[KHR_materials_clearcoat](https://github.com/KhronosGroup/glTF/blob/master/extensions/2.0/Khronos/KHR_materials_clearcoat/README.md) [KHR_materials_sheen](https://github.com/KhronosGroup/glTF/blob/master/extensions/2.0/Khronos/KHR_materials_sheen/README.md) [KHR_materials_transmission](https://github.com/KhronosGroup/glTF/blob/master/extensions/2.0/Khronos/KHR_materials_transmission/README.md) IOR Specular Volume EXT_mesh_gpu_instancing Are all of these properties supported in exporters for maya