer I suggested you should now that you need a reference to the PointerProperty (Scene.ramp_pos) so it is mytool = context.scene.ramp_pos and then row.prop(mytool, "ramp_pos"). confusing to read due to your naming.

@brockmaan  thanks for answering I tried this but it is still giving an error. I think the problem I am facing is in accessing the color ramp's element's position. So I have asked a new question with some clarity- https://blender.stackexchange.com/questions/183147/accessing-nodes-in-a-node-group-to-draw-property-in-panel


text:
How to create a new material and set it as active material using python script
How can I create a new material and set it active material on the active object using python script.

You could do it like this:
obj = bpy.context.object  # Select the active object.
mat = bpy.data.materials.new(name='Material')  # Create a material.
# Settings for the material go here.
obj.data.materials.append(mat)  # Assign the new material.

bpy.ops.material.new(name='zz') now gives me 'keyword "name" unrecognized' in blender 2.9