Version 1.0.00
Last Updated: December 8, 2021
This work is licensed under a CC BY 4.0 license.
This document is (c) 2021, Khronos Group. Usage and license details are at the end of the document.
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- Recommendations for KHR_xmp_json_ld usage in glTF
- Overview
- Model 3D namespace
- Recommended XMP Fields for 3D Models
- Sample 3D models
- Supporting Tooling and Viewers
- Copyright Header
This document outlines recommended XMP fields for use with 3D models primarily using glTF and the KHR_xmp_json_ld extension. While all XMP standardized fields, such as Dublin Core, are usable with 3D models, the goal of this document is to align the industry on some important fields to allow tooling and viewers a subset of XMP fields which can be depended on. Additionally, this document specifies the model3d XMP namespace which contains fields specific to 3D models.
While this document does primarily focus on glTF and the KHR_xmp extension, the authors' hope is to provide basic guidelines for XMP usage within other 3D formats as well.
The model3d namespace provides properties relevant to 3D models not found in other namespaces.
The namespace URI is https://schema.khronos.org/model3d/xsd/1.0/
| Field Name | Description | Type |
|---|---|---|
| model3d:spdxLicense | Contains the standardized identifier defined in the SPDX license list for this resource. The intent of this field is to provide a machine-readable identification of the content license. | Text |
| model3d:preferredSurfaces | An array of strings to indicate the preferred surfaces that an object rests on or attach to. The intent is to provide hints for AR viewers about the ideal locations for object placement without being prescriptive or restricting placement on other surface types. Direction terms like “up” and “down” in the following fields refer to the surface normal of the plane or anchor point in the world.Current standardized values are:
This string is left open for custom values, but it is recommeded that the standardized values are used |
Array of Text |
In addition to the model3d namespace, there are a number of exisiting fields in definied XMP namespaces to help identify and describe the contents of a 3D model. The following list contains suggested fields that users adopt:
| Field Name | Description | Type |
|---|---|---|
| dc:creator | Creator of the model | Array of ProperName |
| dc:description | Description of the model | Language Alternative |
| dc:language | Language of the content in this model. This represents the languages used in the geometry and texture maps of the model | Array of Locale |
| dc:rights | Human readable license field to compliment the SPDX entry | Language Alternative |
| dc:title | Title of the model | Language Alternative |
| xmp:CreateDate | Original creation date of model | Date |
| xmp:MetadataDate | Date of last update to metadata | Date |
| xmp:ModifyDate | Date of last update to model contents | Date |
| xmpRights:Owner | Identifies the IP owner of the 3D asset | Array of ProperName |
| xmpRights:UsageRights | Instructions on how a resource can be legally used | Language Alternative |
| xmpRights:Marked | Indicates if an asset is a rights managed or within the public domain. When true, the asset is managed by copyright, trademark or other marking. When false, the asset is in the public domain. | Boolean |
The following is example metadata that could be used for the glTF “Damaged Sci-fi Helmet” sample model.
| Fields Used in Example |
|---|
| dc:description |
| dc:rights |
| dc:title |
| dc:relation |
| model3d:spdxLicense |
{
"packets": [
{
"@context": {
"dc": "http://purl.org/dc/elements/1.1/",
"rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
"model3d": "https://schema.khronos.org/model3d/xsd/1.0/"
},
"@id": "",
"dc:description": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "The original model was built on an early draft of glTF 2.0 that did not become final. This new model has been imported and re-exported from Blender to bring it into alignment with the final release glTF 2.0 specification."
}
},
"model3d:spdxLicense": "CC-BY-NC-4.0",
"dc:relation": {
"@set": [
"https://sketchfab.com/theblueturtle_",
"https://sketchfab.com/models/b81008d513954189a063ff901f7abfe4"
]
},
"dc:rights": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "By theblueturtle_(https://sketchfab.com/theblueturtle_), published under a Creative Commons Attribution-NonCommercial license."
}
},
"dc:title": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "Battle Damaged Sci-fi Helmet - PBR"
}
}
}
]
}This example demonstrates how to include indication of the language of written text on an asset and/or metadata in multiple languages using XMP's Language Alternatives feature. Use the dc:language field to specify what language is used on the asset, not in the metadata. For metadata internationalization, use XMP's Language Alternatives.
| Fields Used in Example |
|---|
| dc:description |
| dc:language |
| dc:title |
| model3d:spdxLicense |
{
"packets": [
{
"@context": {
"dc": "http://purl.org/dc/elements/1.1/",
"rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
"model3d": "https://schema.khronos.org/model3d/xsd/1.0/"
},
"@id": "",
"dc:description": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "This is an example using language alternatives."
},
"rdf:_2": {
"@language": "de-de",
"@value": "Dies ist ein Beispiel für die Verwendung von Language Alternatives."
}
},
"model3d:spdxLicense": "CC-BY-NC-4.0",
"dc:title": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "Model with text in a texture"
}
}
}
]
}This example shows the bare minimum metadata recommended for files that are not in the public domain, and protected by copyright or other marked situations.
xmpRights:UsageTerms should be used in this situation to include legalese indicating what end-users can do with this asset. We recommend that basic copyright terms should be included within the dc:rights field.
| Fields Used in Example |
|---|
| dc:creator |
| dc:description |
| dc:title |
| dc:rights |
| xmpRights:Marked |
| xmp:MetadataDate |
| xmpRights:UsageTerms |
| xmpRights:Owner |
{
"packets": [
{
"@context": {
"dc": "http://purl.org/dc/elements/1.1/",
"rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
"xmp": "http://ns.adobe.com/xap/1.0/",
"xmpRights": "http://ns.adobe.com/xap/1.0/rights/"
},
"@id": "",
"dc:creator": {
"@list": ["Khronos 3DCommerce Working Group"]
},
"dc:description": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "Example XMP metadata demonstrating how to include All Rights Reserved metadata."
}
},
"dc:title": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "All Rights Reserved Example"
}
},
"xmp:MetadataDate": "2020-08-01T12:00Z",
"xmpRights:Marked": true,
"xmpRights:UsageTerms": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "This work is copyright 2020 by The Khronos Group, Inc. All Rights Reserved. You are not permitted to share or use this in any derivative works."
}
},
"xmpRights:Owner": "The Khronos Group, Inc."
}
]
}When using Creative Commons licensing, we recommend that creators additionally use the guidelines for specifying license information provided by Creative Commons. It is strongly advised to also include the SPDX code for the Creative Commons license you are using in the model3d:license field. This provides a machine-readable format for viewers and tooling. This example shows the bare minimum metadata recommended for files using Creative Commons licensing.
| Fields Used in Example |
|---|
| dc:creator |
| dc:description |
| dc:title |
| xmp:MetadataDate |
| xmpRights:Marked |
| xmpRights:UsageTerms |
| model3d:spdxLicense |
{
"packets": [
{
"@context": {
"dc": "http://purl.org/dc/elements/1.1/",
"rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
"xmp": "http://ns.adobe.com/xap/1.0/",
"xmpRights": "http://ns.adobe.com/xap/1.0/rights/",
"model3d": "https://schema.khronos.org/model3d/xsd/1.0/"
},
"@id": "",
"dc:creator": ["Khronos 3DCommerce Working Group"],
"dc:description": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "Example XMP metadata demonstrating how to include Creative Commons rights metadata."
}
},
"dc:title": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "Creative Commons Example"
}
},
"xmp:MetadataDate": "2020-08-01T12:00Z",
"xmpRights:Marked": false,
"xmpRights:UsageTerms": {
"@type": "rdf:Alt",
"rdf:_1": {
"@language": "en-us",
"@value": "This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License."
}
},
"model3d:spdxLicense": "CC-BY-4.0"
}
]
}Example 3D Models with XMP metadata can be found in the glTF Sample Models repository, such as the Transmission Test model.
Tools and viewers that support both writing and reading KHR_xmp metadata with glTF can be found under the metadata tag in the glTF Project Explorer.
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