Hi,
I added three materials with different material ID to the source mesh objects. If I disable/enable “use Items Mtl IDs” than I get the same output. Did I misunderstood the feature?
-Micha
Hello @Micha ,
To achieve the result you want you need to make your Reference Object a single mesh (or polysurface) and first apply different materials to the separate faces so that V-Ray can generate Face material IDs for the faces you need. Then you need to apply a Material with a Multi-Sub texture in the Diffuse slot to the Enmesh base surface and set “Get ID from” to “Use Face Material ID”.
You can check this simple example below - I’ve created three Torus geometries and joined them into a single Polysurface with BooleanUnion. Then ctrl shift selected the separate Torus surfaces and applied to them different Materials (so that the Face material IDs are generated for the faces).
The Torus polysurface is my Reference object and a simple surface is my Enmesh base object. The material assigned to the Enmesh is a Generic material with a Multi-Sub Texture:
Unfortunately there is currently no way to find out which Face material ID has a specific face because Rhino enumerates the faces in its own order. The issue has been discussed internally, but no final decision is made yet. We will let you know if there is any progress on this matter.
Kind regards,
Iva
Thank you @iva_mancheva , I got it working like at your example. 
Is there a way to direct use different materials, like wood and metal rings? Or ist the Multi-Sub Texture the only way?
How you can apply Mat ID to the individual faces in a poly surface ?
Per Rhino sub-surface selection (Ctrl+Shift) you apply different V-Ray materials with different Mat ID to the selected sub surfaces.
Hello @Micha ,
You need a single material for the Enmesh asset, so the only way to keep multiple materials for the pattern objects is to use a Multi Material for the Enmesh geometry.
I illustrated it with the same example - the pattern object is a single polysurface, with Ctrl + Shift + Select I applied a different material to each Torus surface, then I slotted the materials in one Multi Material and applied it to the Enmesh:
As a side note - with Multi-Sub texture you can take advantage of the Randomization options and randomly change the texture on each Enmesh Instance. You can check the examples in the Docs page - V-Ray for Rhino .
Kind regards,
Iva
Thank you for the further details. The Docs examples are great.