MaterialX and MDL

Click the links below to access the following material libraries:

• NVIDIA vMaterials Library - A collection of realistic real-world materials described in the NVIDIA Material Definition Language (MDL) designed and verified by NVIDIA Material Specialists for accuracy, control, and consistency.
• AMD GPUOpen MaterialX Library - A downloadable library of ready-to-use PBR materials in the open-source MaterialX format.
• Physical Based database - A database of physically based values for CG artists.

For additional resources to help understand and use MDL, see NVIDIA MDL - Handbook. It provides background, theory, and practical examples of the language.

For the Precomputed Illumination mode in the OpenGL renderer and the CPU and GPU raytracers, MDL materials are processed to a simplified model, due to real time constraints. This simplified model is based on a roughness/metalness PBR model with some modifications. The MDL material gets simplified to the general metal, specular, and diffuse layers modeled with an anisotropic/isotropic GGX BRDF. On top of those layers, there is the clearcoat layer modeled with an isotropic GGX BRDF. Specular transmission is modeled using the absorption_coefficient and scattering_coefficients as combined coefficients for the Beer-Lambert Law, without changing the IOR in between boundaries (no refraction or internal reflections) for OpenGL and fully taking into account the IOR between boundaries in the raytracer's Precomputed Illumination mode. Diffuse transmission in OpenGL is approximated by a simplified diffuse lit approximation of subsurface scattering. Transparency is implemented as alpha blending. Emissions don't light the scene.

Unsupported Features

These features are not supported in the OpenGL renderer and CPU/GPU raytracers Precomputed mode:

• The bidirectional distribution functions: measured_bsdf.
• All emissive distribution functions.
• All the hair bidirectional scattering distribution functions.
• The distribution function modifiers and combiners: measured_curve_layer, thin_film, directional_factor, and measured_curve_factor.
• Resources: light profile files and BSDF measurement data files.

These features are not supported in only the OpenGL renderer:

• All volume distribution functions.

Partially Supported Features

These features are partially supported in the OpenGL renderer and CPU/GPU raytracers Precomputed mode:

• Supported BSDFs will be approximated as best as possible with microfacet_ggx_vcavities_bsdf and diffuse_reflection_bsdf.
• Supported distribution function modifiers and combiners will be used to combine the metal, specular, diffuse, transmissive, and clearcoat layers.

VRED 2025.3 now supports the MaterialX SDK 1.39.1, which supports the OpenPBR model, and the MDL SDK 2024.0.4. If using VRED 2025.1, it supports the MDL 2023.1.4 SDK and MaterialX 1.38.9, as well as CHS/JPN/KOR character sets in node, material, output, texture, or materialX filenames when exporting as a USD file.

1. Download MDL materials from the Nvidia website and MaterialX from the AMD website.
2. In the Material Editor, select > Create Material, and select either a MaterialX or MDL material.
3. Double-click a MaterialX or MDL to load the material definition into VRED. Now, you will see all available editable attributes.

Each MaterialX or MDL will have its own unique sections, such as Transmission, Sheen, Emission, or Thin Film, along with the standard ones listed below. The Attributes section contains settings from the original material definition.

Displacement

The following is a list of the parameters for changing the displacement of a material:

• Intersection Precision - Sets the precision of the displacement evaluation during raytracing. A lower value will provide a more accurate result, while a higher value will improve performance but might cause artefacts on high frequency displacement maps.

• Build Precision - Sets the precision of the displacement evaluation during acceleration structure build in raytracing. A lower value will provide a more accurate match but will slow build performance, while a higher value will improve build performance but might miss peaks, if the displacement changes rapidly, causing clamped displacement.

• Value Limit (OpenGL) - Sets the range limits for the displacement values in OpenGL. Values outside the range are clamped, causing the displacement to have flat plateaus. The range should, therefore, be large enough to cover the whole range of values but not too large as to limit performance.

• Use Accurate Silhouettes in OpenGL - Allows you to calculate the displacement in OpenGL, like in raytracing mode. Selecting it may drastically reduce the performance.

Please note, there are currently a few limitations for displacement mapping in MaterialX and MDL materials:

• Only heightmap displacement maps are supported. For vector displacement maps, only the length of the projection onto the surface normal will be used as displacement.
• Displacement is only applied in object space, at the moment. World space displacements will be treated as object space displacements.
• In OpenGL, artefacts on transparent materials can be visible. This is a known issue.

For information on standard attributes, see the following:

• Texture Settings
• Subsurface
• Incandescence
• Raytracing
• Rounded Edges
• Common