NVIDIA's Material Definition Language (MDL) provides the ability to share physically based materials across different applications. If you build a library of MDL materials, they can be used in other programs that also support MDL data. V-Ray provides a material that allows .mdl files to be loaded, which includes the shading properties.
Most vMaterials work with VRayMDLMtl, but there's an environment variable that you need to set. To the environment variable VRAY_MDL_PATH_3DSMAXNNNN_x64 (where NNNN is the 3ds Max version), add the paths to the vMaterials MDL sources. For example:
C:\ProgramData\NVIDIA Corporation\mdl;C:\Users\<username>\Documents\mdl;C:\Program Files\Chaos Group\V-Ray\3dsmax 2017 for x64\mdl
where <username> is the name of the Windows user account. You can set environment variables from Control Panel > System > Advanced system settings > Environment variables.
Reloading the same MDL module is not possible because of some limitations of the NVIDIA's SDK that we use to provide MDL support. This feature will probably appear at some point, but for now, the only way to achieve this is by renaming the MDL file.
MDL Materials exported from Substance Designer are supported. You can read more about how to import the materials on the 3ds Max Rendering MDL Textures page.
Diffuse transmission is not supported for the moment.
The following features are unsupported or ignored in V-Ray MDL.
- material_emission.mode is ignored
- material.backface is ignored
- diffuse_transmission_bsdf is not supported
- backscattering_glossy_reflection_bsdf is not supported
- measured_bsdf is not supported
- from the "alternative distribution functions", only the microfacet_ggx_smith_bsdf is implemented
- measured_edf and spot_edf are not supported
- anisotropic_vdf is not supported
- 3d textures also don't work yet
- material.volume is ignored in V-Ray for GPU
- UTF-8 resource file paths are not supported