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The V-Ray Material Instance Asset is a material asset which enables you to easily create V-Ray materials in Unreal. For more details see the V-Ray Material Instance Asset documentation.

Render material from .vrscene

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This feature enables you to switch between rendering the material that was set in Unreal Engine or the material that was stored in the vrscene file. This gives the possibility to use various and more complex materials that were created outside Unreal but still render ( e.g. Blend materials, Carpaints, Subsurface materials, etc.). For more details see the Render material from.vrscene documentation.

External Material Libraries

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If you would like to use a material that is not yet supported, you can take advantage of the functionality to map, by name, Unreal materials to V-Ray materials created with another V-Ray plugin (e.g. V-Ray for Maya, V-Ray for 3ds Max, etc.). In order for this to work, the materials have to be exported as a vrscene file (this would be the EML file). The mapping works by matching the name of a material in Unreal, against the name of a material in the EML file. In addition, the materials in the  EML file need to have a scene_name parameter set. It will be the name to match against a material in Unreal. For more details see the External Material Libraries documentation.