New glTF Extensions Raise Bar on 3D Asset Visual Realism
July 13, 2021

New glTF Extensions Raise Bar on 3D Asset Visual Realism

BEAVERTON, OR – The Khronos Group, an open consortium of industry-leading companies creating advanced interoperability standards, has 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 wide variety of platforms including web browsers, mobile devices, PC desktops and the cloud. Leading rendering 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 Dimension, Dassault Systèmes 3DEXPERIENCE Platform, DGG RapidCompact and UX3D’s Gestaltor. 
“These enhancements to glTF’s PBR model raise the bar for material compatibility between ray-traced, path-traced, and real-time rendering implementations. They enable more realistic assets including volumetric effects, while remaining inclusive of real-time engines and viewers,” says Ed Mackey of Analytical Graphics and 3D Formats PBR task sub group chair.
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 diverse 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 fast 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. 

These extensions allow a wider range of scenes and objects to be represented realistically as 3D assets. For example, they enable artists to create more beautifully lit virtual photoshoots of products for e-commerce.
The newly ratified PBR extensions are already fully supported by the Khronos glTF Sample Viewer, UX3D’s Gestaltor and by Babylon.js. 

Khronos’ glTF (GL Transmission Format) is a royalty-free specification for the efficient transmission and loading of 3D scenes and models by engines and applications in diverse markets such as e-commerce, geospatial, virtual and augmented reality, visualization, education, design and more. glTF defines an extensible publishing format that streamlines authoring workflows and interactive services by enabling the interoperable use of 3D content across the industry. glTF minimizes the size of 3D assets and the runtime processing needed to unpack and use them. As a result, glTF assets are efficient enough to be rendered not just on high-end workstations and supercomputers, but also on mobile phones and web browsers.

Industry momentum for glTF continues to grow with pervasive support among tools and repositories for developing and distributing glTF assets - and engines, applications, and retailers using those glTF models. The Khronos 3D Formats and 3D Commerce Working Groups are actively evolving glTF, and encourage input and feedback from implementers, engine developers, content creators, artists and e-commerce companies. Any companies that wish to participate directly in evolving the glTF specification and ecosystem are warmly invited to join the Khronos Group. 

3D glTF model of olives under a glass dome using  the IOR, Specular, Transmission and Volume PBR  extensions to add reflection and refraction to  translucent materials.  Rendered in  real - time in the  Babylon.js Sandbox. Model copyright 2021 Wayfair LLC, CC by 4.0.