text:
Superimposing architectural models onto street photographs
I wanted to use 3D MAX to create architectural renders, but I have a Mac, so I am looking into Blender as an alternative solution.
The models look amazing and the rendering is fab, but I am struggling to find a tutorial to help me superimpose my model onto the photograph of a street or equivalent. I have to supply images of the model in situ, so I am really hoping there is a way. Please can someone help me?
Thank you

https://blender.stackexchange.com/questions/154792/how-to-render-a-background-image-in-2-8 https://blender.stackexchange.com/questions/52204/is-there-a-way-to-know-camera-information-from-an-image-visually-without-exif/52207#52207

If you want to place your models so they look like they are part of a photograph, you should be looking for VFX (video effects) tutorials.
CG Geek has a few on YouTube, where he adds objects to video footage, but the same techniques apply for still photographs.
Blender Guru has some too.  Try searching for "How to render onto a photo background" on his website.


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A part of my model disappears when i enter edit mode
Pretty much the title. Here's some screenshots:
Object mode:

Edit mode:

Luckily I'm done and it still exports like normal. What caused this? Is there a fix?

This worked! Thanks a lot. I thought I tried that, but it must have been in object mode. Thanks again!

source: Stack Exchange

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

sort: votes


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Is it possible to get vertex locations (world) from a vertex group?

How can I get the vertices location connected to animated bones?
E.g. the vertices of vertexgroup "foot.L" at keyframe 2?

Copy Location Constraint.
From https://blender.stackexchange.com/a/139758/15543

Can leverage the existing behaviour of the copy location constraint, targeted to a mesh, subtargeted to a vertex group.
Test script, run in object mode with mesh object selected. Will add an empty for each vertex group at the mean location (as determined by constraint) of each vertex group.
import bpy

context = bpy.context

ob = context.object
me = ob.data

for name in ob.vertex_groups.keys():
    bpy.ops.object.empty_add(location=(0, 0, 0))
    mt = context.object
    mt.name = f"{ob.name}_{name}"
    cl = mt.constraints.new('COPY_LOCATION')
    cl.target = ob
    cl.subtarget = name

Thanks, this gives me the center of the vertex group. Is it possible
  to get the location of all vertices (not only the center)?

Or using another slightly updated example from https://blender.stackexchange.com/a/139758/15543
this one adds an empty parented to each vertex in the vertex group.
For vertex group named "Group" containing vertex index 3, there will be an empty object mt named "Group_3" parented to vertex 3.  At any frame the global location of vertex 3 will be mt.matrix_world.translation.
import bpy
from collections import defaultdict
context = bpy.context

vgs = defaultdict(list)
ob = context.object
me = ob.data
for v in me.vertices:
    for g in v.groups:
        vgs[ob.vertex_groups[g.group].name].append(v.index)

for name, vg in vgs.items():
    for i in vg:
        bpy.ops.object.empty_add(location=(0, 0, 0))

        mt = context.object
        mt.parent = ob
        # mt.name = "%s_%d" % (name, i) # for python < 3.6
        mt.name = f"{name}_{i}"
        mt.parent_type = 'VERTEX'
        mt.parent_vertices = (i,) * 3

Note would be a good idea here to jam empties into new linked collection, so they can be removed / hidden easily
Another way is to use one of the solutions outlined here
How do I get a mesh data-block with modifiers and shape keys applied in Blender 2.8?
for a modified mesh. However if you have a subsurf, for example,  will have a lot of extra generated vertices.

Thanks, this gives me the center of the vertex group.
Is it possible to get the location of all vertices (not only the center)?

I extended your first answer, this does work:

ob = bpy.data.objects['Person:Body']
me = ob.data

for name in ob.vertex_groups.keys():
    bpy.ops.object.empty_add(location=(0, 0, 0))
    mt = context.object
    mt.name = f"empty_{ob.name}_{name}"
    cl = mt.constraints.new('COPY_LOCATION')
    cl.target = ob
    cl.subtarget = name
    mt.matrix_world = mt.matrix_world.copy()
    mt.constraints.clear()

So, I am able to get the location of the vertex group per frame.
However, I can not get the location of the vertices. I tried out your second suggestion.
Obviously, they are not at the same place as the animated Person is located.

Image shows the location of one vertice of the thumb (created empty), which is in the left corner instead of on the person.

actually I need the position of the linked parent vertex, but can't figure out how. So the location at the end of the black line

I'm so sorry, didn't have time to deeper look into this. Thanks so much for your support @batFINGER. I will check this weekend :)

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


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Selected meshes vanish when in object mode
So, I’m a total noob at Blender, just started learning it last week by using the Blender Guru’s Donut tutorial. During the process I found a problem with my Solidify Modifiers that I managed to fix (a problem with the normals I believe) but in the process I might have broken something. I’ll explain what happens with a New file (I tried reinstalling Blender 2.81, reseting settings and such and it didn’t work) cause it now happens everytime.
When I open a new file I find this:

Aparently nothing, right? But as you may notice, there is in fact a default cube.
When I change from Object to Edit Mode, I can see that it is selected and it looks normal.
And when I deselect it and go back to Object mode it’s back to normal. This also happens with individual selected faces so I guess the problem is with my selections? Also, this only happens in Solid Mode cause in Render Mode it looks as it’s suppose to be.
Does someone knows what may be causing this? I can’t find anything on the subject (Sorry if there is, I just couldn’t find it).
Thanks in advance ^^

Could you save the default file, and upload it to https://blend-exchange.giantcowfilms.com/? Then just paste the given code

Sorry it took me so long I didn't have access to my computer XD
I can't upload the file for some reason T_T
Does uploading it to my dropbox works?

Sure, as long as its public. Would you mind also posting your system specs?

I'll send my Drive instead XD
https://drive.google.com/open?id=1mTeDNy9zCKAOb0u9NyJXHCS2L02gsXn0
Windows 10 Pro 64bits
Intel(R) Core(TM) i7-3770K @ 3.50GHz, 3501 Mhz. 4 Core(s), 8 Processor(s)
RAM 4GB

Hm, nope the cube shows up on my screen, not quite sure what the cause is. Can you add new objects like normal?

Yeah, I can add new objects normally. This bug doesn't stop me from doing things but it's really inconvenient having to unselect everything to see it in Object Mode :/
Maybe if I install an older version and then update it to the new one? I'll try that

Instead of going through that hassle,, delete the default cube then go to File > Default File > Save as Default. That will remove the buggy cube from your startup file. You'll only have to do that once so it's not too bad of a workaround

It didn't help cause every mesh I add and it's selected have that bug. And aparently the problem is in version 2.81 cause 2.80 is fine

Most definitely a glitch, because the only other instance I know of something like  this happening is when a cube I added in POV-ray rendering disappeared in edit mode because a certain script wasn't installed. Try re-opening Blender, and if that doesn't work, then you may have to uninstall Blender then re-install it.

Yeah, I tried both already and It didn't work T_T

This is not usual. It is not Blender then, that has the glitch. Check your graphics card.

My computer doesn't have a GPU :/
But it was working fine when I first installed it


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Problem with vertex painting
I'm trying to do a low-poly tutorial and I want to use vertex painting to paint the island but the brush doesn't paint... I'm a begginer, please someone can help me?

https://youtu.be/AnRQhH3fEDY
You might want to watch this, I don't think that vertex paint is actually for changing the colors of your mesh.

You're in a rendered preview, and the material you're showing is not referencing your vertex color layer at all.  Consider creating a "vertex color" node, giving it the name of your vertex color layer (like "Col") and plugging it into the Base Color input on your material's Principled BSDF.


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why won't my character with the rig move?
I made a basic TABS model for my first model and wanted to rig it. I followed many tutorials but no matter what I do the character won't move with the rig. Where only 2 instances where it did work (kinda)

if I turn on bone envelopes which isn't really a solution
when I scale up the character and rig and then add automatic weights which will for some reason lead to the character also shrinking

I tried redoing the rig, making a rig using rigify etc.nothing seemed to work
here is the blender file
https://drive.google.com/file/d/1U2zm3tueuc1XkO41nGONfsaoOorvZrax/view?usp=sharing

Apply the scale of both the two objects, parent With Automatic Weight, it works:

I don't quite understand what you mean
when you say two objects do you mean the rig and the model?

sorry but I still don't understand
when i try to parent the rig, "automatic weights doesn't pop up

How exactly do I do that
sorry for being a bother but I'm pretty new to blender

Select your character, press Ctrl A and apply the scale, do the same thing for the armature. Now select the character, shift select the armature, press Ctrl P and choose the With Automatic Weight option

Thank you so much!


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Why does my rig extend when I export
Whenever I export my rig all the end bones duplicate and add "_end". the rig works fine but it's only when I export.
Images

Here is the blender file

This is a limitation of the export format you are using, and doesn’t really have to do with blender. Ignore the end bones, and attempt posing the model.

yeah but this is a problem when I import it to unity where the duplicated bones disappear leaving the character without arms, head, or feet


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Setting presets with operator menu (precise)
Not sure if this question is blender related or pure python.
Please let me know if this is pure python. I will delete this question here and ask it on PythonStack.
I am using the presets function in the OOTB operator dialog.
What I notice in the preset files is that it writes back my presets but adds extra numbers to it. I guess this happens because the property is a float property.
This is the entry that is saved.
op.test = 0.010287000797688961

This is how it supposed to be
op.test = 0.010287000000000000 (10.287 mm)

Is there a way to make sure the presets will be precise?
Since it is being written using the preset function I don't know if a simple python code can fix this.

Similar to another recent question, float supports only 8 digits of precision. I suggest using a StringProperty and storing the value as a string, then parsing it at runtime when you need it with float(value)

@Gorgious sorry for pedantism, float32 supports 24 binary digits of precision, and for the most part it can be represented in 8 decimal digits, but to guarantee the number is fully recovered when converted back to float32 you need 9 decimal digits. Also note the number is truncated to 8 significant digits (results in 5 s.d. due to 3 zeroes), rather than rounded, which would produce 0.010287001. Probably an implementation quirk, which limits the precision for UX purposes...

It's also worth to note that usually trying to save 0.010287000797688961 as float will result with 0.010287000797688961029052734375 being stored (00111100001010001000101011001111 in memory), while 0.010287 is a different float 0.01028699986636638641357421875 (00111100001010001000101011001110 in memory)


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angle of segment opposite
Using a script to make a circle segment I run into this "Issue"
The default value of the angle is 120.
When running the script it draws vertices starting at the left side.
See screenshot

As you can see the angle is 120 degrees (this should be zero (0)
See next screenshot

The degrees is now 0 and the segment is drawn.
Off course this should be the opposite. (0 is not drawn and 120 if drawn)
What do I need to change in the angle_end var to flip the angle?
Default value is 120. When running the script it should draw the segment and not 1 vertice.
Code snippet attached below
h = self.height
diam1 = abs(self.diam)
r = diam1/2
selfangle = abs(self.angle)

    # Circle partially above x-axis
    angle_start = math.pi - math.asin(h/r) ##math.pi - math.asin(h/r)
    **angle_end = (math.pi - angle_start + math.radians(self.angle))**

for i in range(self.segments+1):
    factor = i / self.segments
    angle = angle_start*(1 - factor) + angle_end*factor
    verts.append((math.cos(angle)*r, math.sin(angle)*r - h, 0.0))

do you have full code?

I will add the code later and edit the post


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Mountain object resizes and moves in animation
I have created a mountainous snow scene for an animation I'm doing but I must have had auto-key on when I resized some of the landscape because when I run the animation you can see the mountain moving and re-sizing in the camera view but in the viewport the mountains don't move at all! When I render the animation the mountains are moving and I don't want them to. There are no key frames on the timeline for the mountains so I don't know what to do to stop them moving. Any suggestions please?

Might this apply here? https://blender.stackexchange.com/questions/280437/object-still-animates-despite-not-having-any-keyframes-in-dope-sheet-or-timeline.

Hi John, many thanks for your suggestion. I have checked the NLA channels and there was indeed a node for the landscape which I deleted from that channel so it is clear of actions. However, even if I delete that particular mountain object it still somehow resizes during animation. I tried going back a few steps and creating a new landscape mountain but, again, it moves and resizes during animation in the camera view but not in the viewport window. I'm stumped & stuck, I'm afraid!

I'm afraid that I'm not very familiar with animation problems so someone else will have to offer suggestions there! Can you upload the Blend file or at least edit your question and add a link to it? That way it will be resubmitted and someone else may be able to help?


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Texture resolution for big objects
I apologize at once for a possibly stupid question. But I have this question. Suppose we have a model of a building for the game, let's say the texture of the building at the player's eye level will be in high resolution, but then how to make sure that the top of the building has a texture with low resolution, while not showing a sharp transition between the two textures. I assume I have to divide the model into several parts and the higher the part from the player, the resolution of the textures bklt less, as well as the level of detail. Am I right? And how to choose the right place where there will be this transition texture?

hello and welcome, this question doesn't really seem to be about blender lol

Ussually this is handled by game engine automatically. In Blender it was previously handled by MIP map feature to speedup viewport, but again it was automatically generated by app.
So probably let us know - What is your specific use case ... What app is going to be used for your textures?

Just for a curiosity ...
For simple objects like skyscrapers you can create a classic material with even UVmap ...

... than create another UVmap squeezed by Proportional Editing enabled under UV editor ...

Under Shader add another free Image Texture (for baking keep selected) with squeezed UVmap assigned.

Bake it and use as source texture for material ...

... like that upper floors take a fragment of pixels than lower floor close to viewer in baked texture, but from street level it will looks fine.

Note: To bake it properly ...

Image Texture node you are baking at, has to be selected (active) in shader node tree
to bake from original UVmap to sqeezed UVmap keep in mind - original UVmap has to have a render icon ON and squeezed UVmap has to be selected in the list - grayed row (it was painful discovery for me :) ) ...

Thanks for your reply. That is good information


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How can I create a custom property set for the objects using Python?
I have to code a custom property and quantity set for objects in my Blender scene using Python. I'm a rookie in this kind of stuff, is there someone who can help me? Thank you!
I've tried to follow also this Adding Other types of Custom Properties but it doesn't work for my aims

Hello, so what is your goal exactly ? Could you elaborate on that ? Otherwise we can't help you

Hello @Gorgious and thank you for your answer. I want to get a custom pset for each object in the scene with object type, quantity, etc. I don't if I explained myself well, but I hope yes. If you need clarification let me know. Thank you in advance!

I assume you're using the BlenderBIM addon ? You might want to head over to https://community.osarch.org/ where there will be more people suited to answer your question

Ok, thank you for information


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Keep last keyframes and delete the others
I have a script that run a rigid body simulation and I want to keep only the last keyframes and delete the previous ones. Is there a way to do this? Thank you for the availability.

i don't think, that you only want to delete only the keyframes, tbh. Maybe you wanna give us some more informations, what you are going to do? Do you want a still image of the last frame? do you want to continue/start the rigid body simulation from the last frame? or do you want to manually animate the objects after the last keyframe? Because "only" deleting keyframes shouldn't be a problem at all...

Sorry for the fewer pieces of information, what I'm trying to do is keep the final model that comes out from the simulation and then make on it other kinds of operations. For example, I've just tried to assign Ifc class after the simulation but I make that the model comes back on the first simulation keyframe. So I had idea to keep the last keyframe and delete the others. I don't if I made the idea of what I'm trying to do, I hope so. Thanks for the feedback

just go to your last keyframe, then object -> rigid body -> apply transform. Then you can delete all keyframes and rigid body (if u want to)


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Add the cubes on specific keyframe
I have a grid 8x8 of cubes and I would that each cube fall down one by one and I imagine that each cube had to assign on a specific keyframe but I don't know how to do in python bpy. Below there is the code that I work with, maybe someone has an idea.
Thank you in advance
import bpy
import numpy as np

mass = 1000
f = 0.8
d = 0.999
start_frame = 0
delta = 14400

Dn = 1
nx = 8
ax = 1.2
ny = 8
by = 1.2

x0 = -4.2
y0 = -4.2
z0 = 3.

cube_mesh = bpy.ops.mesh.primitive_cube_add()
bpy.context.active_object.dimensions = (1,1,1)

bpy.ops.object.select_all(action='DESELECT')
cube = bpy.data.objects['Cubo']
cube.select_set(True)
bpy.context.view_layer.objects.active = cube

bpy.ops.rigidbody.object_add()

rigid_body = cube.rigid_body
rigid_body.type = 'ACTIVE'
rigid_body.mass = mass
rigid_body.friction = f
rigid_body.linear_damping = d

xx = np.arange(x0, x0+ax*Dn*nx, ax*Dn)
yy = np.arange(y0, y0+by*Dn*ny, by*Dn)
data = []

for x in xx:
    for y in yy:
        data.append([x,y,z0,np.random.randint(0,120)])

print('data',data)
lines = len(data)

for line in range(lines):
    pos = data[line][:3]
    delay = data[line][3]
    print('pos', pos)
    bpy.ops.object.duplicate()
    obj = bpy.context.active_object
    obj.location = pos

    obj.rigid_body.enabled = True
    obj.hide_viewport = False
    obj.rigid_body.linear_damping = d

    obj.keyframe_insert(data_path='hide_viewport', frame=start_frame)
    obj.keyframe_insert(data_path='rigid_body.enabled', frame=start_frame)
    obj.keyframe_insert(data_path='rigid_body.linear_damping', frame=start_frame)

    obj.rigid_body.enabled = False
    obj.hide_viewport = False

    obj.keyframe_insert(data_path='hide_viewport', frame=start_frame + delay)
    obj.keyframe_insert(data_path="rigid_body.enabled",frame=start_frame + delay)

    obj.rigid_body.enabled = True
    obj.keyframe_insert(data_path="hide_viewport",frame=start_frame + delay + 1)
    obj.keyframe_insert(data_path="rigid_body.enabled",frame=start_frame + delay + 1)

obj.select_set(False)

cube.select_set(True)
bpy.ops.object.delete()

Why isn’t this code working? What happens?

Sorry, I have set italian language on blender so to make the code working you have to switch 'Cubo' with 'Cube'

What I mean is that you didn’t have any output of the code. What’s going wrong? I don’t want to just try to run it myself, because I might not have things set up quite the same way as you, and just synchronizing our set ups will probably take as long if not longer than solving the problem.

If you run it from blender the output is a grid of cubes 8x8 while if you run it from another debugging program you will not get any graphical output. Thak you!

After a brief review, it sounds like the code is working properly, but you don’t know how to pull a unique value to set the keyframes at for each cube in the loop, so they end up falling at the same time. Is that correct? What should define when the cubes fall? Is it just random?

Yes, it does. Now the cubes fall down almost at the same time and the only two parameters that define theyr fall are the "start_keyframe" and the "delay", I think so. The outcome that I expect at the end is a blender simulation where the cubes fall down one by one.

Would it be easier to share your file (or a representative sample) on https://blend-exchange.com/

When should the second cube fall? After the first has landed somewhere, or after some other specified delay?

I think the second cube falling and so on it should be defined by a specific delay. For me it is the better solution. Thank you!


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Jagged Edges and Antialiasing In Viewport With Background Images
I am on the latest LTR build (2.83.1) and have noticed that any geometry that's drawn above a background image doesn't anti-alias properly. See image for example:

Does anyone know a fix for this? Is this happening to other people as well?

Change the Depth of the reference images under Object Data Properties to Back


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Console Error when Starting Blender: SetChannelMap - Is this Normal? What does this mean?
Here's an image of my console window that pops up right before Blender opens:

Blender continues to run normally after, but the error still bugs me. And I didn't get the same error on my laptop.
After some google-fu, there was 1-2 posts about it from other users but nobody could really elaborate on what it means or why it's there. An unrelated result pointed to some kind of audio issue. Apparantly AL lib is OpenAL (Open Audio Library).
Full text of the error: AL lib: (EE) SetChannelMap: Failed to match front-center channel (2) in channel map
Do any of you get this as well? Is this normal behavior?

I've seen some stuff about this too - one discussion regarded something about a conflict/interaction with Windows audio handlers. Other users have reported that this problem was caused by old leftover files from a graphics (drawing) tablet in the system32 folder. Removing these "bad" files fixed the problem for these users. As you said, it's difficult to find much else about it.

Definitely don't have a tablet installed. I have a pair of USB headphones connected to my computer, I wonder if that's the culprit.

Your guess is as good as mine... I think the best advice I saw in that regard was "try changing windows audio settings". Not much to go on, I know, but "audio-related" is the one relatively steady theme I've come across. I guess all you can do is tinker with it.

For sure, thanks for trying to help and the additional information.


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Why is my input slider not showing the actual slider in a node group?
See this image:

I would like to have a slider for the "Less/More" value. Its range is from -1 to 1. The value itself updates, but Blender doesn't want to draw the actual blue slider.
What's the issue here?
Thanks in advance!

please [edit] your question and add an image of the contents of the node group.

I figured it out. You have to create the input from a slider value in the first place. Here's an example gif:

You can't go back and change it after the fact.

Blender simply does not draw any slider for the input values of node group
But you can have a minimum value and maximum value of any value easily set up by the pressing N in node editor
It will not be drawn as slider but it will not go less than minimum value and more than maximum value
If you want to have a slider,you may need to use any additional add-on
I don't know about any such add-on till now

Check my answer below, you can do it.

Sorry but this will not work for him because he needs the minimum and maximum value of -1 and 1... This sider just goes from 0 to 1

He can use map range node to make it work...

There is no need for a map range node, it works fine as I outlined in my answer. The slider works from -1 to +1.

Hello, this answer and your comments are not true. You can both use a slider in a node group by first linking the input to a slider field (fe the factor of a mix rgb node) and then remap it to your desired values in the node group properties in the N panel


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Understanding Blender's Invert Node and Varying Bit Depth Images
So, I am trying to wrap my head around exactly what the invert node is doing in the shader editor.
I realize that this sounds like the most simplistic question in the universe, but please bear with me. Coming from a graphic design background, I can somewhat picture what an inverted image will look like in my mind's eye. The parts that are white flip to black, and the parts that are black flip to white.
But I'm not so sure what happens when 16bit and 32bit images are inverted.
In blender, it looks like it's not really completely inverting the image being fed to it. Here are a couple images as an example (I'm using Node Wrangler here to preview):
Original Image

Inverted Image

Ok. Now, I'm not a rocket scientist. But I'm pretty sure the inverse of that image is not a purely gray/white output. My suspicion is that since the image is 32bit I'm not seeing the full dynamic range of values that exist, and the inverse shown in Blender is correct despite looking incorrect.
Fair enough.
To dig a little deeper, I took the image into Photoshop and performed an invert there.
Original Image In Photoshop:

Inverted Image In Photoshop

The results here are interesting. First, I had to convert to 16bit as Photoshop wouldn't even allow me to invert a 32bit image. But after the invert, you can see a lot more detail than what Blender shows using its invert node.
Is this because of the bit depth discrepancy (32bit / 16bit), or is Photoshop actually doing something differently under the hood? I have no freakin' clue.
To cap it all off, I did an invert using the same image, bur first converted to 8bit.
Original 8bit

Inverted 8bit

This final process looks a lot more like what I would expect from an invert operation. I realize that the bit depth is much lower, but it's at least easier to visualize the data. I can make out the distinct smooth and sharp parts of the texture, high and low frequencies, and the overall "contrast".
What I'm getting at is that being able to visualize your texture is very important when you are making creative decisions in the shader editor. If I invert a 32bit texture, all the information might be there, but I have no idea what that information looks like - I am just presented with flat gray or white.
So, In conclusion, can someone set me straight? Is there a specific way of working with high bit depth data that is more intuitive?
Thanks so much for any help, and for reading through all this garbage :)

As far I know, (and same as what the docs say) invert simply creates a negative (opposite) image.

Of course, that's what you would expect. But does this look like the opposite of this?

You can also use a color ramp after invert to get more detail for maps that don't have much, not every image is going to have the same details. Blender is not photoshop and does deal with imagery differently.

@Timaroberts I get that they are different applications. I'm not expecting Blender to be Photoshop. I'm always trying to learn how to use Blender more effectively. In that aim, understanding what is happening under the hood is always a good thing. And yes, I often use a color ramp after inverting to bring detail back. But it makes me wonder if crushing the values like that is actually the best choice.

This is due to color management (see in the render properties) and more globally to the shader and ways lights are used in the rendering.

@lemon Can you elaborate a bit more?

@Jay, have a look here https://docs.blender.org/manual/en/latest/render/color_management.html and play with the "view transform" option

@lemon Just tried this and it makes no difference. The invert node shows all white.

@Jay, nope, it depends on lights, roughness, specualirity glossyness and colormanagement: https://i.sstatic.net/asZM6.jpg


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Keyframes don't show unless 'show only selected' isn't checked
I'm having problems getting keyframes to show without showing all, which is a mess to wade through. Any pointers?
The attached file (if I can figure out how to use Blender-exchange) contains a simple plane with a material with a mix transparency. It mixes with a transparent shader, to give a disappearing effect to the plane.
In the animation window, selecting the plane doesn't show the keyframes that exist unless I show all. In a big project, this is a chore. What am I missing?
Thanks!
(2.93.5)

If you only want to show the keyframes for the Mix Shader you need to enable the Only Show Selected option, then open the Shader Editor and select the Mix Shader node.

Thank you! I had another project that I was showing the keyframes for, and didn't realize that was why!


text:
How to eliminate UV lines in render
How can I eliminate the UV lines that show up as light reflection artifacts in my renders?  What am I doing wrong?
I have uploaded a zip file containing a minimal project (about 12 MB) that gives my output at https://www.randommonkeyworks.com/files/testRender.zip.

no strange artifacts on render of your scene for me... both in Cycles and Eevee. Which are you using? Which Blender version? GPU or CPU rendering?

2.82a. Cycles, Eevee, GPU, CPU, it doesn't make any difference. If you look closely at the render, you will see striations at the UV lines. Sorry I did not set the render up to present the effect, but if you go into 3d view and choose rendered mode, moving around the model will show the effect. Once you find an angle, if you lock the camera to it and then render, the effect will be obvious.  I have figured the problem out, so I will answer it below.

You're talking about UV lines in your subject,showing some weird artifacts that don't appear in the provided blend file (see here:https://i.sstatic.net/QnPLf.jpg)... and you're talking about baking parameters... Could you please clarify everything in your description and solution found because this is really not clear and that will help others a lot! Thanks

showing some weird artifacts that don't appear in the provided blend file << YOU APPEAR to have smooth-shaded the object (right-click on it and 'Shade smooth' option), and not to have re-linked the normals to the material. If those aren't done the artifacts I outlined in the post picture appear. If you have a place to post the zip file that accepts 12 MB, feel free to put do so and put a link to it. Otherwise I am going to remove it from my server in a while.

if you just attach a blend file without the clear instructions how to reproduce the issue, it will be difficult for anyone to help without spending or wasting a lot of time. Please edit your post description and add the details that will help the next viewer who faces the issue. Also, in order to attach a blend file to stackexchange questions, please use this: https://blender.meta.stackexchange.com/questions/630/announcing-blend-exchange-a-new-solution-to-blend-hosting. This is a community Q&A site that's supposed to help everyone, not a one way technical support hotline.

...not a one way technical support hotline. As I posted an answer, obviously I did not treat this as such, so there was no need for a statement like that. Anybody who faces the same problem will now be able to google it and solve it with the existing text, since the problem is exactly what the title says. Thanks for trying to help, and have a great day!

You're right, may be a bit arsh, I apologize for that phrase. I stand by the rest. Also, thanks for the answer.

The answer is simple. When creating the normal map, make certain your objects are smooth shaded. I don't remember any of the tutorials I saw stressing the importance of this fact, but if they aren't smooth shaded Blender will not automatically interpolate to smooth, and your normals will have abrupt changes at the grid lines.


text:
Splitting bezier/nurb paths into multiple strands?
I've been trying to add hair to my stylized character sculpt using the curve technique that many youtube tutorials teach, but I find myself quite stumped on something; If I want to have one strand of hair split into 2 smaller ends of hair, how would I do that?
I've kinda done this before by just duplicating the strand and moving the ends of the path slightly to achieve a similar effect, but this isn't ideal since it both doubles the polycount and doesn't really connect to the original strand organically (They're noclipping through each other)

This is a scuffed diagram of what I'd like to do. Just be able to extrude at a node and it have it properly create a new strand instead of the mess it actually creates in blender

Here's another diagram, from the artwork (Artist) I'm basing the hair from. You can see how one 'thick' strand splits into 2 smaller curved strands
I imagine it might be possible by duplicating the strands, making them into a mesh, then sculpting them so that the seam and overlap are unnoticeable, however, this is pretty time consuming and forces me to retopolgize the hair; I'd be grateful to hear any techniques for doing this as easily as possible!
(There is a similar question involving cables, but I do believe it is a different enough issue to warrant a separate question. Sorry if it isn't)


text:
Is there a way to preserve the thickness of a (poly) curve?
I have a poly curve which makes a square, so the thickness of the curve remains constant. When I move one of the handles downwards, elongating the shape, the thickness of the curve changes:

Is there a way to maintain the thickness of the curve automatically? I've found I can subdivide the sides and then move the resulting points very close to but not at the downmost vertex to achieve what I want, but that feels a bit weird.

No, there is not other way for this kind of object (adding control point closer to angle is the only "weird" way as you already noticed). Related https://blender.stackexchange.com/a/273773/2214

Womp. Oh well, thanks anyways

Well, yes, if your curve is 2D, and is declared to be 2D, at the top of  its Data tab > Shape panel. Then Blender knows how to mitre the corners:

(For curve Bevel profiles .. not for Curve modifier deformations)

Right :) +1 ... my memory goes shorter and shorter https://blender.stackexchange.com/a/253501/2214

@vklidu maybe you're just not frustrated by the behaviour of 3D curves as often as me :) But, is  there a sensible and general  3D mitring solution, without further parameters? Not sure..

By default a curve object is placed as 3D curve. For this kind of curve, there is not better way ... only by adding more control points closer to angle keep lines thickness, but you will always deal with the issue at corners. Similar, but easier you result with curve converted to mesh object and using Skin modifier.
If your goal is 2D shape, than Robin Betts's answer is your way :)

It is happening because Blender calculates same profile shape at each control point.
(Here I converted a Curve to a Mesh just for visualisation purpose.)

To keep curve "thickness" consistent - profile has to be changed according to curve's segments angle ...

... sadly, that is not happening in Blender for 3D type curve.

Under Curve Properties you can change Mean Radius, but since you can't specify X/Y radius separately - the fix in one direction destroys profile in second direction ... so, it is useless as well ...

For this specific shape it is just better to convert into a mesh, Inset Face, Delete and Extrude (or add Solidify modifier).


text:
Make fluid move around the edges of an object / mesh
I would really like to have a liquid move on top of the surface of an object. How would I do so?
I thought maybe you have sort of a force field on top of the mesh but I have no clue how to do that in blender.
Thanks in advance!

You are looking for fluid obstacles. To set an object as an obstacle give it "Fluid" from the physics panel and then choose "Obstacle" from the drop down menu.

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


text:
Face problem in cube, edit mode
im new in blender.
I have a cube and only move the edge, one face look good but the other.....
Its a bug or im doing something wrong?

Faces do not work well concave like that. Instead of one face at the end, split it into two, and it will work as you expect it.

Go into edit mode, and press A to select all the vertices. Press the spacebar and type in "Triangulate Faces," and that should fix the problem.
Blender sometimes has problems calculating bent rectangles (technically known as quads), because they can be made out of two triangles bent one out of two ways. Take this plane for example:
It can be made of either these triangles:
Or these triangles:

As you can see, both versions use the same exact vertex locations, but achieve completely different effects. However, Blender doesn't know which one to choose. In your case, Blender gets confused and decides to basically fold the weird looking face in half, instead of making it concave. By using "Triangulate Faces," you are basically asking Blender to turn each face into a specific set of triangles, so that way it doesn't get confused about the possibilities. In the end, your cube should look like this:
I hope I helped you, and let me know if you have any questions.
Happy Blendering,
Graves Broderick

Of course! Have fun learning Blender!

Would you mind marking my answer as accepted and voting it up to show others it works?

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


text:
Custom interlacing of left and right eyes
I have a custom 3D display which requires custom interlacing of left and right eyes images.
How can I customize the interlace stereo mode on Blender? Do I have to rely on python scripts?

What display do you have? Most displays support the side-by-side placement. Double check the display's settings

The display requires interlacing of left and right eye images. This interlacing however is very specific.


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Blender for the chemical structure visualization
I'm wondering how well Blender is suited for producing images from existing 2D (CDX, SMILES etc.) or 3D (PDB, XYZ, CIF etc.) chemical structures. Basically, the task is to convert a set of coordinates to a finite (e.g. a molecule) or a subset of infinite (e.g. a unit cell) graphical representation. Ideally it would be nice if a certain level of "chemistry awareness" would be present, such as typical interatomic distances, coordination numbers, atomic and ionic radii.
Is there an addon that can help chemists to use blender for their routine work?
There is a related question about crystal structure generation with Blender. I'm assuming that structure is already established.

I don't know of any addons specifically for those formats, but then again I never really searched. If there are any a simple google search should find them, iff there aren't, then any dedicated developer could probably write a simple Python addon for import easily, but I doubt anyone would be willing to just do it for free. Blender has been used for scientific visualizations quite frequently before so it seems very feasible

There is a lot that can be done with the animation nodes add-on ( https://github.com/JacquesLucke/animation_nodes ) or Sverchok ( https://github.com/nortikin/sverchok ). If you post sample data and an example of the kind of output desired, that might be enough to see if it can be done using those tools.

This answer may be of interest.

I'm very confident you can achieve what you want using Blender. Searching the web for "Blender for chemistry" gives you a number of hits including video tutorials and images what others did. Maybe this blog post is interesting for you:
https://patrickfuller.github.io/molecules-in-blender/
Furthermore I found an addon for PDB import/export:
https://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Import-Export/PDB

This looks promising, yet it seems like Atomic Blender addon is abandoned and hasn't been in development since 2013, and it only allows importing PDB files (which is still something). Anyway, thank you for the starting point, as for me having very little experience with Blender and 3D this is helpful!


text:
Synchronisation between Video and UI/Image editor
I am a  fresh Blender user. I started collecting training videos and some of them are very explanatory indeed. So I guessed, following their instructions I could manage. The problem I describe here is a problem I have with all the videos I shot with my Panasonic Camcorder  HC-VX870.
In this video, wanted to blur the ship floating on the river Seine.
System imformation :
Computer ASUS Desktop PC P30AD
Processor 4 Intel Core i3-4160 CPU @ 3,60 Ghz
Memory : 3914 MB
OS : Ubuntu 16.04.2 LTS
Specs of the video :
Duration :  1 minute 24 seconds
Container : Quicktime
Video :
Dimensions : 3840 x 2160
Codec : H.264 (High profile)
Frame rate : 25 fps
Bit rate : 61128 kbps
Audio :
Codec : MPEG4-AAC
Channels : Stereo
Sample rate : 48000 Hz
Bit rate : 256 kbps
Media details
Demuxer : lavfpref
Let us now take a look at  the process itself.
Step 1 : I add the video. It appears in the upper-right side window. Everything works fine.
Step 2 :  I open the UV Image Editor in the upper-left side window . OK.
Step 3 : I create my mask (upper-ledt side window). I call it Blur_01. OK.
Step 4 : In the Upper-left side window, I open the video. It appears. No sinc yet, but so far, so good.
Step 5 : In the Upper-left side window, I select View/Properties, in order to sync the left side and right side.

Step 6 :   In the Upper-left side window, I now tick  the Match movie length and Auto Refresh boxes… and the video disappears.

I have been trying hard over the past week to solve this problem, to little avail, so I am turning to you now.
I also tried on Blender 2,76. I managed to move my mask around in the UV Image Editor, then I ended up with two cases :

If I start from image 1 (say image 1 to image 50), everything seems t work fine and I manage to get full sync (i.e. the mask  moves around nicely in both windows).
If I start from another image (say image 51 to 100), then I cannot get the sync and, while the mask moves around in the Upper-left side window, it stays stuck at image 51 in the Upper -right side window.

I hope I clearly stated the nature of my problem. Thanking you in advance for your time and efforts.

It could really help if you try with the last version 2.78c because it could be a bug.

Hi, thanks for your reply. Actually, the version I am using is already 2.78c. Indeed, I had not noticed the (little) c coming after '2.78' in the opening splash window.

I lately tried with version 2.79 and faced the same issue. Too bad, as Blender seems to be the software I need. Thanks for your time and effort anyway. I'll keep trying...

I recommend you to convert the video to an image secuence, you can do it with Blender if you want, render the video without changes to a series of images. Anyway I prefer using ffmpeg to do this job, is free and you have lots of examples on Internet.
I think the problem could be that, as the video is encoded, a frame in the middle could not exist (completely) and this is why it can't show the image.

I just converted part of one of my videos (image 392 to 480) to an image (PNG) sequence. I got all the 89 frames complete, so none of them is missing. I did the same with another of my videos and again got a continuous sequence of PNG images, with none missing.

I also tried to convert some my *.mp4 videos into *.avi videos. It worked nicely but when I tried to apply the process I initially described, I ended up with the same issue.

@olivermassot the issue appears when you use the avi or the png sequence?

The issue appears when I use the avi format. Actually, sometimes the video simply does not appear on the Upper-left side window, or it freezes on one frame (as soon as I tick on the Match movie length box.

The problem with the avi is the same as you have before, encoded videos usually doesn't have all the frames as complete images and I always recommended to work directly with the image sequence strips.

I converted one of my mp4 video (4692 frames) into a sequence of 4692 PNG images. I managed to get full sync between the upper-right and left windows. So it works, but it is quite cumbersome.

Maybe you could submit a bug in Blender so they can improve it https://www.blender.org/support/


text:
Imported meshes look faceted
I have bought a few files from turbo squid, unfortunately for my needs some of the files look faceted.
Generally I will import them as OBJs.
I have tried using the the smooth and relax tool, but they don't help enough. I want to really add more nodes/vertices - at least i think that's what i want to do.
I have only ever used CAD programs before so Blender is completely new, if anyone could point me to the tool name or a tutorial I would appreciate it

Looks like that particular piece just doesn't have smooth shading applied.

Some imported object may contain "Sharp Edges" setting, you might need to clean it up in edit mode

I will be exporting this to use in a webGL application, so just chaning the shading is not sufficient, I want to actually change the model to be smoother. What is the tool required it edit mode to do such operations?


text:
Why video appears in lower left corner when offset is checked in strip transform parameters?
In my case I'm creating a movie with the resolution of 1080x1920 (9x16). I have footage that's 1920x1080 (16x9). My idea was to scale it to fit the dimensions of the movie. I thought I could do it with Transform Effect Strip. But the problem is that I need to enable Image Offset first.

When I checked "Offset", the video took its own aspect ratio. Why did it appear in lower left corner?

After I try to change the offset a little bit (just to see what happens), video seems to move a bit and scale up for no reason.

Next, when i play the result, it is actually showing that scaling was not applied.

From this point I'm already confused. I'm stuck because if I add Transform Effect it is scaling my video with the pivot point located somewhere in the center of the preview area, scaling it like this will send my video far outside of the preview area (it makes it nearly impossible to adjust scale with precision). I expected the pivot point to be in the center of the video.
What are the solutions to this problem?
Is it a bug? I heard people are struggling with similar problems since 2016!

Offset and Crop are working in pretty odd ways: https://developer.blender.org/T74323
The best way to deal with them is to use the Transform Tools add-on(until they're fixed):
https://github.com/doakey3/VSE_Transform_Tools
After installing, you'll find the Transform options in the Toolbar in the left side of the Preview:

(Btw. in order to get Transform Tools working, you'll need to update Blender to 2.83)
In the latest beta of 2.90 the bug you mention may have been fixed.


text:
Blender will crash when i use unwrap script
I want to use a script to add lightmap uv for all object in scene.
import bpy
context = bpy.context
#objects = bpy.context.scene.objects
objects = bpy.context.selected_objects

def AddUV(mesh):
        lm = mesh.uv_layers.new(name='lm')
        lm.active = True
        bpy.ops.object.mode_set(mode="EDIT")
        bpy.ops.mesh.select_all(action="SELECT")
        bpy.ops.uv.lightmap_pack()
#           bpy.ops.uv.smart_project(angle_limit=66, island_margin = 0.02)
        bpy.ops.object.mode_set(mode="OBJECT")
        lm.active = True

for obj in objects :
    if obj.type == 'MESH':
       context.view_layer.objects.active = obj
       obj.select_set(state=True)
       mesh = obj.data
       if len(mesh.uv_layers) < 2:
           AddUV(mesh)

when i select multi objects and click execute, the blender may crash

Have you try to print some data regarding the process ? How many objects do you have in your selection ?

Thanks for reply!
It seems to be because blender gets stuck in the unwrapping process and if a second model starts the unwrapping process it crashes.
Selecting 2-3 objects is prone to crashing.
Using an empty item and clicking on the script several times in a row also crashes.
Is there any way to make the cyclic process where one model finishes unwrapping before starting another

Can you provide more info about "if a second model starts the unwrapping process crash" please ? Can you share a file ?

https://drive.google.com/file/d/1tvRVNLCX41Ie532NcfsmXKxYsyfTNGAL/view?usp=sharing
open this file and select all object in scene, then run the python script, my blender 3.3.1 will crash.

Good news,
change this code then the blender work fine, not crash any more.
def AddUV(mesh):         lm = mesh.uv_layers.new(name='lm')         lm.active = True         bpy.ops.object.mode_set(mode="EDIT")         bpy.ops.mesh.select_all(action="SELECT")         bpy.ops.uv.lightmap_pack()         bpy.ops.object.mode_set(mode="OBJECT")         lm.active = False


text:
import script into __init__.py from subdirectory
I am struggling with importing a script from a sub sub folder
I have the __init__.py in folder X. Inside folder X there is folder Y and in folder Y is folder Z
I have a script in folder Z that I need to import.
To import from folder Y I use from .Y import script
Now I want to import from Z so i tried
from .y/z import script
from .Y//z import script
from .y\z import script

None of them works
How can I import scripts from folder Z?

from .Y.Z import script

Please place it as answer so I can accept it for you.|
Earns you some credits

Inside python , you refer to directories by placing . just like java, unlike C++.You should try from y.z import script instead offrom y/z import script.Moreover this is a very basic python problem, I'd recommend learning python for some time before jumping into making blender addons.


text:
FloatProperty not precise (bug?)
So I assigned a floatproperty inside my script.
As I moved along I noticed differences that was unexplainable. SO I started to check the properties and how the system take care of them.
Result is
  lenght1: FloatProperty(
        name="Lenght1", unit="LENGTH", default=40.0 / 1000,
    )

Prints as

As you can see, the property that is 40 became 39.9xx?
Any idea if this is a bug?
Since I do a lot of calculations this becomes an issue and some results get off by more then 1 which is a no no

A solution for this is to actually store strings instead of float values, and parse them every time you want to do calculations. (eg length1: bpy.props.StringProperty() and then length1 = "40.0") This is a very well know problem with computer calculations and optimization.

@Gorgious  Thanks for pointing this out. This indeed makes the precision a lot better.

It is not a bug. Floating point numbers are only accurate to about 8 decimals in Blender because it uses CPU single precision internally. Depending on what you mean by a lot you might want to investigate numpy which uses double precision internally.

Thanks for the reply. May I ask, As you see I made the property 40.0 and not 39.9
So what makes it change from my initial 40 to 39.9?

It's not 39.9 but 39.999999... which in 8 bit precision is equal to 40

Sorry I didn't reply sooner. I've been traveling.  @Gorgious is right.  It's a quirk of how floating point numbers are generated that they often end up being represented with repeating-last-digit representations.


text:
Custom operator menu
I am seeking for some examples to make a custom operator menu.
The operator menu that comes OOTB is

The more options you have the longer (higher) the menu will be.
I would like to make a menu that is wider (like vertices and radius next to each other instead of how it is in the screenshot.
See 2nd screenshot
I would also like to know if it is possible to make the menu interactive? Meaning that I would like to make a dropdown option that will let the user switch between multiple menu's for the same object.
Is all of this possible and are there any examples?
Thanks in advance

You would have to modify Blender's source code for any built-in operator to change the operator's adjustment menu; but you can create the details for your own operators using Custom Drawing. There's an example on that manual page.  You need to do three things specifically:

Add the invoke method's call to the window manager to pop up the menu.
Write the draw routine that draws the popup the way you like
Write the menu call function, but only if you want your operator to be included in a dynamic menu.

Thanks Marty.
I dont want to change the built-in operator. Only the one specific for my own add-on.
Will read the page you refer to and see how funky I can make my addon :-)

As funky as the UI will allow.  Basically the draw routine works like a panel draw routine so you have access to all of the layout options, including columns and rows. ;)

Could we have a chat somewhere? I might want to ask you 1 or 2 specific questions related to this subject. And if I keep posting it here I probable would be panelized?

You won't be penalized.  If we continue here in the comments, eventually stack exchange will ask us to "take it to chat" but I don't know how to do that manually, so ask away.

If I have a question I will reply here :-) But to learn good I need to try it myself first.  <-- You will not learn by asking without trying it yourself first -->

pls see screenshot.  I made an pull down menu and now want to change the menu depending of the choice made (https://prnt.sc/24uvc5j) but it does not work
I did different variations of this line <<--- if self.align == "Option 2": -->> But it does not seems to work at all. So it must be wrong what I am doing.
Is it possible to change the operator menu when you choice a different value from a dropdown?

That's a good question, but you're farther into operator menus than I've gotten. The answer is yes, but I don't know how.  I think there are questions on here that go into that.  try a "Search on Blender..." for something like '[python] menu' to see what comes up.

Let us continue this discussion in chat.


text:
Animation: Object following path slows down at end
I have a light object following a Bezier circle around a text object.
When I play the animation inside Blender I notice that the object slows down starting around frame 90ish.
I also would like to know why, when in repeat mode (meaning the animation keeps repeating from frame 1 tot end) the object halts for a split second.
Can both "issues" be solved?
I would like the object not to slow down at the end and if possible when repeating I would like to see a smooth motion.
I follow this tut and as you can see the light keeps going in 1 smooth motion.
https://youtu.be/jLqD2_cVdQM?t=201

Select all keyframes, then press V on the timeline and choose vector (or T > Interpolation > Linear). Then your animation speed is constant.

to have a "smooth" animation without the split just select the last keyframe

then press G 1

and enjoy your smooth animation:

or T > Interpolation > Linear

updated my answer ;)

Thanks. Please also add to your answer that pressing V needs to be done on both keyframes. (at least for me in V3.0.0)

you just have to select all keyframes...than one time v is enough....

Yeah thats what I meant :-) @Chris


text:
Trying to add details to a hexigonal base and im having consistency iussues
im a bit new to blender and im trying to model a hexigonal stand for a prop and i cant get all the details lined up like id like. placing them by hand is obivously not a good way to do it but i tried anyway and it looks really rough, the issue is i want them all to line up like a band surrounding the base of the stand with these raised bits at the corner and i cant get it to look right.
i tried orientating them with the topdown wireframe view but im certan i messed up somewhhere because everything is just a bit out of whack

You could do it this way:

Create a plane, in Edit mode scale it and move it away form its origin:

Give it an Array modifier, enable Object Offset instead of Relative Offset, create an empty at the same position as the plane center, choose it as Offset, rotate the empty 60° on Z:

Move and edit the mesh in Edit mode:

Extrude it, etc, when you'll be good, apply the modifier and Merge by Distance to merge the vertices:


text:
How to remove black background in rendered rgba png image sequence?
I rendered an animation in blender cycles and I set it to the following settings:

I waited for hours for the image sequence to be rendered into a transparent background image sequence, and yet the result was a black background!!!
May I know what did I do wrong?

Have you tried compositing your frames on a white background?

@HISEROD No I haven't. May I know how?

There are many ways to check if your alfa channel is working. You should be able to find what you need through a quick internet search or YouTube. ;)

@HISEROD Okay I will check. But if the alpha channel is working, what do I do next. Because I rendered 72 png images so that I can create them into an image sequence in blender's video editor.

You could put a color strip beneath your frames in the VSE to check if your alfa channel is correct.

@HISEROD I added a color strip beneath the image sequence in blender's video editor but still I have the same issue.

Let us continue this discussion in chat.

@HISEROD I did check whether there is an alpha channel or not. All the png images have an alpha channel

Make sure in the VSE, the image sequence which should have transparency is set to Blend > Alpha Over in Compositing, not Cross or Replace etc., also make sure in the Preview window that Display Channels is set to Color and Alpha, not Color. Have you opened an image of the sequence in a software like Photoshop etc. which can display transparency? Is the background black there, too?


text:
Combining Models that have already been finalized
So I have made a model in blender such as eyes with reflections, a body with fur, a glossy beak and now I want to combine them but when I do, It makes everything have fur and removes their original textures! I have tried everything.

Once you've combined everything, you need to edit the resulting mesh, select each of the original object's meshes and assign their materials to them one at a time.

ok thanks ill try that

How do i select the objects seperately if they are combined?

In edit mode, hover over part of the mesh from one of the original objects, and type L.  that is the shortcut for "island select".    Once you've done that enough times, stick it's material into a material slot, and hit 'assign' in the material panel of the properties editor.  Repeat as needed.

The fur can be limited by a vertex group/weight paint. Specify the vertex group as Density in the particle settings:  https://i.sstatic.net/cq1JR.jpg

After trying both of your solutions they worked except did not fix everything one of the eye is still covered in puff and the white hair is not there (I put the white hair using a rectangle and put hair on it). https://imgur.com/ivxm5CQ


text:
Why won't my objects change color?
I'm new to blender, so sorry if the wording of this is kind of vague. The objects color won't change and It is the color of the background. Also In render mode, it appears as a silhouette and only shows the world bg color.
[

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

That grid pattern on your object clearly tells that your object is transparent. Check your material settings if values like Transmission is set to 0 and Alpha to 1

The transmission is set to 0 and alpha to 1. Should they be something else?

Hi, it`s easier for us to spot the issue if you share your blend file, so please share it with the given link.  https://blend-exchange.com/

No problem, if you are unable to share it through blend-exchange then please share it through google drive.         https://www.google.com/intl/en_in/drive/download/

https://drive.google.com/file/d/1PVrgw4YXy5rUw7cmHsNeDGENxNafWioW/view?usp=sharing

@chance thank you so much :)

I rendered it and it turned out perfectly fine.  Have a look at it    https://drive.google.com/file/d/11yzQO6d9z1SHjTwgPo5CyDygBl5USyks/view?usp=sharing

I think my computer is the problem then. Thank you for your help!

Yeah probably that is the issue


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Blender -> UE5 UVs Breaking
I’m trying to import an .fbx with ~2.7M faces. My workflow is Blender → Zbrush → Blender (for size and pivot point fixes) → UE5 (I also use Substance Painter for texturing but it doesn’t touch the UVs). I’ve checked the UV maps at each stage in this pipeline and the UVs look correct in Blender (just before exporting it for UE5). When I import the fbx into UE5 however, the UVs break.
I feel like I’m probably doing something simple wrong. Here’s a visual:

I figured it out!  Need to triangulate the mesh before importing it into UE5 :)
My workflow was best to triangulate and export the mesh from Painter once I was finished painting, but I also could've triangulated in Blender or Zbrush.  I'm not sure when the "best" time is to triangulate but doing it in Painter seems to work pretty well.


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How Can I Make A Spiral Around A Cone
I came across this render by someone and in order to improve my skills, I decided to try it hands on but I am currently stuck on how to create that spiral mesh around the cone like object in the front. I have tried a number of stuff including using the bezier curve and simple deform modifier but I am not getting it right. Please help me.

That also seems to do the trick. I'll try it and see

@Emir This question is different from the one you cited, it is not a duplicate.

Yes, please. It is not a duplicate

https://blender.stackexchange.com/questions/193249/how-would-i-make-an-indented-swirl-around-this-sphere/193266#193266

You have to enable the curve: extra objects add-on:
then do this:

increase height, decrease radius growth, increase turns


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Exporting Conveyor Belt Animation for Unity
I modeled and animated conveyor just like in this tutorial. But I don't know how to export it. I would be glad if you help. Thanks. https://www.youtube.com/watch?v=ZDwxGPsfG6E

In Blender,you may want to go to your preferences and then add ons and enable Import-Export FBX.
This is what the documentation for unity says, and the link to it.
"Unity natively imports Blender files. This works under the hood by using the Blender FBX exporter.
To get started, save your .blend file in your project’s Assets folder. When you switch back into Unity, the file is imported automatically and will show up in the Project View.
To see your model in Unity, drag it from the Project View into the Scene View.
If you modify your .blend file, Unity will automatically update whenever you save.
Unity currently imports

All nodes with position, rotation and scale. Pivot points and Names are also imported.
Meshes with vertices, polygons, triangles, UVs, and normals.
Bones
Skinned Meshes
Animations"

https://docs.unity3d.com/560/Documentation/Manual/HOWTO-ImportObjectBlender.html


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How to seperate legs from each other and sculpt?
Well I want to sculpt genitals for my models but I dont know how to do that. I mean what is the method for it? Because I have to seperate them and work there but I couldnt find any way to do that. Can you show me some method?

So, the problem is, we want to sculpt, but the legs are in the way, so we can't easily sculpt what we want to sculpt?  There are a number of solutions to this problem.  They all work slightly differently.
One thing we can do is mask the legs for purposes of sculpting.  We can select a mask brush, then sculpt over the legs with that brush, making them progressively more transparent.  If we do that, any further sculpting we do (with regular brushes) won't affect the masked areas, to the proportion that we've actually marked them with a mask brush.
For a less gradated approach, we can just say, no, just don't sculpt the legs!  Period.  No, exclamation mark!  Tab into edit mode and select a bunch of leg verts and 'h' to hide them.  Now switch back to sculpt mode and start sculpting, and we'll see that our sculpting doesn't affect any of the vertices that we've hidden.
Okay, but let's say we don't even want to see the part of the mesh that we aren't sculpting.  We can do that; let's use a mask modifier.  Same thing as before, tab into edit, select a bunch of leg verts, and assign them to a new vertex group.  Then give the mesh a mask modifier, specify your vertex group to modulate that modifier, click the button to the right of the vertex group in the modifier to invert that group, and we're now hiding all those verts.  We can't sculpt them, and we can't even see them.  Tab into sculpt mode and you won't see or affect those verts.  But, you can't dynotopo at that point, because Blender won't know whether to assign dynotopo verts to the masked vertex group or not.
Are there any other ways to do this?  Sure!  We could separate the legs out to a new object, then sculpt, but, careful not to sculpt the margins, and rejoin later.  Or, we could sculpt a whole new object, then boolean union it with our original mesh.  There are a ton of different techniques.  Each one is slightly different in how it works; it's best to understand all of them so that you can use whichever is going to make your current problem the easiest to solve.

Thank you so much! Can I move legs without rigging them? Like move them and sculpt than take back to their last position? Sorry for my english btw.

Taking them back to their last position is the hard part, and I'd recommend just rigging them if you need to do that.  Otherwise, yes, you can move them with a pose brush.


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What is this tool name and how can I select it?
At this video at 16.50 He/she use some tools to move verticles like sculpt grab tool but I couldnt find that tool what is tool name how to select it can you help me?
https://youtu.be/DbGN7d6EiUA?t=1010

I think he has just activated the Proportional Editing option

he move verticle with circle is that so

if you enable Proportional Editing it will display a circle that will show you the influence radius of the option, you can change it with the mouse wheel I guess

This is the proportional editing. You can enable it via its button at the top of the viewport:

For more information, see Blender Manual - Proportional Editing


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Soft Body Loop Reset At Frame 1
I have a character with soft body and I want to make simulation loop but every time when it goes to frame 1 simulations restart so it brokes my forever loop. How can I make loop and prevent simulation reset at frame 1 because it brokes my loop.

This is totally normal behaviour that the simulation restarts at frame 1. What did you expect? that it continues when it jumps back to frame 1? If you want to make a loop animation, just make sure that in your simulation your last frame looks exactly as frame 1. By this you will get a looping animation.

You will only get a looping animation in Blender if you make sure that your last frame of your simulation looks the same (or nearly the same) as your first frame. Only by this you will get a looping animation.
Of course any simulation (rigid body, soft body or whatever) will restart at frame 1 (or at that frame the start frame of the simulation is set)


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Seamless animation loop
I'm trying to animate 2 character having hot time(nfsw). My problem is whatever I tried I cant make my animation loop seamlessly. I have tried to make my frames 1 less frame. For example my animation 1-24 I made it 1-23(end frame) but it didint worked. Also I have tried to choose all key frames and use linear or cycle modifers but none of them working. What Im doing wrong? Pls dont fix my problem teach me what is wrong and what should I do.

Also I can share blend file but I dont know how

https://blender.stackexchange.com/questions/141712/how-to-create-a-seamless-animation-loop-in-blender?rq=1

https://blender.stackexchange.com/questions/7912/looping-walk-cycle-animation-snaps-back-on-repeat?rq=1

I probly checked every topic about that and I saw your links before already.

Hard to tell without blend file. The things you say you already tried should have worked in one way or another, so I can only imagine you did them somehow wrong - but there's not enough information in the question to determine what exactly is wrong.

How to share a blend file


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Cloth shape key location change
I created cloth sim and it works fine but when I use cloth modifer ''save as shape key'' option my cloth change place. I basicly disable cloth modifer and use shape key but my tshirt changes location or rotation. What causing this what I'm missing can you help me?

hello, maybe share your file (only the shirt) so that someone can check?

I want to know theory behind this. I dont want to solve it for just only this file. I want to learn than I can fix my all problems about clothing. Do you know why this is happening? I tried to ctrl A apply all transforms maybe it fixes but it didint.

Don't worry, people that figure out the problem will explain as best as they can, rather than just fix it and send you a file.  But there are usually enough potential causes for a problem that figuring out the cause requires some investigation.  That's why providing a file would help get your question answered.


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Multiple Shape Key Driver
Im just new to drivers I figure out how to do it with bones but when it comes to multiple shape keys Im bit confused and need help.. For example I have 1 shape key that works with bone it makes skin close the finger but it is clipping so I need another shape key to fix first shape key. Problem is I don't know how to use it together with first shape key. I mean when I move bone first shape keys works but second one is so slow.. It has to be become 1 to 1000 value faster to work but I don't know how to do that.

You should post screenshots and/or upload a blendfile to help us understand your issue a bit more clearly.


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Is it possible to make so the wind starts from some particular plane and doesn't affect anything behind that plane?
I have a single image of a coat that I am trying to animate. Wind and cloth effects are what I need but the problem is I want to set 4 different sources of wind for different directions and make it so the wind blows from its own plane and doesn't affect anything behind the plane

ok, found it nvm. In physics properties there is a Z direction option

Okay, I was just about to write an answer ;)

@Jurby Please add this answer to your own question so it will not remain in the unanswered list, and later researchers can find it.

@TheLabCat sure

Found it. In case somebody stumbles upon the same problem. Click the wind object -> then Physics Property tab --> in Falloff section choose Z Direction to +Z. The wind now blows strictly "from" the wind emitter in direction of the normal, not from behind.

Hi, thanks for the post. This site is not a regular forum, answers should be substantial and thoroughly explain the solution and required workflow. One liners and short tips rarely make for a good answer. If you can [edit] your post and provide some more details about the procedure and why it works feel free to restore it, otherwise it may be deleted or converted into a comment. Perhaps add a few images illustrating the workflow and final results. See How do I write a good answer?


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TBSCENE extension
I stumbled upon a 3D model that has this .tbscene extension file. In general, the folder with the model has an .obj file and a .mtl file. The thing is .mtl file doesn't specify any texture files, so when I import the .obj file into blender the model is just grey with a default material. But that weird .tbscene file has all the references to Normal Map file, Gloss Map file etc. I don't know how to use it so blender know what the heck is going on. Need help

According to Google that's a "Marmoset Toolbag" file. The only information mentioning Marmoset here is this  which is 3 years old and doesn't mention that file extension at all.


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Plane doesn't mirror correctly
Hey,I'm trying to retopologyze the head but I can't do it because the plane doesnt mirror correctly

hello, please share your file: https://pasteall.org/blend/

Does this answer your question? Symmetrize option doesn't mirror bones on the axis

The origin (orange dot) is the center of the mirror. Right now, it's in the middle of the created plane. You need to move the origin to the center of the head where the mirror should start. There is an option to move it => https://blender.stackexchange.com/q/165421/107598


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How can i sculpt with mirror modifier
I want to sculp some eye sockets but it doesnt sculpt properly. It only does work when i apply the subdivision surface and mirror modifier

to be able to sculpt you need a bit of topology, do you have enough? if not, either enable Dyntopo or subdivide your object (you can subdivide if you apply the Subdivision Surface)

as for the Mirror, it seems that you can't see the result in Sculpt mode, so as Emir says use the sculpt mirror and symmetrize tools

You don't need a mirror modifier, there is an option called symmetry to sculpt. There, you have an option called Mirror.

I can only see two ways to get this to work the way you want. Either apply the subdivision surface modifier (not optimal) or using a multi-resolution modifier, not a subdivision surface/mirror modifier combo.

Apply your Mirror Modifier. You need to do this if you want to sculpt on a mesh that is subdivided by a modifier.

In sculpt mode, turn on mirror sculpting in the symmetry tab. This will act as your mirror modifier instead.

Remove your subdivision surface modifier and add a multiresolution modifier to your scultping object. Press the subdivide button to increase the subdivisions. You can also scuplt on different levels of detail using the scuplt attribute. This modifier can do a lot, read up on it here or search some videos on youtube.


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How to make camera cover the whole screen
How can i cover the whole screen because i want to make a render of the full room. I tried to do this with changing the resolution but at some point it stops

Just pull the camera object back.  If needed you can adjust the clipping range to peer through walls

agree with @AllenSimpson, and you can also adjust "Camera" >> Size, and Focal Depth


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Why does it render the same frame

Im trying to make 360 degree turntable animation.When i hit play in layout it rotates,thats what i wanted but when i hit render Animation,it only renders the first frame.Here is for example the first and last frame

You may need to uncheck "Placeholders" and check "Overwrite" in your Output settings. If you have already rendered frames from any blend file, that is preventing new frames from being output to your tmp directory. After changing that, use "Render>Render Animation" to render the sequence, then "Render>View Animation to play the rendered sequence.

Still doesnt work but i noticed something, the light rotates on the donut when i hit View animation

Are you not in Object mode when you hit the Render Animation button, or is there a modifier or an object/collection that has it's render visibility disabled? If you can attach the file that would help a lot, I need more information to make another suggestion.

Yeah i had to convert the particels and apply but now the sprinkles arent moving, should i Parent them to the Torus ?

Sounds like it.


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How can i make the color of the texture the same as the hand?
I'm trying to make the brown of the texture blend in with the hand but i can't get it right, i also put the same values for the two colors

You'll need to pack the resources into the Blend file (File > External Data > Pack Resources and save file) and upload it here again before we can see the image with the ace of spades decal on it. I presume you're talking about the difference between the background colour on the image and the Material.026 colour you're using for the rest of the body? You should be able to just use the eyedropper from the colour palette to copy the colour from the decal in the 3D view into your material Base Color.

The difference in colour is actually caused by the differing reflective and anisotropic properties of both the spade and body materials. A quick fix would be to use the exact same settings for the skin across both. Your mistake was to use a standard Diffuse shader as a stand in for a Principled BDSF (See the first screenshot).
However copy and pasting the same shader across isn't ideal because if you want to update your skin material later down the line you'll have to update it in multiple places.
To avoid this you can group your skin texture and then instance it in your hand material. That way, any updates you make to your Skin Material will automatically update the spade (see second screenshot).
There are a few approaches you can make to recreating something like this in future. UVMapping and 3D Painting are two techniques that unlock huge potential for customising the look of your models and will add flexibility to your workflow.


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Getting grey spots on eye
Im getting these grey spots on my eye in the render preview. i read that i have to flip or recalculate normal but that doesnt chnage anything, i also tried to apply everything. I used a Outline addon, is it because of this ?

It's because of the Solidify Modifier. There are two issues with it and the result is that the modifier creates the new geometry in exactly same place as the original geometry of the eye. So, you have overlapping faces with opposite normals.
Here the two issues:

The Vertex Group you are using for the outline is actually empty. So there's no effect.

once (1) is fixed:

Increase the Factor (below the Vertex Group in the modifier) at least a little bit, because when the Factor is at 0, the geometry that's not in the vertex group will still create new and overlapping faces.

After that, everything should work fine. :)


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Bald spots on model with hair particles
I wanted to add fur to this model but there are some bald spots for some reason. Any ideas on how to fix this ?

It looks like for some reason the ngon you have at the top of your mesh, coupled with the Subdivision Surface modifier, make the particle fail, you can fix that by creating quads:

Or enable the Use Modifier Stack which seems to fix the problem:

Or move the Subdivision Surface modifier below the ParticleSystem, but it may look bad:

I also would apply the scale (Ctrl+A > Scale in Object mode) since it's non-uniform, and set Render Properties > Curves > Viewport Display > Shape to Strip so you can see the rendered shape in the viewport.

@Blunder thanks for the additional infos  ;)


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Security Popup about a Driver when Appending a Material
Every time I append one specific material from my library, I am given this error:

I usually just ignore it and continue on my merry way. However today I decided to fix it. I don't know anything about drivers currently, other than that they simply allow you to modify the behavior or settings of one object to another using some kind of formula. I've gathered that 'water_drive_xtm(self)*(var/100)' is the formula in question.
Here's a gif that shows where the driver formula resides in the material:

Does anyone know what this script is actually doing? It's a water material if that helps.
How do I remove the driver so I stop getting these warnings?

Edit: Here's the blend file if it helps explain what the driver is doing:

suggest still images of node trees rather than gifs. Gifs are not needed here. Also, for future reference there is an edit history that explains the edits made, it is not needed to explain your edit when you make an edit to add information, image, file, etc...

You can right click it and hit Delete Drivers.
It looks like it's randomizing the origin location of the noise textures hooked up to the bump map to give it a more random appearance based on whatever parameter that driver was looking at.

Thanks, I deleted the drivers and it still looks fine, so.. whatever :)

It's a thing where if you had a bunch of them it would become pretty apparent that they were a repeating object.


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Problems with Using Substance Designer Height Maps
I realize this question also deals with software other than Blender, but it's mostly a blender focused problem.
I am trying to figure out how to correctly set up displacement / height maps exported from Substance to Blender. Here is my node setup:

As you can see, the displacement is horrible. It's coming apart at the seams (black spots) and just generally looks horrible. This is what the material should look like:

So my question is the following:
What is the proper way to import and set up substance designer maps in Blender?
Is there an add-on that handles this automatically?
Is my node setup the proper way to do this?

Go to User Preferences > Addons, search for and enable "Node Wrangler".

Once you have it enabled, when you are in the shading tab, with the Principled BSDF selected, press Ctrl + Shift + T. This will allow you to load a whole PBR set at once (navigate to the folder and select multiple files). It works fine with Substance Designer's default naming scheme, except I think it has trouble connecting the BaseColor. You can do this by pressing Ctrl + T with the BSDF selected to load a single image texture connected to the basecolor and then choose your image that way, or you can Shift + D duplicate one of the other image textures, load it that way.

This shortcut method sets up the displacement for you, however how much of an effect it has in EEVEE is somewhat a topic of debate (as far as I know, it's not supposed to do something, but it does - but not always the best result). Instead, I sometimes prefer to run my displacement through a Bump Node. Either way you choose, also note that the default strength of 1 (on any of the bump/displacement/normal nodes) is often too high and gives undesirable results. I've sometimes needed to go as low as 0.1 before it looks right.

As a side note, make sure to make use of the Scale values of the Mapping node - I find many textures exported from Substance are scaled too large (1/4 tiled or so) and benefit by scaling by at least 2 or 4 on the X and Y.

Thanks for all that info. I didn't know that Node Wrangler could automatically set up your entire PBR texture set like that. Learn something new every day. :) Anyway, I actually think I pinpointed my displacement problem down to a lack of geometry. In order for the displacement to work correctly, I need a finely subdivided mesh (which my material preview ball isn't). But I really appreciate your thorough answer!

Make sure to use the experimental features and a subdivision surface using Levels to subdivide. It's adaptive (how far you are away from the camera) and non-destructive.


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Is there a simple way to highlight a selected node line connection?
I am working on a slightly complex node group, and I'm having trouble distinguishing various connections. Is there a way to select and highlight a node connection so it's easy to see where its inputs an outputs are connected?
Here's a quick mockup of what I'd like:

Open to add-ons as well if this isn't doable in vanilla!

While I don't think it's possible already, although it was proposed, you can make it a bit easier by pressing Shift and dragging over a line to create a Reroute node to make connection out of several parts (if Node Wrangler addon enabled).

Ahh. thanks for the workaround.


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How can I set default values for the Principled BSDF shader?
It's pretty simple, I just want to be able to make it so when I add a Principled BDSF Shader, that the "Base Color" (or any other value for that matter) is always set to pure white, opposed to off-white by default.
When you right click the color, there is no option to set as default value.
Any help is appreciated!

Not an answer, keep in mind that "pure white", or a material that has a reflectancy of 100% is not a realistic one. Most "white" objects in the real world have a reflectancy (or albedo) of 70 to 80%, in case you are wondering why blender uses that as default.

Yup, I knew that. The color is somewhat irrelevant to my question, I just want to be able to define default values. Thank you for the response.

You need to create the shader through a custom scritp that sets the values, else you can modify the source code for blender.

https://blender.stackexchange.com/questions/98294/custom-default-settings-for-nodes-materials

Create a group with principled and set the inputs of the group with wanted default values (you'll only loose access to distribution and scattering).


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Should I be using the Decimate modifier or Remesh modifier in order to simplify this model?
I downloaded a free bust from Turbosquid that comes in STL format:

So I imported it and for obvious reasons it has over 2 million tris. I want to ultimately use it in architectural visualization scenes as a decoration, so I need to simplify the model drastically.
Should I be using the remesh modifier here, or the decimate modifier? I know they both have their place, but I'd like to know what would be the best for this kind of use-case.
Thanks so much for any help.

Neither. In Object Data Properties, under Remesh, try the QuadriFlow Remesh. It's pretty amazing!

Awesome, I'll give it a shot today! Thanks.


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Is there a way to increase armature performance on a high-poly character for sculpting?
I am attempting to sculpt some corrective shape keys on my high-poly character, however the armature is seriously impacting my sculpting performance.  I have attempted to migrate my character to Zbrush to do my sculpting there, however all of my attempts to sculpt my shapes there have not managed to work.  Is there a way to improve the performance of the armature so I can create my corrective shapes?

Is there a reason why you try to rig the high-poly character and use corrective shapekeys on top of that? High-poly mesh + rig and high-poly mesh + shapekeys are both bad ideas because it results in very bad performance. The common workflow is to create a low-poly version, bake the normal map, rig the low-poly version and use corrective shapekeys for it if needed.


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UPBGE 0.2.5 Viewport Rendering
I working a project in UPBGE 0.2.5. But i have a problem. My Map is Big and UPBGE Rendering all map. is there a way to do "Use Viewport Render" which is an UPBGE 0.3 feature in UPBGE 0.2.5???

i found my question answer in 0.3. but i want to do it on 0.2.5. version.  video link :https://youtu.be/JHpTFRZjl60

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.

my question is: my map is so big and tiring upbge system. i want to do the youtube link. if you watch, you understand the my question. system invisible the hidden places. i afraid


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using real world images to add textures to cad models
I have a 3d scanner that can also record texture, however if i have it set up to a resolution that provides the accuracy that i'm looking for then the file sizes are simply too big. Parts that i am scanning range from 0.5m to about 15m. I would like to use textured 3d models for some augmented reality purposes, but at the moment i can't because of the file size. In the scanner software the texture is stored as a .bmp file. The texture i can only export as a .bmp file but the mesh i can export in various formats. When exporting in some formats the .bmp file is automatically also exported as well as a .mtl file for mapping the texture to the mesh. Is there a format or way in blender that i can load a model with the texture and then replace the mesh with a reverse engineered cad model (significantly smaller) and also at the same time massively reduce the file size of the .bmp file? To give an example a merged and textured scan of a "dome-shaped" component with a base diameter of about 3m and a height of about 1.5m is about 16gb of which the .bmp file is approximately 8gb. I need to get to a textured 3d model that is of a file size that is hopefully in the megabyte range rather than gigabytes. I am also open to suggestions how i might be able to use blender to load a reverse engineered model and add texture by wrapping the model with a few pictures if that is possible.

Unfortunately Blender is not yet very capable in dealing with point clouds from laser scanners. However CloudCompare (open source) can do some crazy things. Documentation is pretty sparse but the features are really simple to use, you just have to understand where to click. Try https://www.youtube.com/watch?v=MS3Krxcy2j0 or https://www.youtube.com/watch?v=m43usERF33M or https://www.youtube.com/watch?v=PcrcoocYSlU

I'm sorry, I have no experience in 3D scanning and .mtl files. But for the file size of the .bmp file: as soon as you have a model in Blender and the image is somehow mapped onto it, I guess there is an Image Texture node somewhere in the material using the bitmap. It should be no problem to replace the .bmp file in the node with some other file format like PNG, JPG, TIF etc. which is significantly smaller than BMP. If you use for example IrfanView to create a JPG, it is usually a much much smaller file than a BMP or even a JPG saved by Photoshop while still having a good quality.


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Units in Blender don't match units when 3D printing. What am I missing?
I've recently started modelling in Blender and I while I've been able to find answers for most of my questions, this one is eluding me.
So, I set my Scene scale to Metric, unti scale 1.0000, Length in Cm. So far so good. I modelled the object and when I check item properties the units are indeed in Cm and the length is correct. Yet when I export the object for 3D printing the units always come up exactly 100x smaller. So the object is 0.51 Cm wide instead of 51 Cm wide.
Is there a step or a setting I'm missing?

If it's exactly 100x smaller maybe set scale to 100.0000?

If you're missing a step it's possibly in the export process or the setup of the 3d printer's slicing software, I suspect.  Many file formats used by 3D printers don't have scale as a file format property.  What format are exporting and what slicer are you using?

@MartyFouts I'm not doing the slicing myself, merely uploaded the design to a few 3D printing companies' pages to try an get a quote. I exported as STL file. But the funny thing is that I get the same problem if I just open that STL in something like FreeCAD, so I don't think it's slicer-specific but more to do with something I'm doing in Blender.

So I followed @Gordon Brinkmann advice and tried playing around with unit scale. That by itself did nothing at first, no matter how much I scaled up or down, but once I switched the Length measurement to Meters AND applied a 1000x scale to the whole thing it finally worked.
An alternative that I also found was to keep things as they were and use the "Scale" option when Exporting. Seems that that scale actually changes something deep in the model that makes the slicer read it as a larger entity.
Thank you all for your replies, I think I have a workaround now even if I don't understand where the problem comes from apart from that Blender has no units even though it does.

This is quite "normal" and I experience it with my blends on a friend's 3D printer as well, since different softwares and file formats store and interpret mesh data differently.
Let's say Blender stores the value 0.51 for the length and your Blender Scene Properties > Units are set to Unit System "Metric" and for the Unit Scale "1.000000" then it tells Blender that the length is 0.51 meters.
Now another software only gets this value 0.51 but no information like scene properties, and if it usually works with 1 centimeter as scale base then this value is interpreted as 0.51 centimeters.
All in all, the Scene Properties setting for the Unit System and Unit Scale also reveal what this size in Blender really is: a more or less arbitrary choice. I think some physics simulations use these real-world scales for calculating more realistic results.
No matter it's no real size - in the end, if you look at the default cube: if you have Blender set to "Metric" and a Unit Scale of 1, then the cube is 2m * 2m * 2m.
But without changing anything on the cube itself, no scaling in Object Mode or Edit Mode, as soon as you change the Unit Scale to 0.1, the cube suddenly is smaller, 0.2m * 0.2m * 0.2m.
Or changing the Unit System to "None", the cube is 2 * 2 * 2 without any dimension. So what you can do (since you know the printing software scales the mesh down by factor 100), you could set the Unit Scale to 0.01, in this case all dimensions of your object will be shown in the size at which the printing software interpretes it.

I'm one that tries to improve things, which is pointless and I will erase my reply, I can see that is serves no purpose. No improvement will result from it. I did not intend to bother you personally with my post and it is not a problem uniquely Blender, all 3D printing software has the problem that scale is not obeyed, standardized or even included in the Format.

@MarkusBawidamann It is okay trying to improve things, but this site is not run by developers so it is the wrong place to plead for improvement. We are here just to help with how the things are at the moment, not how they should be.


text:
How can I rename packed image files and then unpack all with new names?
I recently purchased a few scenes from BlenderMarket, but the textures all have nonsensical names, or names that would easily cause conflicts (like 002.jpg). I've been manually unpacking and renaming the texures, and then replacing them in the scene. Unfortunately this process is taking forever.
Here's an example.
Original Textures:

Renamed Textures (What I did manually):

What I really need is a way to automate this process, or just a less time consuming way to do it. If I can rename the textures packed into the file directly in blender, that would be awesome. Or if someone could point me to a script or addon that does this, that would also be great.
Thanks much.

My workflow for handling texture images is to first pack all the images into blender. Then rename the texture name and then unpack the blender file with correct texture names.
However there is a caveat here: An image in blender has a name and file name. The image name we see in image node in shader graph are referring to the name of the image. When blender unpack the file, it uses the file name for writing to disk.
We can inspect the file name in Outliner, Data API panel.

I made a little snippet for renaming the file name to match the image name. You can run this snippet under Python Console panel.
for image in D.images:
    fp = f"//textures\\{image.name}"
    image.filepath = fp
    for pf in image.packed_files:
        pf.filepath = fp

Before running the script, make sure:

All image name are unique
Image name got their extension included
Make a backup

After running the script, do an unpack and the image filenames should align with the name shown in blender.
This is tested on Blender 3.0, Windows.


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Inconsistant behavior when re-linking missing textures. sRGB and Non-Color mismatches
I am having some trouble when re-linking image textures that have single user copies using different color spaces. I.E. A texture being used multiple times in the file, both in Non-Color and sRGB color spaces:

Create two objects and assign a unique material to them.
Plug in the same image texture into the base color of each object, but make one of them a single user copy set to "Non-Color" instead of "sRGB".
Rename the texture on disk to something different to break the links.
Point your materials to the new texture on disk.
Notice that your single user copy is no longer a single user copy. If you change the color space to non-color, the other material will change too.
This can be mitigated in simple scenes by making another single user copy. But if this material is used all over it can quickly become a nightmare trying to remember what was supposed to be sRGB and what was supposed to be non-color.

I can provide more images if any of this is confusing.
Is this working as intended? Or is this a bug? If I make a single user copy, I expect that datablock to function independently from the copy. But the process of re-linking the texture breaks this.
Any help would be great. Thanks!

Hello :). Not sure I understand. How exactly do you "4. Point your materials to the new texture"? I don't think Blender can directly replace a missing image with a different one.

Hi! Just click on the small folder icon: https://i.imgur.com/PjVJbdG.png

Oh, ok :). 'Single user' is assigned to the image texture, so when you load a new one, Blender doesn't know it's supposed to be a single user copy. But you can get there using RMB > Remap in the Outliner. I can post a full answer when I get home :).

That would be great. Thank you!

When opening a new texture, Blender doesn't know it's meant to be a single user copy.
You should Remap the old texture instead, so it'll change for all materials at once.

Add your 'new texture.jpg', with a second copy (new texture.001) for the non-color variant
Open Outliner > Scene
Right click the 'old texture.jpg' and go > Remap users > 'new texture.jpg' > OK.