VRayDisplacementMod doesn't work with material IDs?

[Alex_M]

I'm trying to add displacement to some parts of my object. I'm using Multi/sub-object material where only one of the materials has displacement and a VRayDisplacementMod is applied to the object with "Use object material" turned on. However, displacement gets applied to the whole object. Is this supposed to happen?

[ChuckRT]

Not really, even without VrayDisplacement Mod, displacement its only applied to the part where has it (while with modifier you need to activate "use object material" just like you said).
Could you share your material and modifier setup?

"use object material" in Displacement Mod

Displacement on Material

No "use object material" on Displacement Mod

[Alex_M]

Thanks, ChuckRT. I found what the problem was! The "Shift" parameter of the VRayDisplacementMod modifier shifts the whole objects, not just the materials with displacement. If I set Shift to 0, things look correct. Unfortunately, the displaced geometry now expands too much and I can't shift it back to it's original place as this will shift the whole object. Is there a way to shift it in the material?

[hermit.crab]

Thanks for the report. I've logged it (internal bug-tracker id: VMAX-14014). Not sure if there is a way to do this without detaching the face.

[Joelaff]

What if you shift via subtracting a VRayColor from your map?

Be sure the texture high and low settings cover your range (e.g. -1 to 1 ).

So if your original image is 0-1.0 then subtract 0.5 via VrayCompTex and a VrayColor.

Note I did not test this just now, and there may be some other gotcha.

[Alex_M]

Good idea! I will try it out and report the results.