Materials and textures

Rhino PBR materials map to Blender's Principled BSDF channel by channel:

Non-PBR Rhino materials are read from diffuse colour, transparency, reflectivity and shine, then routed to whichever of four shader paths fits: glass, metal, emission, or standard Principled.

Per-face materials. Brep sub-object material assignments arrive as separate Blender material slots with the correct face indices, so a multi-material Brep does not need splitting.

Texture placement. Textures land where Rhino puts them. WCS and WCS box projections are rebuilt as shader nodes (the R2B Rhino Texture Projection group), measured in Rhino's model units and following the object's OCS frame when it has one. Mapping-channel textures use Rhino's own texture coordinates, including custom mappings set on the object. Each texture's repeat, offset and rotation carry over. Limitations: a mesh carries one UV set, so a material whose textures use different mapping channels places them all with the first one; quad-remeshed objects get no UVs; after moving an OCS-mapped object, Rhino's viewport can show its texture offset differently from Blender.

Texture transfer. Images are sent as binary and written to a disk cache keyed by content hash. A map shared across many materials crosses the wire once. On reconnect the add-on sends the hashes it already holds and Rhino skips those entirely.

Your own materials win. If you replace a material Rhino assigned, the sync records that the slot no longer holds what it put there and stops reclaiming it. This applies to block definitions too.