COLLADA

This page covers how to integrate COLLADA into your metadata through namespaces.

About COLLADA

COLLADA (COLLAborative Design Activity) is an open standard digital asset exchange schema for interactive 3D applications, managed by the Khronos Group. It defines an XML-based schema to make it easy to transport 3D assets between applications without loss of information, enabling diverse 3D authoring and processing tools to be combined into a content production pipeline.

COLLADA serves as an interchange format rather than a delivery format, making it valuable in asset creation workflows before conversion to runtime formats like glTF or FBX.

Core COLLADA Concepts

Key concepts in COLLADA that are relevant to metadata integration:

• XML Schema: XML-based format with a standardized schema
• Asset Information: Metadata about the asset including contributor information
• Visual Scenes: Hierarchical arrangement of nodes
• Geometries: Mesh data with vertices, normals, and textures
• Materials and Effects: Material properties and rendering information
• Animation: Keyframe-based animation data for transformations
• Physics: Physical properties and collision information
• Kinematics: Joint hierarchies and constraints for character animation

Implementing the COLLADA Standard

Namespace Declaration

{
  "@context": {
    "@vocab": "https://schema.org/",
    "mvmd": "https://mvmd.org/v1/",
    "collada": "https://www.khronos.org/collada/schemas/"
  }
}

Linking Example

When referencing external COLLADA assets:

{
  "@context": {
    "@vocab": "https://schema.org/"
  },
  "@type": "3DModel",
  "name": "Architectural Model",
  "contentUrl": "https://example.com/models/building.dae",
  "encodingFormat": "model/vnd.collada+xml"
}

With version information:

{
  "@context": {
    "@vocab": "https://schema.org/"
  },
  "@type": "3DModel",
  "name": "Architectural Model",
  "contentUrl": "https://example.com/models/building.dae",
  "encodingFormat": "model/vnd.collada+xml",
  "version": "1.5.0",
  "contentSize": "4.3 MB"
}

Embedding Example

When embedding COLLADA metadata directly:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "collada": "https://www.khronos.org/collada/schemas/"
  },
  "@type": "3DModel",
  "name": "Architectural Model",
  "collada:version": "1.5.0",
  "collada:asset": {
    "created": "2023-08-22T14:32:25Z",
    "modified": "2023-09-15T10:45:12Z",
    "upAxis": "Y_UP",
    "unitName": "meters",
    "unitMeter": 1.0
  },
  "collada:contributors": [
    {
      "author": "Architecture Studio",
      "authoringTool": "3D Modeling Suite 2023",
      "comments": "Final version for client approval"
    }
  ],
  "collada:scenes": {
    "instanceVisualScene": "MainScene",
    "nodeCount": 156
  },
  "collada:geometries": [
    {
      "id": "Building_Exterior",
      "primitiveCount": 2450,
      "vertexCount": 4280
    },
    {
      "id": "Interior_Details",
      "primitiveCount": 3200,
      "vertexCount": 5600
    },
    {
      "id": "Landscape",
      "primitiveCount": 1200,
      "vertexCount": 2400
    }
  ]
}

Common Use Cases

COLLADA is used in a variety of applications:

• Digital content creation workflows
• 3D asset exchange between software packages
• Architectural visualization
• Game development assets
• Film and animation production
• Cultural heritage preservation
• CAD/CAM model exchange

Implementation Examples

Basic Example

A simple COLLADA model reference:

{
  "@context": {
    "@vocab": "https://schema.org/"
  },
  "@type": "3DModel",
  "name": "Historical Building",
  "description": "Detailed model of a historical building with architectural features",
  "contentUrl": "https://example.com/models/historical-building.dae",
  "encodingFormat": "model/vnd.collada+xml",
  "license": "https://creativecommons.org/licenses/by/4.0/"
}

Complete Example

For a complete model with detailed metadata:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "collada": "https://www.khronos.org/collada/schemas/"
  },
  "@type": "3DModel",
  "name": "Historic City Center",
  "description": "Detailed architectural model of a historic city center with multiple buildings and landscape elements",
  "contentUrl": "https://example.com/models/historic-city.dae",
  "encodingFormat": "model/vnd.collada+xml",
  "creator": {
    "@type": "Organization",
    "name": "Digital Heritage Foundation",
    "url": "https://dhf.example.org"
  },
  "license": "https://creativecommons.org/licenses/by-nc/4.0/",
  "dateCreated": "2023-06-28",
  "collada:version": "1.5.0",
  "collada:asset": {
    "created": "2023-06-28T09:15:42Z",
    "modified": "2023-07-15T14:22:36Z",
    "upAxis": "Y_UP",
    "unitName": "meters",
    "unitMeter": 1.0,
    "title": "Historic City Center Reconstruction",
    "subject": "Architectural heritage, Urban planning, 17th century"
  },
  "collada:contributors": [
    {
      "author": "Historical Research Team",
      "authoringTool": "Architectural Modeling Suite 4.5",
      "comments": "Based on historical documents and archaeological surveys"
    },
    {
      "author": "Texture Artists Group",
      "authoringTool": "Texture Creation Suite 2023",
      "comments": "Period-accurate textures with weathering effects"
    }
  ],
  "collada:library": {
    "visualScenes": ["MainScene", "AerialView", "StreetLevel"],
    "lights": ["Sunlight", "AmbientLight", "StreetLamps"],
    "cameras": ["MainCamera", "TourCamera", "DetailCamera"],
    "effects": 24,
    "materials": 36,
    "geometries": 85,
    "images": 42
  },
  "collada:extraInfo": {
    "accuracy": "High - based on archaeological evidence",
    "restorationNotes": "Missing elements were reconstructed based on similar structures from the same period",
    "historyBrief": "This area was constructed between 1650-1680 and represents the baroque style of the region",
    "references": ["City Archives Document #A-456-78", "Historical Society Publication Vol.23"]
  }
}

Cultural Heritage Example

Example for cultural heritage documentation:

{
  "@context": {
    "@vocab": "https://schema.org/",
    "mvmd": "https://mvmd.org/v1/",
    "collada": "https://www.khronos.org/collada/schemas/"
  },
  "@type": "3DModel",
  "name": "Ancient Temple Reconstruction",
  "description": "Digital reconstruction of the Temple of Apollo based on archaeological evidence",
  "contentUrl": "https://heritage.example.org/models/apollo-temple.dae",
  "encodingFormat": "model/vnd.collada+xml",
  "creator": {
    "@type": "Organization",
    "name": "Archaeological Digital Preservation Institute",
    "url": "https://adpi.example.org"
  },
  "license": "https://creativecommons.org/licenses/by-nc-sa/4.0/",
  "dateCreated": "2023-04-12",
  "additionalProperty": [
    {
      "@type": "PropertyValue",
      "propertyID": "heritageMetadata",
      "name": "Heritage Metadata",
      "value": {
        "historicalPeriod": "Classical Greek",
        "approximateDate": "447-438 BCE",
        "location": {
          "name": "Athens, Greece",
          "coordinates": [37.9715, 23.7268]
        },
        "preservationStatus": "Partially preserved",
        "excavationReferences": [
          "Athens Archaeological Survey 1982",
          "Classical Architecture Database ID: GR-AT-438"
        ],
        "uncertainty": {
          "architectural": "Low - based on extensive remains",
          "decorative": "Medium - based on fragments and comparable sites",
          "colorScheme": "High - speculative based on traces and contemporary accounts"
        }
      }
    }
  ],
  "collada:version": "1.5.0",
  "collada:asset": {
    "upAxis": "Y_UP",
    "unitName": "meters",
    "unitMeter": 1.0
  },
  "collada:library": {
    "visualScenes": ["CompleteView", "ExteriorOnly", "InteriorOnly", "StructuralElements"],
    "geometries": 146,
    "materials": 28
  }
}

JSON Schema Validation

For validating COLLADA namespace references in MVMD, the following schema properties are defined:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "COLLADA Namespace Schema",
  "type": "object",
  "properties": {
    "collada:version": {
      "type": "string",
      "description": "COLLADA schema version"
    },
    "collada:asset": {
      "type": "object",
      "description": "Core asset information",
      "properties": {
        "created": {
          "type": "string",
          "format": "date-time",
          "description": "Creation date of the asset"
        },
        "modified": {
          "type": "string",
          "format": "date-time",
          "description": "Last modification date"
        },
        "upAxis": {
          "type": "string",
          "enum": ["X_UP", "Y_UP", "Z_UP"],
          "description": "Up-axis of the coordinate system"
        },
        "unitName": {
          "type": "string",
          "description": "Name of the length unit"
        },
        "unitMeter": {
          "type": "number",
          "description": "Conversion factor to meters"
        },
        "title": {
          "type": "string",
          "description": "Title of the asset"
        },
        "subject": {
          "type": "string",
          "description": "Subject or keywords"
        }
      }
    },
    "collada:contributors": {
      "type": "array",
      "description": "Information about the contributors",
      "items": {
        "type": "object",
        "properties": {
          "author": { "type": "string" },
          "authoringTool": { "type": "string" },
          "comments": { "type": "string" }
        }
      }
    },
    "collada:scenes": {
      "type": "object",
      "description": "Scene information"
    },
    "collada:geometries": {
      "type": "array",
      "description": "Geometry information",
      "items": {
        "type": "object",
        "properties": {
          "id": { "type": "string" },
          "primitiveCount": { "type": "integer" },
          "vertexCount": { "type": "integer" }
        }
      }
    },
    "collada:library": {
      "type": "object",
      "description": "Information about the COLLADA libraries used"
    },
    "collada:extraInfo": {
      "type": "object",
      "description": "Additional custom information"
    }
  }
}

JSON-LD Context

The COLLADA namespace can be mapped to JSON-LD context for semantic interoperability:

{
  "@context": {
    "collada": "https://www.khronos.org/collada/schemas/",
    "collada:version": { "@id": "collada:version" },
    "collada:asset": { "@id": "collada:asset" },
    "collada:contributors": { "@id": "collada:contributors" },
    "collada:scenes": { "@id": "collada:scenes" },
    "collada:geometries": { "@id": "collada:geometries" },
    "collada:library": { "@id": "collada:library" },
    "collada:extraInfo": { "@id": "collada:extraInfo" }
  }
}

Implementation Considerations

When implementing the COLLADA namespace, keep these considerations in mind:

• Interchange Format: COLLADA is primarily an interchange format, not an optimized runtime format
• Version Compatibility: Be explicit about which COLLADA version you're using (1.4.1, 1.5.0)
• File Size: COLLADA files can be large due to the XML structure, consider compression
• Validation: Validate against the official schema to ensure compatibility
• Conversion Pipeline: Often used in pipelines that ultimately convert to more optimized formats
• External References: Properly handle external references to textures and other resources
• Complex Features: Some advanced features like physics may not translate to all target platforms

Related Documentation

• Cross-Platform Asset Implementation
• glTF Standard
• FBX Namespace
• Asset Implementation