New glTF Extensions for 3D Asset Visual Realism

By Tiera Oliver

Associate Editor

Embedded Computing Design

July 16, 2021


New glTF Extensions for 3D Asset Visual Realism

The Khronos Group announced the public release of the latest set of Physically Based Rendering (PBR) material extensions for the Khronos glTF 3D asset format. The new extensions enable material properties such as refraction, color attenuation, and volumetric properties to be used by diverse renderers from real-time rasterization to production-class path-tracing.

glTF is a flexible, royalty-free asset format from Khronos designed for efficient run-time transmission and loading of 3D scenes and models on a variety of platforms including web browsers, mobile devices, PC desktops, and the cloud. Per the company, tendering engines such as Babylon.js, Google's Filament, and three.js already support some or all of the new PBR extensions, together with applications including Adobe's Substance 3D Stager, Dassault Systèmes 3DEXPERIENCE Platform, DGG RapidCompact, and UX3D's Gestaltor.

Physically Based Rendering creates realistic results by modeling the physical properties of real-world objects. It enables developers and artists to create photorealistic 3D assets by controlling parameters that correspond to the physical properties of actual materials. The three new extensions build on and extend the existing glTF 2.0 PBR capabilities by adding refraction, volume-based absorption, and complex specular reflections.

  • KHR_materials_ior: Index of Refraction describes how light is scattered as it passes through an object. By enabling artists to control IOR values, a range of transparent materials can be made to look more realistic, including air, water, eyes, glass, sapphire, and diamond.
  • KHR_materials_volume: The volume extension enables mesh surfaces to act as an interface between volumes and to enable more realistic refraction and absorption properties as seen in transparent materials. This extension gives translucent materials the appearance of depth and heft. For real-time engines incapable of ray-tracing, this extension also supplies a thickness texture map, to enable suitable approximations of light interacting with a volume of material.
  • KHR_materials_specular: Specular properties are an object's mirror-like properties: its ability to reflect light regularly, creating coherent reflections of other objects. Unlike its predecessor KHR_materials_pbrSpecularGlossiness, this new specular extension operates within the modern metallic/roughness workflow at the core of glTF's PBR material model, enabling colored specular highlights compatible across the array of advanced PBR material extensions.

According to the company, these extensions allow a wider range of scenes and objects to be represented realistically as 3D assets.

The newly ratified PBR extensions are already fully supported by the Khronos glTF Sample Viewer, UX3D's Gestaltor, and by Babylon.js.

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Tiera Oliver, Associate Editor for Embedded Computing Design, is responsible for web content edits, product news, and constructing stories. She also assists with newsletter updates as well as contributing and editing content for ECD podcasts and the ECD YouTube channel. Before working at ECD, Tiera graduated from Northern Arizona University where she received her B.S. in journalism and political science and worked as a news reporter for the university’s student led newspaper, The Lumberjack.

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