OE_materials_roughnessMetallicOcclusion

Table of Contents

• Contributors
• Status
• Dependencies
• Overview
• JSON Schema
• Known Implementations
• Licence

Contributors

Lautriva

Status

Stable

Dependencies

Written against the glTF 2.0 spec.

Overview

Internally, the Oxygen Engine uses the RouMetAo (Roughness, Metallic, Ambient Occlusion) texture packing in its own PBR renderer.

But by default, the glTF 2.0 uses the AoRouMet (Ambient Occlusion, Roughness, Metallic) texture packing.

This extension aim to avoid multiple processing / texture swizzling if your workflow is already using RouMetAo packing beforehand.

The extension defines a single property roughnessMetallicOcclusionTexture which takes an index to the texture which is packed in the RouMetAo order.

If both a standard glTF roughnessMetallicTexture and this extension are defined in the material, this extension will take priority. Any client that does not support this extension can safely ignore this additional packed texture and rely on the default packing of glTF 2.0

For example, here is how to use the extension on a material:

{
    "materials": [
        {
            "pbrMetallicRoughness": {
                "baseColorTexture": {
                    "index": 0
                }
            },
            "normalTexture": {
                "index": 1
            },
            "extensions": {
                "OE_materials_roughnessMetallicOcclusion": {
                    "roughnessMetallicOcclusionTexture": {
                        "index": 2
                    }
                }
            }
        }
    ],
    "textures": [
        {
            "name": "baseColorTexture",
            "source": 0,
        },
        {
            "name": "normalTexture",
            "source": 1
        },
        {
            "name": "roughnessMetallicOcclusionTexture",
            "source": 2
        }
    ],
    "images": [
        {
            "mimeType": "image/png",
            "bufferView": 0
        },
        {
            "mimeType": "image/png",
            "bufferView": 1
        },
        {
            "mimeType": "image/png",
            "bufferView": 2
        }
    ]
}

JSON Schema

{
  "$schema": "http://json-schema.org/draft-04/schema",
  "title": "OE_materials_roughnessMetallicOcclusion extension",
  "type": "object",
  "description": "glTF extension that specifies a different packing order for roughness, metallic and occlusion properties in a single texture.",
  "allOf": [ { "$ref": "glTFProperty.schema.json" } ],
  "properties": {
    "roughnessMetallicOcclusionTexture": {
      "type": "object",
      "description": "A texture with packing Roughness (R), Metallic (G), Occlusion (B).",
      "properties": {
        "index": {
          "allOf": [ { "$ref": "glTFid.schema.json" } ],
          "description": "The index of the texture."
        }
      }
    },
    "extensions": {},
    "extras": {}
  }
}

Known Implementations

Only implemented in Oxygen Engine so far

Licence

MIT