Some hair particles are rendered the wrong material in EEVEE #78845

New Issue

Tiago Marinho · 2020-07-12T04:36:31+02:00

Tiago Marinho commented

2020-07-12 04:36:31 +02:00

System Information
Operating system: Windows 10
Graphics card: GTX 1060 6GB

Blender Version
Broken: 2.90, ee5c2f6ead, master, 2020-07-11
Worked: 2.83.2

Caused by b18c2a3c41

Short description of error
there are 3 planes, each plane has two particle hair systems. the particle hairs that on the same plane has the same material.
in blender 2.83 LTS. the color display as intended. since 2.90, when both hair system are active, the color is mix with others of different planes and different materials. if either one of the hair systems that on the same plane is disable, the color return to normal. in 2.83 it looks right, but in 2.90 and above, the blue and green materials also mix with red somehow.

Exact steps for others to reproduce the error
open attached blend file in 290 and above, switch to preview render to see the color mixed within different materials.
change the color_ramp.interpolation to different type from each other would fix the issue, for example, mat1's color_ramp.interpolation to linear, mat2's color_ramp.interpolation to ease, mat3's color_ramp.interpolation to cardinal

particle hair color.blend

Short description of error
Some of the hair particles (the right eyebrow specifically) in the provided file are shaded with other material, unless some of the other objects are hidden (the left eyebrow or both eyelashes)**

Exact steps for others to reproduce the error

Open the attached .blend file.
Make sure viewport shading is set to Material Preview Mode.
Notice the hair of the object to your right is rendered with the wrong material in EEVEE.
Disable "eyebrow scalp.R" from the viewport.
Notice that the eyebrow that was previously being rendered with the wrong material is now correct.

Note that this is not the same issue as described in this issue , the provided file used to work on older blender versions and the scale of the objects is always positive.

hair_material_bug.blend

**System Information** Operating system: Windows 10 Graphics card: GTX 1060 6GB **Blender Version** Broken: 2.90, ee5c2f6ead37, master, 2020-07-11 Worked: 2.83.2 Caused by b18c2a3c41 **Short description of error** there are 3 planes, each plane has two particle hair systems. the particle hairs that on the same plane has the same material. in blender 2.83 LTS. the color display as intended. since 2.90, when both hair system are active, the color is mix with others of different planes and different materials. if either one of the hair systems that on the same plane is disable, the color return to normal. in 2.83 it looks right, but in 2.90 and above, the blue and green materials also mix with red somehow. ![283LTS.jpg](https://archive.blender.org/developer/F9928445/283LTS.jpg) ![290Above.jpg](https://archive.blender.org/developer/F9928446/290Above.jpg) **Exact steps for others to reproduce the error** open attached blend file in 290 and above, switch to preview render to see the color mixed within different materials. change the color_ramp.interpolation to different type from each other would fix the issue, for example, mat1's color_ramp.interpolation to linear, mat2's color_ramp.interpolation to ease, mat3's color_ramp.interpolation to cardinal [particle hair color.blend](https://archive.blender.org/developer/F9928444/particle_hair_color.blend) **Short description of error** Some of the hair particles (the right eyebrow specifically) in the provided file are shaded with other material, unless some of the other objects are hidden (the left eyebrow or both eyelashes)** **Exact steps for others to reproduce the error** 1. Open the attached .blend file. 2. Make sure viewport shading is set to Material Preview Mode. 3. Notice the hair of the object to your right is rendered with the wrong material in EEVEE. 4. Disable "eyebrow scalp.R" from the viewport. 5. Notice that the eyebrow that was previously being rendered with the wrong material is now correct. Note that this is not the same issue as described in [this issue ](https://developer.blender.org/T68548), the provided file used to work on older blender versions and the scale of the objects is always positive. [hair_material_bug.blend](https://archive.blender.org/developer/F8693745/hair_material_bug.blend)

Tiago Marinho commented

2020-07-12 04:36:31 +02:00

Added subscriber: @tiagomeraki

blender-admin commented

2020-07-12 04:36:31 +02:00

#87379 was marked as duplicate of this issue

blender-admin commented

2020-07-12 04:36:31 +02:00

#85973 was marked as duplicate of this issue

Germano Cavalcante commented

2020-07-14 16:28:43 +02:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-07-14 16:28:43 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Germano Cavalcante commented

2020-07-14 16:28:43 +02:00

You forgot to attach or pack the eyebrow density.1001.png texture.
So when we open the file we don't see any particles.

But after I deleted the texture I could see the problem.
Here the simplified file:
hair_material_bug.blend

I will edit the description.

You forgot to attach or pack the `eyebrow density.1001.png` texture. So when we open the file we don't see any particles. But after I deleted the texture I could see the problem. Here the simplified file: [hair_material_bug.blend](https://archive.blender.org/developer/F8693745/hair_material_bug.blend) I will edit the description.

Germano Cavalcante changed title from ~~Some hair particles are rendered as black unless some objects are hidden from viewport in EEVEE~~ to Some hair particles are rendered the wrong material in EEVEE

2020-07-14 16:33:55 +02:00

Tiago Marinho commented

2020-07-14 17:54:43 +02:00

My bad, I was pretty sure I had packed this texture into the .blend. Thanks for taking the time and fixing the file. Next time I'll make sure to test it at another path before submitting the bug report, and take more time getting it to a minimal state and easy to test with as you did.

Ben commented

2020-10-27 10:29:32 +01:00

Added subscriber: @nimajneb7

Ben commented

2020-10-27 10:29:32 +01:00

I've been having this issue as well.

If two hair systems use materials with the same node layout, they will render the with same material, even if the two materials have different values or textures.

I've been having this issue as well. If two hair systems use materials with the same node layout, they will render the with same material, even if the two materials have different values or textures.

Oleg commented

2020-11-09 19:14:27 +01:00

Added subscriber: @agorka

Oleg commented

2020-11-09 19:14:27 +01:00

I'm having this problem too, tested in 2.90.1, 2.91 and 2.92.0 Alpha
Uploading another example. Hiding red eyebrows makes upper eyelash render correctly in black. Bug happens only in eevee renders, cycles handles this correctly.
Also, duplicating eyebrows and changing hair material of one of them to black changes lower eyelash color to red.
Something really weird happens there.
Head0002_hairmaterialbug.blend

I'm having this problem too, tested in 2.90.1, 2.91 and 2.92.0 Alpha Uploading another example. Hiding red eyebrows makes upper eyelash render correctly in black. Bug happens only in eevee renders, cycles handles this correctly. Also, duplicating eyebrows and changing hair material of one of them to black changes lower eyelash color to red. Something really weird happens there. [Head0002_hairmaterialbug.blend](https://archive.blender.org/developer/F9247118/Head0002_hairmaterialbug.blend)

Oliver Feiler commented

2020-12-27 10:16:23 +01:00

Added subscriber: @Keeya

Oliver Feiler commented

2020-12-27 10:30:38 +01:00

I have encountered this bug with multiple objects that use multiple hair particle systems and materials. If your object has multiple material slots which the particle systems use, it goes haywire.

I have this test case:

object "right" has two particle systems and two material slots
top and bottom should be pink but top is rendered with the material of object "left".
if you hide object "left" in the viewport the right top particle system turns pink as it should.

I can't really seem to find a pattern to what is happening but I feel the material slot given in the particle system render options is not referencing the thing the UI shows as if it goes out of sync with the UI.

Also if you move the material slot (change top <-> bottom), the referenced one in the particle system->render tab also swaps which I feel should not.

Edit: it specifically happens if you have an object with multiple particle systems that use the same material. I have used that for different type of fur layers.

Possible workaround: You can kinda workaround it, if you create a separate material, duplicating it, for each particle system.

blender 2.91.0

blender-hair-particles-material.blend

I have encountered this bug with multiple objects that use multiple hair particle systems and materials. If your object has multiple material slots which the particle systems use, it goes haywire. I have this test case: - object "right" has two particle systems and two material slots - top and bottom should be pink but top is rendered with the material of object "left". - if you hide object "left" in the viewport the right top particle system turns pink as it should. I can't really seem to find a pattern to what is happening but I feel the material slot given in the particle system render options is not referencing the thing the UI shows as if it goes out of sync with the UI. Also if you move the material slot (change top <-> bottom), the referenced one in the particle system->render tab also swaps which I feel should not. Edit: it specifically happens if you have an object with multiple particle systems that use the same material. I have used that for different type of fur layers. **Possible workaround**: You can kinda workaround it, if you create a separate material, duplicating it, for each particle system. blender 2.91.0 [blender-hair-particles-material.blend](https://archive.blender.org/developer/F9531829/blender-hair-particles-material.blend)

Germano Cavalcante commented

2021-02-26 18:06:49 +01:00

Added subscriber: @SachaGoedegebure