geometryBuffer.cmn.md

geometryBuffer

Mesh Geometry Description

Important: The order of the vertex attributes in the buffer is fixed to simplify binary parsing:

position
normal
uv0
uv1
color
uvRegion
featureId
faceRange

or

compressedAttributes

Important:

• Attribute that are present are store contiguously in the corresponding geometry buffers.
• All vertex attributes ( except compressedAttributes) have a fixed size that may be computed as: #component * sizeof( type ) * {#vertices or #features}

Related:

cmn::geometryDefinition

Properties

Property	Type	Description
offset	integer	The number of bytes to skip from the beginning of the binary buffer. Useful to describe 'legacy' buffer that have a header. Default=0.
position	geometryPosition	Vertex positions relative to oriented-bounding-box center.
normal	geometryNormal	Face/vertex normal.
uv0	geometryUV	First set of UV coordinates. Only applies to textured mesh.
color	geometryColor	The colors attribute.
uvRegion	geometryUVRegion	UV regions, used for repeated textures in texture atlases.
featureId	geometryFeatureID	FeatureId attribute.
faceRange	geometryFaceRange	Face range for a feature.
compressedAttributes	compressedAttributes	Compressed attributes. Cannot be combined with any other attributes.

Examples

Example: I3S v1.6 equivalent geometry buffer definition (with UV regions)

 {
  "offset": 8,
  "position": {
    "type": "Float32",
    "component": 3
  },
  "normal": {
    "type": "Float32",
    "component": 3
  },
  "uv0": {
    "type": "Float32",
    "component": 2
  },
  "color": {
    "type": "UInt8",
    "component": 4
  },
  "uvRegion": {
    "type": "UInt16",
    "component": 4
  },
  "featureId": {
    "type": "UInt64",
    "component": 1,
    "binding": "per-feature"
  },
  "faceRange": {
    "type": "UInt32",
    "component": 2,
    "binding": "per-feature"
  }
} 

Example: A compressed geometry buffer definition with featureId (without normal, with UV regions)

 {
  "compressedAttributes": {
    "encoding": "draco",
    "attributes": [
      "position",
      "uv0",
      "color",
      "feature-index",
      "uv-region"
    ]
  }
}