draft of EXT_materials_dispersion

extensions/2.0/Vendor/EXT_materials_dispersion/README.md

@@ -0,0 +1,121 @@
+# EXT\_materials\_disperson
+
+## Contributors
+
+- Ben Houston, Threekit [@bhouston](https://github.com/bhouston)
+
+Copyright 2023 The Khronos Group Inc. All Rights Reserved. glTF is a trademark of The Khronos Group Inc.
+See [Appendix](#appendix-full-khronos-copyright-statement) for full Khronos Copyright Statement.
+
+## Status
+
+Draft
+
+## Dependencies
+
+Written against the glTF 2.0 spec.
+
+## Exclusions
+
+- This extension must not be used on a material that also uses `KHR_materials_pbrSpecularGlossiness`.
+- This extension must not be used on a material that also uses `KHR_materials_unlit`.
+
+## Overview
+
+This extension adds one parameters to the metallic-roughness material: `dispersion`.
+
+`disperson` allows users to configure the strength of the dispersion effect in terms of its Abby number. The dispersion effect is a result of the wavelength-dependent index of refraction of a material. It is also known as chromatic aberration.
+
+## Extending Materials
+
+The dispersion, defined in terms of Abby number, is defined by adding the `KHR_materials_dispersion` extension to any glTF material.
+
+```json
+{
+    "materials": [
+        {
+            "extensions": {
+                "EXT_materials_dispersion": {
+                    "dispersion": 42
+                }
+            }
+        }
+    ]
+}
+```
+
+Factor and texture are combined by multiplication to describe a single value.
+
+| |Type|Description|Required|
+|-|----|-----------|--------|
+| **dispersion** | `number` | The strength of the dispersion effect, specified as an Abby number. | No, default: `59`|
+
+The default value of 59 is taken from the low dispersion of crown glass.
+
+## Implementation
+
+*This section is non-normative.*
+
+*TODO*
+
+## Interaction with other extensions
+
+*TODO*
+
+
+## Schema
+
+- [material.KHR_materials_dispersion.schema.json](schema/material.KHR_materials_dispersion.schema.json)
+
+## Appendix: Full Khronos Copyright Statement
+
+Copyright 2023 The Khronos Group Inc.
+
+Some parts of this Specification are purely informative and do not define requirements
+necessary for compliance and so are outside the Scope of this Specification. These
+parts of the Specification are marked as being non-normative, or identified as
+**Implementation Notes**.
+
+Where this Specification includes normative references to external documents, only the
+specifically identified sections and functionality of those external documents are in
+Scope. Requirements defined by external documents not created by Khronos may contain
+contributions from non-members of Khronos not covered by the Khronos Intellectual
+Property Rights Policy.
+
+This specification 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.
+
+This specification has been created under the Khronos Intellectual Property Rights
+Policy, which is Attachment A of the Khronos Group Membership Agreement available at
+www.khronos.org/files/member_agreement.pdf. Khronos grants a conditional
+copyright license to use and reproduce the unmodified specification for any purpose,
+without fee or royalty, EXCEPT no licenses to any patent, trademark or other
+intellectual property rights are granted under these terms. Parties desiring to
+implement the specification and make use of Khronos trademarks in relation to that
+implementation, and receive reciprocal patent license protection under the Khronos
+IP Policy must become Adopters and confirm the implementation as conformant under
+the process defined by Khronos for this specification;
+see https://www.khronos.org/adopters.
+
+Khronos makes no, and expressly disclaims any, representations or warranties,
+express or implied, regarding this specification, 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.
+
+Vulkan is a registered trademark and Khronos, OpenXR, SPIR, SPIR-V, SYCL, WebGL,
+WebCL, OpenVX, OpenVG, EGL, COLLADA, glTF, NNEF, OpenKODE, OpenKCAM, StreamInput,
+OpenWF, OpenSL ES, OpenMAX, OpenMAX AL, OpenMAX IL, OpenMAX DL, OpenML and DevU are
+trademarks of The Khronos Group Inc. ASTC is a trademark of ARM Holdings PLC,
+OpenCL is a trademark of Apple Inc. and OpenGL and OpenML are registered trademarks
+and the OpenGL ES and OpenGL SC logos are trademarks of Silicon Graphics
+International used under license by Khronos. All other product names, trademarks,
+and/or company names are used solely for identification and belong to their
+respective owners.

extensions/2.0/Vendor/EXT_materials_dispersion/schema/material.KHR_materials_dispersion.schema.json

@@ -0,0 +1,19 @@
+{
+    "$schema": "http://json-schema.org/draft-04/schema",
+    "title": "KHR_materials_dispersion glTF Material Extension",
+    "type": "object",
+    "description": "glTF extension that defines the strength of dispersion.",
+    "allOf": [ { "$ref": "glTFProperty.schema.json" } ],
+    "properties": {
+        "dispersion": {
+            "type": "number",
+            "description": "The strength of the dispersion.",
+            "default": 59.0,
+            "minimum": 1.0,
+            "maximum": 1000.0,
+            "gltf_detailedDescription": "This parameter defines dispersion in terms of the Abby number formulation."
+        },
+        "extensions": { },
+        "extras": { }
+    }
+}