The Khronos Group Announces PBR Material Extensions For glTF

The team introduced new physically based rendering extensions for Clear Coat, Transmission, and Sheen.

Today, The Khronos Group launched a new set of Physically Based Rendering (PBR) material extensions for glTF. glTF is Khronos’ royalty-free format for widespread, efficient transmission and loading of 3D scenes and models, also known as the 'JPEG of 3D'. New extensions for Clear Coat, Transmission and Sheen build on the existing PBR capabilities of glTF 2.0 form a powerful, interoperable, physically-based material model for the glTF ecosystem.

Existing core glTF 2.0 PBR materials allow users to define parameters for Base Color, Metalness, Roughness, Emission, Normal Map, and Baked Ambient Occlusion. This system forms a simple to implement PBR model for high-quality, visually realistic 3D assets that are portable to any rendering API and viewer. The model is also scalable to suit the capabilities of diverse platforms including mobile devices. "By defining rendering parameters based on physical properties, instead of using model-supplied shader code, viewing engines and applications are able to implement and optimize their own rendering shaders while preserving visual consistency," noted the team.

The Khronos 3D Formats Working Group announced they're now expanding glTF’s core PBR capabilities by releasing material parameters in glTF extensions for Clear Coat, Transmission, and Sheen.

  • The KHR_materials_clearcoat extension adds a layer of shine and polish. It is a critical graphical element for the automotive industry, for example, to showcase realistic paint finishes without breaking the laws of energy conservation which can create an unnatural shine.
  • The KHR_materials_transmission extension models light passing through a material, preserving specular reflections that would be visible on a shiny transmissive surface to provide a physically-correct approximation of materials such as glass, stained glass, water, and clear or partially colored plastic. This extension uses 'Roughness' from the base glTF PBR model to blur the transmission. In this first version, thin-walled transmission is directly supported, and the extension has been designed to be compatible with future material properties that may provide a thick volumetric material definition.
  • The KHR_materials_sheen extension provides sheen roughness and sheen color channels to simulate the effect light has when it hits microfibers in cloth. This is key for artists working on apparel, furniture, or other items made of cloth or fuzzy materials.

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