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If you wish to import a mesh through a VRayProxy node, the mesh must first be exported to a .vrmesh file. See the V-Ray Proxy Export page for details.
If you want to edit an imported geometry, add an Unpack SOP first and set the Preview Type of the VRayProxy to Full Geometry.
The .vrmesh File Format
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Meshes are exported to a special .vrmesh file format. It contains all geometric information for a mesh – vertices and face topology as well as texture channels, face material IDs, smoothing groups, normals – in short, everything that is needed to render the mesh. In addition, the mesh is preprocessed and subdivided into chunks for easier access. The file also contains a simplified version of the mesh used for preview purposes in the viewports.
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