- 1. Foreword
- 2. Introduction
- 3. Object Model Basics
- 4. Core Pointers
- 5. Extension Pointers
- 5.1. KHR_texture_transform
- 5.2. KHR_lights_punctual
- 5.3. KHR_materials_anisotropy
- 5.4. KHR_materials_clearcoat
- 5.5. KHR_materials_dispersion
- 5.6. KHR_materials_emissive_strength
- 5.7. KHR_materials_ior
- 5.8. KHR_materials_iridescence
- 5.9. KHR_materials_sheen
- 5.10. KHR_materials_specular
- 5.11. KHR_materials_transmission
- 5.12. KHR_materials_volume
- 5.13. EXT_lights_ies
- 5.14. EXT_lights_image_based
- 5.15. ADOBE_materials_clearcoat_specular
- 5.16. ADOBE_materials_clearcoat_tint
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Note
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Note
Khronos posts the AsciiDoc source of the glTF specification to enable community feedback and remixing under CC-BY 4.0. Published versions of the Specification are located in the glTF Registry. |
Copyright 2023 The Khronos Group Inc.
This Document is protected by copyright laws and contains material proprietary to Khronos. Except as described by these terms, it or any components may not be reproduced, republished, distributed, transmitted, displayed, broadcast or otherwise exploited in any manner without the express prior written permission of Khronos.
Khronos grants a conditional copyright license to use and reproduce the unmodified Document for any purpose, without fee or royalty, EXCEPT no licenses to any patent, trademark or other intellectual property rights are granted under these terms.
Khronos makes no, and expressly disclaims any, representations or warranties, express or implied, regarding this Document, including, without limitation: merchantability, fitness for a particular purpose, non-infringement of any intellectual property, correctness, accuracy, completeness, timeliness, and reliability. Under no circumstances will Khronos, or any of its Promoters, Contributors or Members, or their respective partners, officers, directors, employees, agents or representatives be liable for any damages, whether direct, indirect, special or consequential damages for lost revenues, lost profits, or otherwise, arising from or in connection with these materials.
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This document, referred to as the “glTF 2.0 Asset Object Model Specification” or just the “Object Model” hereafter, describes a portable runtime object model of a glTF asset.
The following documents are referenced by normative sections of the specification:
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glTF 2.0 Specification https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html
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Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed., JavaScript Object Notation (JSON) Pointer, RFC 6901, DOI 10.17487/RFC6901, April 2013, https://www.rfc-editor.org/info/rfc6901
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ISO/IEC 60559 Floating-point arithmetic https://www.iso.org/standard/80985.html
Although glTF 2.0 Specification does not define any runtime behavior, there is a growing demand for manipulating glTF assets at runtime and querying their state in a portable way.
Upon loading, applications usually parse glTF JSON into implementation-specific internal structures and therefore do not have a common protocol to manipulate asset contents.
This document defines a set of JSON pointers that glTF implementations are expected to support for identifying asset properties that could be manipulated at runtime.
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The Object Model is defined only for valid glTF assets. Querying or setting properties of invalid glTF assets are undefined.
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Upon loading an asset, an implementation registers specific glTF object properties for the Object Model by resolving JSON pointers identified by templates provided by this document to JSON properties of the asset being loaded. Undefined glTF properties that have schema-default values are considered defined with their default values.
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Each instance of empty curly braces (
{}) in the pointer templates is replaced with the corresponding array element index for each glTF asset property matching the template. -
Since JSON does not natively support vectors and matrices, the Object Model defines explicit types for all supported properties. JSON pointers to properties of these types are resolved into implementation-specific vectors and matrices, not raw JSON arrays. Pointers to individual vector or matrix components are not resolved.
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Pointers to properties of explicit array types (as defined below) are resolved to implementation-defined arrays; pointers to array elements of properties of explicit array types are resolved to the corresponding array elements.
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In addition to properties directly linked to glTF JSON, the Object Model defines extra read-only properties that reflect commonly-used parts of the glTF runtime state. Specifically, array sizes and current node transforms.
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If a JSON pointer cannot be resolved to a glTF property, operations with it are undefined.
The following data types are assumed by this document:
- float
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single or double precision IEEE-754 floating-point type
- float[]
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an array of float values
- float2
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a two-component vector of float values read from or set to JSON array elements with indices 0 and 1
- float3
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a three-component vector of float values read from or set to JSON array elements with indices 0, 1, and 2
- float4
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a four-component vector of float values read from or set to JSON array elements with indices 0, 1, 2, and 3
- float4x4
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a 4x4 matrix of float values
- int
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a signed integer type with width of at least 32 bits
The following pointer templates represent mutable properties defined in the core glTF 2.0 Specification.
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As in the core glTF 2.0 Specification, lengths of the |
Additionally, the following pointer templates represent read-only runtime properties.
| Pointer | Type | Comment |
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Number of animations |
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Number of cameras |
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Number of materials |
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Number of meshes |
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Number of morph targets |
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Number of nodes |
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Local transformation matrix of a node |
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Global transformation matrix of a node |
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Number of the associated mesh’s morph targets; undefined if the node has no mesh |
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Number of scenes |
The following pointer templates represent mutable properties defined in glTF 2.0 extensions.
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By definition, this extension applies to all properties of textureInfo type, including texture properties defined in other glTF 2.0 extensions.
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Additional read-only properties
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Number of punctual lights |
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Additional read-only properties
| Pointer | Type | Comment |
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Number of IES light profiles |
| Pointer | Type |
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Additional read-only properties
| Pointer | Type | Comment |
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Number of image-based lights |
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