Vray Displacement Modifier seems to destroy vertex color on vray proxy brought in from houdini.

[cavedog]

Hi folks,

I'm working in Max 2024 with a fairly recent version of Vray. I have an animated alembic file loaded into the Vray proxy. The alembic has 2 single channel attributes on the points that I want to use as masks for a Vray blend material. The vertex color/ houdini attribute shows up fine in the VFB until I add the Vray displacement modifier. Then it just goes black. Also, not sure if it matters but alembic has no uvs. My plan is to do everything with procedurals and triplanar. Any help would be greatly appreciated.

Best, Chris

[hermit.crab]

Try this:
1. Rather than setting a texture in the VRayDisplacementMod, activate the "Use object material"
2. Place the Displacement tex in the .abc's shader

If the .abc consists of particles, I am uncertain that this should work in the first place. Otherwise, could you attach the alembic so we can troubleshoot?

[cavedog]

Thank you HC,

l have tried what you suggested above. The vertex color disappears regardless, even if there's no displacement texture applied in the modifier. As soon as the vray displace mod is added the color goes away. If I disable the modifier it returns. I have it working using Max's alembic import and Max's default displacement. The alembic is a meshed vdb/sdf animation. It's pretty big so I've attached a file with just 1 frame and I cut it in half to make it smaller. In addition, I've changed the extension to .txt since it says I can't upload files with .abc extension. Please rename it to .abc when you download. And to be clear, the problem occurs when I import the alembic as a vray proxy and add the vray displacement modifier.

Best,
Chris

[cavedog]

I forgot to mention, the mesh currently has a 3 channel Cd attribute that I'm using as a mask. For testing you can just apply it to the diffuse color channel. All 3 channels are identical. It's a grayscale mask.

[hermit.crab]

Thanks for the provided file. Turns out we already have this issue logged (internal bug-tracker id: VMAX-14263). I've added your case to the log. For now, either use the 3ds Max alembic loader or bake the Vertex Colors and use them as a regular texture.

[cavedog]

Thanks for the heads up HC. At least now I know it's not user error.