Khronos glTF Extension Design Principles

The Khronos Group evaluates new extensions for glTF through a defined set of philosophical principles designed to balance continuous graphical innovation with format stability. Because glTF is positioned as the standard runtime asset delivery format—often called the "JPEG of 3D"—any proposed extension must undergo rigorous scrutiny regarding runtime efficiency, cross-platform interoperability, implementation consensus, and backward compatibility before it is ratified.

Transmission and Runtime Efficiency Over Authoring Completeness

glTF is fundamentally an asset delivery format, not a digital content creation (DCC) or authoring format. When evaluating extensions, the Khronos 3D Formats Working Group rejects proposals that introduce complex dependency graphs, parametric curves, or procedural generation that requires heavy CPU-side preprocessing. Data structures within an extension must be laid out for direct transmission into modern GPU APIs (such as Vulkan, WebGPU, Metal, and DirectX) with minimal parsing, memory allocation, or runtime overhead.

Graceful Degradation and Compatibility

Extensions must not unnecessarily break renderers that lack support for them. Khronos requires extension authors to declare whether an extension is strictly required (extensionsRequired) or merely optional (extensionsUsed). Where possible, extensions are expected to provide fallback properties using baseline glTF 2.0 definitions. For instance, advanced material extensions (such as clearcoat, sheen, or transmission) build additively on top of the standard Metallic-Roughness Physically Based Rendering (PBR) model, allowing basic renderers to still display an aesthetically coherent asset.

Multi-Vendor Consensus and Independence

To prevent proprietary lock-in and fragmentation, Khronos does not ratify core or multi-vendor (KHR_ or EXT_) extensions without broad industry consensus. An extension must be proven across multiple independent engines, authoring tools, and platforms before graduating. The evaluation process demands proof that at least two independent implementations (both export and import/render) can parse and display the feature identically, ensuring that specifications reflect practical reality rather than theoretical design.

Strict Standardization of Visual and Physical Models

Extensions that introduce new visual capabilities must adhere to well-defined physical or mathematical models rather than arbitrary shader code. By standardizing explicit physical parameters—such as index of refraction, volumetric attenuation, or dispersion—the working group ensures that an asset rendered in a web browser using WebGL appears visually identical when loaded in a native desktop game engine or an enterprise visualization suite.

Minimalism and Modularity

The core glTF specification is kept intentionally minimal, with new features isolated into modular extensions. Khronos favors small, orthogonal extensions that can be combined cleanly rather than monolithic additions that introduce cross-feature dependencies. This modular approach allows resource-constrained environments, such as mobile or embedded AR applications, to implement only the subset of extensions relevant to their performance budgets without carrying unused specification bloat.