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Hydra Prim Schemas

Hydra schemas are constantly evolving. The following list of schemas is a snapshot from November 2023.

Prim: the flattening scene index will produce these attributes on all prims in the scene.

  • xform (HdXformSchema)
  • visibility (HdVisibilitySchema)
    • visibility (bool)
  • purpose (HdPurposeSchema)
  • extent (HdExtentSchema)

Gprim: all prims for which HdPrimTypeIsGprim(type) is true optionally have these.

  • displayStyle (HdLegacyDisplayStyleSchema)
    • refineLevel (int)
    • flatShadingEnabled (bool)
    • displacementEnabled (bool)
    • occludedSelectionShowsThrough (bool)
    • pointsShadingEnabled (bool)
    • materialIsFinal (bool)
    • shadingStyle (TfToken)
    • reprSelector (VtArray<TfToken>)
    • cullStyle (TfToken)
  • instancedBy (HdInstancedBySchema)
    • paths (VtArray<SdfPath>)
    • prototypeRoots (VtArray<SdfPath>)
  • coordSysBinding (HdCoordSysBindingSchema)
    • <name> (SdfPath) - representing the path of the coordSys prim bound to <name>
  • categories (HdCategoriesSchema)
    • <name> (bool) - representing whether the prim is included or excluded from category <name>
  • primvars (HdPrimvarsSchema)
    • <name> (HdPrimvarSchema) - primvar data for <name>
      • primvarValue (HdSampledDataSource) - flattened primvar data, one value per topological primvar element.
      • indexedPrimvarValue (HdSampledDataSource) - for indexed primvars, de-duplicated primvar data, arbitrary size
      • indices (VtArray<int>) - for indexed primvars, indices into indexedPrimvarValue, one value per topological primvar element.
      • interpolation (Token)
      • role (Token)
  • materialBindings (HdMaterialBindingsSchema)
    • <name> (HdMaterialBindingSchema) - material binding for purpose <name>

Mesh

  • mesh - HdMeshSchema
    • topology (HdMeshTopologySchema)
      • faceVertexCounts (VtArray<int>)
      • faceVertexIndices (VtArray<int>)
      • holeIndices (VtArray<int>)
      • Orientation (TfToken)
    • subdivisionScheme (TfToken)
    • subdivisionTags (HdSubdivisionTagsSchema) - optional based on subdivisionScheme
      • faceVaryingLinearInterpolation (TfToken)
      • interpolateBoundary (TfToken)
      • triangleSubdivisionRule (TfToken)
      • cornerIndices (VtArray<int>)
      • cornerSharpnesses (VtArray<float>)
      • creaseIndices (VtArray<int>)
      • creaseLengths (VtArray<int>)
      • creaseSharpnesses (VtArray<float>)
    • geomSubsets (HdGeomSubsetsSchema)
      • <name> (HdGeomSubsetSchema) - geom subset with identifier <name>
        • type (TfToken) - typeFaceSet, typeCurveSet, typePointSet
        • indices (VtArray<int>)
        • Optional - visibility (bool)
        • Optional - <name> (HdMaterialBindingSchema) - material binding for purpose <name>
    • doubleSided (bool)
  • primvars (HdPrimvarsSchema)
    • points (HdPrimvarSchema) - required to have interpolation "vertex"

Basis Curves

  • basisCurves - HdBasisCurvesSchema
    • topology (HdBasisCurvesTopologySchema)
      • curveVertexCounts (VtArray<int>)
      • curveIndices (VtArray<int>)
      • basis (TfToken)
      • type (TfToken)
      • wrap (TfToken)
    • geomSubsets (HdGeomSubsetsSchema)
  • primvars (HdPrimvarsSchema)
    • points (HdPrimvarSchema) - required to have interpolation "vertex"

Volume

  • volumeFieldBindings (HdVolumeFieldBindingsSchema)
    • <name> (SdfPath) - volume field to bind to input <name>

VolumeField

  • volumeField (HdVolumeFieldSchema)
    • filePath (SdfAssetPath) - library agnostic but OpenUSD ships with OpenVDB and Field3D support.
    • fieldName (TfToken)
    • fieldIndex (int)
    • fieldDataType (TfToken)
    • vectorDataRoleHint (TfToken)

Material

  • material (HdMaterialSchema)
  • primvars (HdPrimvarsSchema)

Light

  • material (HdMaterialSchema) - we expect a "light" terminal
  • light (HdLightSchema)
    • isLight (bool)
    • materialSyncMode
    • filters (SdfPathVector)
    • lightLink (TfToken)
    • shadowLink (TfToken)
    • lightFilterLink (TfToken)
  • primvars (HdPrimvarsSchema)
  • instancedBy (HdInstancedBySchema)

Camera

  • camera (HdCameraSchema)
    • projection (TfToken)
    • horizontalAperture (float)
    • verticalAperture (float)
    • horizontalApertureOffset (float)
    • verticalApertureOffset (float)
    • focalLength (float)
    • clippingRange (GfVec2f)
    • clippingPlanes (VtArray<GfVec4d>)
    • fStop (float)
    • focusDistance (float)
    • shutterOpen (double)
    • shutterClose (double)
    • exposure (float)
    • focusOn (float)
    • dofAspect (float)
    • splitDiopter (HdSplitDiopterSchema)
      • count (int)
      • angle (float)
      • offset1 (float)
      • width1 (float)
      • focusDistance1 (float)
      • offset2 (float)
      • width2 (float)
      • focusDistance2 (float)
    • lensDistortion (HdLensDistortionSchema)
      • type (TfToken)
      • k1 (float)
      • k2 (float)
      • center (GfVec2f)
      • anaSq (float)
      • asym (GfVec2f)
      • scale (float)
      • ior (float)
  • primvars (HdPrimvarsSchema)

Instancer

  • instancerTopology - HdInstancerTopologySchema
    • prototypes (VtArray<SdfPath>)
    • instanceIndices(HdVectorDataSource)
      • <index> (HdInstanceIndicesSchema)
        • instancer (SdfPath)
        • prototypeIndex (int)
        • instanceIndices (VtArray<int>)
    • mask (VtArray<bool>)
    • instanceLocations (VtArray<SdfPath>)
  • instancedBy (HdInstancedBySchema)
  • primvars (HdPrimvarsSchema)

RenderBuffer

  • renderBuffer - HdRenderBufferSchema
    • dimensions (GfVec3i)
    • format (HdFormat)
    • multiSampled (bool)

RenderSettings