FRAUNHOFER_external_model extension

extensions/2.0/Vendor/FRAUNHOFER_external_model/README.md

@@ -0,0 +1,113 @@
+# FRAUNHOFER_external_model
+
+## Contributors
+
+* Johannes Behr, Threedy GmbH, [@jbehr](https://github.com/jbehr)
+* Timo Sturm, Threedy GmbH, [@tsturm](https://github.com/tsturm)
+* Manuel Olbrich, Fraunhofer IGD [@dschie](https://github.com/dschie)
+
+## Status
+
+Fraunhofer Vendor Extension - Currently supported by [X3DOM](https://github.com/x3dom/x3dom) 1.8.0+ and [instant3Dhub](https://www.threedy.io/) 3.0.0+.
+
+## Dependencies
+
+Written against the glTF 2.0 spec.
+
+## Overview
+
+State representation containing domain related payload and links to further resources are the key concept of data on the web. The abstract RFC2077 [1] definition for the “model/\*” domain include 3D objects as payload and links inside the “model/\*” domain. Some registered standards (e.g. X3D) include links to other 3D-Models as base concepts. 
+
+Those links allow a natural distribution of 3d data into more than one resource which support different change rates, reuse and logical packaging. 
+
+Unfortunately referencing external models is not provided by the current glTF Specification. With our FRAUNHOFER_external_model extension we want to propose a simple way to support this.
+
+Client implementations of the FRAUNHOFER_external_model extension must support at least one glTF format but can support and negotiate any number of glTF and non-glTF encodings as long as those follow
+* the abstract model definition RFC2077 [1],
+* provide a registered content type (e.g. model/gltf+json) [2]
+* and can be determinate with some form of content negotiation [3].
+
+Figure 1 shows a screenshot of our public available FRAUNHOFER_external_model [example](https://examples.x3dom.org/FRAUNHOFER_external_model/).
+
+<figure>
+<img src="./figures/figure0.png">
+<figcaption><em>Figure 1: A glTF with FRAUNHOFER_external_model extension loaded in X3DOM. Left: local glTF mesh. middle: external glTF model, right: external X3D model (content negotiation).</em></figcaption>
+</figure>
+
+## glTF Schema Updates
+
+The proposed extension requires only a small amount of glTF Schema Updates.
+
+### Model Storage
+
+Models are stored in the newly introduced models array of the asset.
+
+Where each model contains one of
+
+* a URI to an external file in one of the supported model formats, or
+* a URI with embedded base64-encoded data, or
+* a reference to a bufferView; in that case mimeType must be defined.
+
+The following example shows three different ways of defining a model.
+* The first model is defined as a direct link to an external glTF file.
+* The second model is also defined as a direct link to an external model file, but without any suffix. This allows the Loader to use content negotiation [3] to fetch a preffered model format.
+* The third model is defined as a reference to a bufferview which contains glTF-Binary data.
+
+```
+"models":
+[
+    {
+        "uri": "https://modeldatabase.io/primitives/box.gltf"
+    },
+    {
+        "uri": "https://modeldatabase.io/primitives/box"
+    },
+    {
+        "bufferView": 33,
+        "mimeType" : "model/gltf-binary"
+    }
+]
+```
+
+> **Implementation Note:** When model data is provided by uri and mimeType is defined, client implementations should prefer JSON-defined MIME Type over one provided by transport layer.
+
+### Model Instantiation
+
+A model is instantiated by node.model property. The same model could be used by many nodes, which could have different transformations. For example:
+
+```
+"nodes":
+[
+    {
+        "name": "Untransformed External Model",
+        "model": 0
+    },
+    {
+        "name": "Transformed External Model",
+        "model": 0,
+        "translation": [
+            20,
+            0,
+            0
+        ]  
+    }
+]
+```
+
+### JSON Schema
+
+* [glTF.schema.json](schema/glTF.schema.json)
+* [model.schema.json](schema/model.schema.json)
+* [node.schema.json](schema/node.schema.json)
+
+## Known Implementations
+
+* [X3DOM](https://github.com/x3dom/x3dom) 1.8.0+
+* [instant3Dhub](https://www.threedy.io/) 3.0.0+
+
+## Resources
+
+* [1] RFC2077. 1997. Model Primary Content Type. (1997). Retrieved Jan 28, 2018 from https://tools.ietf.org/html/rfc2077
+* [2] IANA. 2018. IANA Model Registration. (2018). Retrieved Jan 28, 2018 from https://www.iana.org/assignments/media-types/media-types.xhtml#model
+* [3] HTTP. 2018. HTTP Content Negotiation. (2018). Retrieved Jan 28, 2018 from https://www.w3.org/Protocols/rfc2616/rfc2616-sec12.html
+* [4] Johannes Behr, Max Limper, and Timo Sturm. 2018. MoST: a 3D web architectural style for hybrid model data. In Proceedings of the 23rd International ACM Conference on 3D Web Technology (Web3D '18). ACM, New York, NY, USA, Article 21, 8 pages. DOI: https://doi.org/10.1145/3208806.3208823

extensions/2.0/Vendor/FRAUNHOFER_external_model/schema/glTF.schema.json

@@ -0,0 +1,163 @@
+{
+    "$schema": "http://json-schema.org/draft-04/schema",
+    "title": "glTF",
+    "type": "object",
+    "description": "The root object for a glTF asset.",
+    "allOf": [ { "$ref": "glTFProperty.schema.json" } ],
+    "properties": {
+        "extensionsUsed": {
+            "type": "array",
+            "description": "Names of glTF extensions used somewhere in this asset.",
+            "items": {
+                "type": "string"
+            },
+            "uniqueItems": true,
+            "minItems": 1
+        },
+        "extensionsRequired": {
+            "type": "array",
+            "description": "Names of glTF extensions required to properly load this asset.",
+            "items": {
+                "type": "string"
+            },
+            "uniqueItems": true,
+            "minItems": 1
+        },
+        "accessors": {
+            "type": "array",
+            "description": "An array of accessors.",
+            "items": {
+                "$ref": "accessor.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of accessors.  An accessor is a typed view into a bufferView."
+        },
+        "animations": {
+            "type": "array",
+            "description": "An array of keyframe animations.",
+            "items": {
+                "$ref": "animation.schema.json"
+            },
+            "minItems": 1
+        },
+        "asset": {
+            "allOf": [ { "$ref": "asset.schema.json" } ],
+            "description": "Metadata about the glTF asset."
+        },
+        "buffers": {
+            "type": "array",
+            "description": "An array of buffers.",
+            "items": {
+                "$ref": "buffer.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of buffers.  A buffer points to binary geometry, animation, or skins."
+        },
+        "bufferViews": {
+            "type": "array",
+            "description": "An array of bufferViews.",
+            "items": {
+                "$ref": "bufferView.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of bufferViews.  A bufferView is a view into a buffer generally representing a subset of the buffer."
+        },
+        "cameras": {
+            "type": "array",
+            "description": "An array of cameras.",
+            "items": {
+                "$ref": "camera.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of cameras.  A camera defines a projection matrix."
+        },
+        "images": {
+            "type": "array",
+            "description": "An array of images.",
+            "items": {
+                "$ref": "image.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of images.  An image defines data used to create a texture."
+        },
+        "materials": {
+            "type": "array",
+            "description": "An array of materials.",
+            "items": {
+                "$ref": "material.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of materials.  A material defines the appearance of a primitive."
+        },
+        "meshes": {
+            "type": "array",
+            "description": "An array of meshes.",
+            "items": {
+                "$ref": "mesh.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of meshes.  A mesh is a set of primitives to be rendered."
+        },
+        "models": {
+            "type": "array",
+            "description": "An array of models.",
+            "items": {
+                "$ref": "model.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of models.  A model defines data used to create a model."
+        },
+        "nodes": {
+            "type": "array",
+            "description": "An array of nodes.",
+            "items": {
+                "$ref": "node.schema.json"
+            },
+            "minItems": 1
+        },
+        "samplers": {
+            "type": "array",
+            "description": "An array of samplers.",
+            "items": {
+                "$ref": "sampler.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of samplers.  A sampler contains properties for texture filtering and wrapping modes."
+        },
+        "scene": {
+            "allOf": [ { "$ref": "glTFid.schema.json" } ],
+            "description": "The index of the default scene."
+        },
+        "scenes": {
+            "type": "array",
+            "description": "An array of scenes.",
+            "items": {
+                "$ref": "scene.schema.json"
+            },
+            "minItems": 1
+        },
+        "skins": {
+            "type": "array",
+            "description": "An array of skins.",
+            "items": {
+                "$ref": "skin.schema.json"
+            },
+            "minItems": 1,
+            "gltf_detailedDescription": "An array of skins.  A skin is defined by joints and matrices."
+        },
+        "textures": {
+            "type": "array",
+            "description": "An array of textures.",
+            "items": {
+                "$ref": "texture.schema.json"
+            },
+            "minItems": 1
+        },
+        "extensions": { },
+        "extras": { }
+    },
+    "dependencies": {
+        "scene": [ "scenes" ]
+    },
+    "required": [ "asset" ]
+}

extensions/2.0/Vendor/FRAUNHOFER_external_model/schema/model.schema.json

@@ -0,0 +1,44 @@
+{
+    "$schema": "http://json-schema.org/draft-04/schema",
+    "title": "Model",
+    "type": "object",
+    "description": "Model data used to create a model. Model can be referenced by URI or `bufferView` index. `mimeType` is required in the latter case.",
+    "allOf": [ { "$ref": "glTFChildOfRootProperty.schema.json" } ],
+    "properties": {
+        "uri": {
+            "type": "string",
+            "description": "The uri of the model.",
+            "format": "uriref",
+            "gltf_detailedDescription": "The uri of the model.  Relative paths are relative to the .gltf file.  Instead of referencing an external file, the uri can also be a data-uri. The model format must be gltf or glb.",
+            "gltf_uriType": "image"
+        },
+        "mimeType": {
+            "anyOf": [
+                {
+                    "enum": [ "model/gltf+json" ]
+                },
+                {
+                    "enum": [ "model/gltf-binary" ]
+                },
+                {
+                    "type": "string"
+                }
+            ],
+            "description": "The models's MIME type. Required if `bufferView` is defined."
+        },
+        "bufferView": {
+            "allOf": [ { "$ref": "glTFid.schema.json" } ],
+            "description": "The index of the bufferView that contains the model. Use this instead of the model's uri property."
+        },
+        "name": { },
+        "extensions": { },
+        "extras": { }
+    },
+    "dependencies": {
+        "bufferView": [ "mimeType" ]
+    },
+    "oneOf": [
+        { "required": [ "uri" ] },
+        { "required": [ "bufferView" ] }
+    ]
+}