Displacement slows down a Multi-SubObject material.

[RockinAkin]

To keep things a bit more organized for the artists down the pipe, we try to group all materials of a character under a multi-subobject material.

For parts that need displacement, we manually assign VRayDisplacementMod's to those pieces of geo - and we check the 'use object mtl'.

The problem we're encountering is when any material has a displacement map applied:

What happens is that render time rockets up as soon as a material with displacement is plugged into the main multi-subobject material.
If the displacement material is assigned directly the the object (instead of through the multi-subobject material) then render times return to normal.

Anyone else experience this or know whats happening? Is V-Ray's displacement trying to subdivide EVERYTHING else under the multi-subobject material? That's all I can think that would be causing the slowdown. Thanks!

[vlado]

Is V-Ray's displacement trying to subdivide EVERYTHING else under the multi-subobject material? That's all I can think that would be causing the slowdown. Thanks!

This is what happens, yes. We could add an option to only displace objects that have VRayDisplacementMod applied to them - would this work?

Best regards,
Vlado

[RockinAkin]

Yes - that'd be very much appreciated! Thank you Vlado!

[RockinAkin]

Just wanted to check in - any updates on this issue?
It really makes things more difficult for the character department.

[vlado]

Thanks for the reminder, will check what happened to this.

Best regards,
Vlado

[vasil.minkov]

Hello,

I tried to reproduce the problem without success. With my scene setup there was not a difference in render times between Multi/Sub-Object material and direct assignment of a displacement material. The pieces that aren't displaced rendered quite fast, regardless that they use multi/sub-object material.
Could you send us a scene that reproduces the slow down problem?

[RockinAkin]

The only files I have immediately on hand are client files - so I'll need to whip something else up give you an example file.

Will keep you posted - thanks Vasil!