Particle color from instancer not right in render when "Use Modifier Stack" box is checked (Cycles) #85218

New Issue

Donald L. Drennan · 2021-01-30T03:29:53+01:00

Donald L. Drennan commented

2021-01-30 03:29:53 +01:00

System Information
Operating system: Windows-7-6.1.7601-SP1 64 Bits
Graphics card: GeForce GT 710/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.75

Blender Version
Broken: version: 2.91.2, branch: master, commit date: 2021-01-19 16:15, hash: 5be9ef4177
Worked: (newest version of Blender that worked as expected)

Short description of error
Particle color inherited from instancer is disabled if there is a subdivision surface modifier above the particle modifier, and the "Use Modifier Stack" box is checked in the particle settings under the Source drop down.
Unchecking the box, or moving the particle modifier to the top fixes the problem.

Exact steps for others to reproduce the error

Download the attached project file
Enable Rendered viewport shading. Notice that the particles are colored properly
Select the Plane, switch to the Modifier Properties
Enable the subdivision modifier for the viewport and render. The particles placement should transform correctly, but the color is now black.

#85218.blend

Original instructions

Make plane, assign plane an image texture material, add subdivision surface modifier, add particle system, add a cube, assign cube to be the particles, give cube the same image in it's own material using the UV map from instancer. Particle cubes should now be the color from the spawning point of the instancer.
In the particle settings under Source check the "Use Modifier Stack" box. Put the subdivision surface modifier at the top of the stack. Particles will now turn gray in the render. In the Blend file I was working on, they showed the correct color, but the render color was gray. When I uncheck the "Use Modifier Stack" box, it renders correctly. In my test file, the render preview also shows gray particles. I'm not sure what the difference is. I'm including both Blend files.

Particle test.blend

Bauble Test.blend
Render preview window

Actual render

Thanks! this took awhile to figure out. I think this is an actual bug, because I can see no reason this should cause this error.

**System Information** Operating system: Windows-7-6.1.7601-SP1 64 Bits Graphics card: GeForce GT 710/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.75 **Blender Version** Broken: version: 2.91.2, branch: master, commit date: 2021-01-19 16:15, hash: `5be9ef4177` Worked: (newest version of Blender that worked as expected) **Short description of error** Particle color inherited from instancer is disabled if there is a subdivision surface modifier above the particle modifier, and the "Use Modifier Stack" box is checked in the particle settings under the Source drop down. Unchecking the box, or moving the particle modifier to the top fixes the problem. **Exact steps for others to reproduce the error** - Download the attached project file - Enable *Rendered* viewport shading. Notice that the particles are colored properly - Select the *Plane*, switch to the *Modifier Properties* - Enable the subdivision modifier for the viewport and render. The particles placement should transform correctly, but the color is now black. [#85218.blend](https://archive.blender.org/developer/F9605145/T85218.blend) ---- Original instructions Make plane, assign plane an image texture material, add subdivision surface modifier, add particle system, add a cube, assign cube to be the particles, give cube the same image in it's own material using the UV map from instancer. Particle cubes should now be the color from the spawning point of the instancer. In the particle settings under Source check the "Use Modifier Stack" box. Put the subdivision surface modifier at the top of the stack. Particles will now turn gray in the render. In the Blend file I was working on, they showed the correct color, but the render color was gray. When I uncheck the "Use Modifier Stack" box, it renders correctly. In my test file, the render preview also shows gray particles. I'm not sure what the difference is. I'm including both Blend files. ![Screenshot 2021-01-29 19.31.47.png](https://archive.blender.org/developer/F9604698/Screenshot_2021-01-29_19.31.47.png) [Particle test.blend](https://archive.blender.org/developer/F9604700/Particle_test.blend) [Bauble Test.blend](https://archive.blender.org/developer/F9604701/Bauble_Test.blend) Render preview window ![Screenshot 2021-01-26 17.20.48.png](https://archive.blender.org/developer/F9604713/Screenshot_2021-01-26_17.20.48.png) ![test-1-28-21-2.jpg](https://archive.blender.org/developer/F9604711/test-1-28-21-2.jpg) Actual render Thanks! this took awhile to figure out. I think this is an actual bug, because I can see no reason this should cause this error.

Donald L. Drennan commented

2021-01-30 03:29:53 +01:00

Added subscriber: @Spaceboy64

Robert Guetzkow commented

2021-01-30 11:25:13 +01:00

Added subscriber: @rjg

Robert Guetzkow commented

2021-01-30 11:25:13 +01:00

This does seem to be incorrect. I will try to simplify the example to see where at what part this is going wrong, but this might be an issue in the particle system code that is considered to be at its end of life and planned to be replaced.

Robert Guetzkow commented

2021-01-30 12:00:47 +01:00

It seems that Use Modifier Stack results in the correct placement of the particles but the UV Map is wrong when From Instancer is enabled.

In the project below the texture emit-control is used in the hair particle system to control the density (see Texture Influence ). The cube is used as render object for the particle system. It has a material which uses the UV map of the instancer and uses this to sample the color from the texture color.

#85218.blend

It seems that *Use Modifier Stack* results in the correct placement of the particles but the UV Map is wrong when *From Instancer* is enabled. In the project below the texture `emit-control` is used in the hair particle system to control the density (see [Texture Influence ](https://docs.blender.org/manual/en/latest/physics/particles/texture_influence.html)). The cube is used as render object for the particle system. It has a material which uses the UV map of the instancer and uses this to sample the color from the texture `color`. [#85218.blend](https://archive.blender.org/developer/F9605145/T85218.blend)

Robert Guetzkow commented

2021-01-30 12:06:24 +01:00

This may be the same issues as reported in #57922.

Robert Guetzkow commented

2021-01-30 12:10:16 +01:00

Closed as duplicate of #57922

Robert Guetzkow closed this issue

2021-01-30 12:10:16 +01:00

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Particle color from instancer not right in render when "Use Modifier Stack" box is checked (Cycles) #85218