Geometry

Generated from the schema registry by ernie schema --markdown.

Imageable

What every prim has: visibility, purpose and the world it is in.

Abstract base

Attribute	Type	Description	Fallback	Values	Source
visibility	token	"invisible" hides the prim and its descendants.	"inherited"	inherited, invisible	UsdGeom
purpose	token	Which renders include it and its descendants: default, render, proxy or guide.	"default"	default, render, proxy, guide	UsdGeom
ernie:world	int	The batch world the prim and its descendants are in; -1 for every world.	-1	≥ -1	Ernie

Xformable

What has a transform, composed from its xformOps.

Abstract base · Inherits Imageable

Attribute	Type	Description	Fallback	Values	Source
xformOpOrder	token[]	The xformOp attributes composing the local transform, outermost first.	[]		UsdGeom

Boundable

What has an extent in its own space, computed from its attributes.

Abstract base · Inherits Xformable

Attribute	Type	Description	Fallback	Values	Source
extent	float[]	Authored local bounds (min x, y, z, max x, y, z), read until the geometry is available.	[]		UsdGeom

Gprim

Geometry, drawn in a display colour or with a bound material.

Abstract base · Inherits Boundable

Attribute	Type	Description	Fallback	Values	Source
primvars:displayColor	color3d	Linear RGB of the whole prim.	[0.5,0.5,0.5]	≥ 0	UsdGeom
primvars:displayOpacity	double	Opacity of the whole prim.	1.0	≥ 0, ≤ 1	UsdGeom
doubleSided	bool	Whether its back faces are seen too.	false		UsdGeom
orientation	token	The winding of its front faces.	"rightHanded"	rightHanded, leftHanded	UsdGeom

Xform

A transform grouping its children.

Prim type · Inherits Xformable

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Xform": {
      "typeName": "Xform"
    }
  }
}

Scope

A grouping without a transform of its own.

Prim type · Inherits Imageable

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Scope": {
      "typeName": "Scope"
    }
  }
}

GeomModelAPI

A model's stand-ins and the bounds hint used while its subtree isn't loaded.

API schema

Attribute	Type	Description	Fallback	Values	Source
model:drawMode	token	Draws the subtree as itself, or as a stand-in: its origin axes, its bounds or cards.	"inherited"	origin, bounds, cards, default, inherited	UsdGeom
model:applyDrawMode	bool	Whether this prim's draw mode replaces its subtree.	false		UsdGeom
model:drawModeColor	color3d	Linear RGB of the stand-in.	[0.18,0.18,0.18]	≥ 0	UsdGeom
model:cardGeometry	token	Cards through the centre, on the bounds' faces, or as the textures place them.	"cross"	cross, box, fromTexture	UsdGeom
model:cardVisibility	token	Every textured card, or only one per axis.	"inherited"	full, simple, inherited	UsdGeom
model:cardTextureXPos	asset	The image on the card facing this way.	""		UsdGeom
model:cardTextureYPos	asset	The image on the card facing this way.	""		UsdGeom
model:cardTextureZPos	asset	The image on the card facing this way.	""		UsdGeom
model:cardTextureXNeg	asset	The image on the card facing this way.	""		UsdGeom
model:cardTextureYNeg	asset	The image on the card facing this way.	""		UsdGeom
model:cardTextureZNeg	asset	The image on the card facing this way.	""		UsdGeom
extentsHint	float[]	The subtree's local bounds per purpose (default, render, proxy, guide), six floats each, read while it isn't loaded.	[]		UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/GeomModelAPI": {
      "typeName": "Xform",
      "apiSchemas": ["GeomModelAPI"],
      "model:drawMode": "inherited",
      "model:applyDrawMode": false,
      "model:drawModeColor": [0.18, 0.18, 0.18],
      "model:cardGeometry": "cross",
      "model:cardVisibility": "inherited",
      "extentsHint": []
    }
  }
}

GeomSubset

Some faces, points, edges, segments or tetrahedra of its parent, to bind a material to or select.

Prim type

Attribute	Type	Description	Fallback	Values	Source
elementType	token	What its indices count.	"face"	face, point, edge, segment, tetrahedron	UsdGeom
indices	int[]	The elements in the subset.			UsdGeom
familyName	token	The family of subsets it is one of, as materialBind for per-face materials.	""		UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/GeomSubset": {
      "typeName": "GeomSubset",
      "elementType": "face"
    }
  }
}

Cube

A box centred on its origin, size along each axis.

Prim type · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
size	double	Edge length, metres.	2.0	≥ 0	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Cube": {
      "typeName": "Cube",
      "size": 2.0
    }
  }
}

Sphere

A sphere centred on its origin.

Prim type · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
radius	double	Metres.	1.0	≥ 0	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Sphere": {
      "typeName": "Sphere",
      "radius": 1.0
    }
  }
}

Cylinder

A capped cylinder along its axis.

Prim type · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
radius	double	Metres.	1.0	≥ 0	UsdGeom
height	double	Metres along the axis.	2.0	≥ 0	UsdGeom
axis	token	The axis of its height, or a plane's normal.	"Z"	X, Y, Z	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Cylinder": {
      "typeName": "Cylinder",
      "radius": 1.0,
      "height": 2.0,
      "axis": "Z"
    }
  }
}

Cone

A capped cone along its axis, its apex at +height / 2.

Prim type · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
radius	double	Metres.	1.0	≥ 0	UsdGeom
height	double	Metres along the axis.	2.0	≥ 0	UsdGeom
axis	token	The axis of its height, or a plane's normal.	"Z"	X, Y, Z	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Cone": {
      "typeName": "Cone",
      "radius": 1.0,
      "height": 2.0,
      "axis": "Z"
    }
  }
}

Capsule

A cylinder with hemispherical caps along its axis.

Prim type · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
radius	double	Metres, of the cylinder and its end caps.	0.5	≥ 0	UsdGeom
height	double	Metres along the axis between the caps.	1.0	≥ 0	UsdGeom
axis	token	The axis of its height, or a plane's normal.	"Z"	X, Y, Z	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Capsule": {
      "typeName": "Capsule",
      "radius": 0.5,
      "height": 1.0,
      "axis": "Z"
    }
  }
}

Plane

A one-sided rectangle facing along its axis.

Prim type · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
width	double	Metres along x, or z when the axis is X.	2.0	≥ 0	UsdGeom
length	double	Metres along y, or z when the axis is Y.	2.0	≥ 0	UsdGeom
axis	token	The axis of its height, or a plane's normal.	"Z"	X, Y, Z	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Plane": {
      "typeName": "Plane",
      "width": 2.0,
      "length": 2.0,
      "axis": "Z"
    }
  }
}

PointBased

Geometry from an array of points.

Abstract base · Inherits Gprim

Attribute	Type	Description	Fallback	Values	Source
points	float[n, 3]	float32 or float64 (n, 3) positions in its own space.			UsdGeom
velocities	float[n, 3]	(n, 3) metres per second of each point.			UsdGeom
accelerations	float[n, 3]	(n, 3) metres per second squared.			UsdGeom
normals	float[n, 3]	(n, 3) normals; computed from the faces when unset.			UsdGeom

Mesh

A polygon mesh, or the control mesh of a subdivision surface.

Prim type · Inherits PointBased

Attribute	Type	Description	Fallback	Values	Source
faceVertexCounts	int[]	The number of vertices of each face.			UsdGeom
faceVertexIndices	int[]	The point indices of the faces' vertices, in order.			UsdGeom
subdivisionScheme	token	The surface the faces are the control mesh of; none draws the faces themselves.	"catmullClark"	catmullClark, loop, bilinear, none	UsdGeom
interpolateBoundary	token	How boundary edges and corners are interpolated.	"edgeAndCorner"	none, edgeOnly, edgeAndCorner	UsdGeom
faceVaryingLinearInterpolation	token	Where face-varying primvars stay linear rather than smoothed.	"cornersPlus1"	none, cornersOnly, cornersPlus1, cornersPlus2, boundaries, all	UsdGeom
triangleSubdivisionRule	token	Catmull-Clark's weights for triangles, or smoother ones.	"catmullClark"	catmullClark, smooth	UsdGeom
holeIndices	int[]	Faces left out of the surface.			UsdGeom
cornerIndices	int[]	Points that are sharp corners.			UsdGeom
cornerSharpnesses	float[]	The sharpness of each corner.			UsdGeom
creaseIndices	int[]	Point indices of creases, one after another.			UsdGeom
creaseLengths	int[]	The number of points of each crease.			UsdGeom
creaseSharpnesses	float[]	The sharpness of each crease, or of each crease edge.			UsdGeom
ernie:subdivision:refineLevel	int	Uniform refinement of the surface: 2^level segments along each control edge.	1	≥ 0, ≤ 8	Ernie

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Mesh": {
      "typeName": "Mesh",
      "subdivisionScheme": "catmullClark",
      "interpolateBoundary": "edgeAndCorner",
      "faceVaryingLinearInterpolation": "cornersPlus1",
      "triangleSubdivisionRule": "catmullClark",
      "ernie:subdivision:refineLevel": 1
    }
  }
}

Points

A point cloud of spheres, each its own width.

Prim type · Inherits PointBased

Attribute	Type	Description	Fallback	Values	Source
widths	float[]	Diameters in metres: one per point, or one for all.			UsdGeom
ids	int[]	int64 ids that follow points across time samples.			UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/Points": {
      "typeName": "Points"
    }
  }
}

Curves

Batched curves, each a run of points, swept by its widths.

Abstract base · Inherits PointBased

Attribute	Type	Description	Fallback	Values	Source
curveVertexCounts	int[]	The number of points of each curve.			UsdGeom
widths	float[]	Diameters in metres: per point, per segment end, or one for all.			UsdGeom

BasisCurves

Linear or cubic curves: hair, fur, cables and wires.

Prim type · Inherits Curves

Attribute	Type	Description	Fallback	Values	Source
type	token	Linear segments, or cubic ones by the basis.	"cubic"	linear, cubic	UsdGeom
basis	token	The cubic basis.	"bezier"	bezier, bspline, catmullRom	UsdGeom
wrap	token	Open curves, closed ones, or open ones through their end points.	"nonperiodic"	nonperiodic, periodic, pinned	UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/BasisCurves": {
      "typeName": "BasisCurves",
      "type": "cubic",
      "basis": "bezier",
      "wrap": "nonperiodic"
    }
  }
}

NurbsCurves

Rational B-spline curves of any order.

Prim type · Inherits Curves

Attribute	Type	Description	Fallback	Values	Source
order	int[]	The order (degree + 1) of each curve.			UsdGeom
knots	float[]	Each curve's knots, curveVertexCount + order of them.			UsdGeom
ranges	float[n, 2]	(n, 2) parametric range drawn of each curve.			UsdGeom
pointWeights	float[]	Rational weights, one per point.			UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/NurbsCurves": {
      "typeName": "NurbsCurves"
    }
  }
}

HermiteCurves

Cubic curves through their points with a tangent at each.

Prim type · Inherits Curves

Attribute	Type	Description	Fallback	Values	Source
tangents	float[n, 3]	(n, 3) tangent of each point.			UsdGeom

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/HermiteCurves": {
      "typeName": "HermiteCurves"
    }
  }
}

PointInstancer

Prototypes placed at instances, bounded by their bounds at each instance.

Prim type · Inherits Boundable

Attribute	Type	Description	Fallback	Values	Source
prototypes	rel[]	The prims instanced, indexed by the proto indices.	[]		UsdGeom
protoIndices	int[]	The prototype of each instance.			UsdGeom
positions	float[n, 3]	(n, 3) positions in the instancer's space; the number of instances.			UsdGeom
orientations	float[n, 4]	(n, 4) rotations as quaternions.			UsdGeom
scales	float[n, 3]	(n, 3) scales.			UsdGeom
velocities	float[n, 3]	(n, 3) metres per second.			UsdGeom
accelerations	float[n, 3]	(n, 3) metres per second squared.			UsdGeom
angularVelocities	float[n, 3]	(n, 3) degrees per second.			UsdGeom
ids	int[]	int64 ids that follow instances across time samples.			UsdGeom
invisibleIds	int[]	The ids of instances to hide.			UsdGeom
ernie:quaternionOrder	token	The component order of the orientations: xyzw (USD, Warp, PhysX) or wxyz (Isaac Lab, MuJoCo).	"xyzw"	xyzw, wxyz	Ernie
ernie:worlds	int[]	int (n,): each instance's world.			Ernie

{
  "$schema": "https://alexmaietta.github.io/ernie/schema/ernie-scene.schema.json",
  "prims": {
    "/World/PointInstancer": {
      "typeName": "PointInstancer",
      "ernie:quaternionOrder": "xyzw"
    }
  }
}