Geometry Types

polymesh

Polygonal mesh geometry. A polygonal mesh is formed of points, a vertex list (defining vertices) and start index list (defining faces). Additional information, such as normals and arbitrary data, can also be defined.

Type	Attribute	Description
float[3n]	geometry.point.N	List of per-point normals.
float[3n]	geometry.point.P	List of points. The geometry points are unique floating point positions in object space coordinates (x, y, z). Each point is only stored once but it may be indexed many times by a particular vertex.
int[]	geometry.poly.startIndex	A list of indices defining the faces of a mesh. For example, consider a cube. A cube has a startIndex list size equal to the number of faces in the mesh plus one. This is because we must store the index of the first point on the first face as well as the end point of all the faces (including the first). So, for example, the beginning of a cube’s startIndex list may look like: 0 - 0 1 - 4 2 - 8 The indices for each polygon N are from startIndex(N) to startIndex(N+1)-1. The value at index 0 of the list tells us the first face should start at index 0 in the vertexList, the second value in the list tells us the first face ends at index 3 (n-1).
int[]	geometry.poly.vertexList	Describes the vertex data of a mesh. There is a vertex at each edge intersection. The value of the vertexList is used as an index into the geometry.point.P list, which stores the actual object coordinates of each unique point. Many indices in a vertexList can index the same point in the geometry.point.P list. This saves space as a vertex is described as a simple integer rather then the three floating point values required to describe a 3D geometry point (x, y, z).
float[3n]	geometry.vertex.N	List of per-face vertex normals.
float[2n]	geometry.vertex.UV	List of texture coordinates (per vertex, non face-varying)

subdmesh

Sub-division surfaces geometry. Sub-division surfaces (Subds) are similarly structured to polygonal meshes.

Note

This section is under construction.

Type	Attribute	Description
int	geometry.facevaryinginterpolateboundary geometry.facevaryingpropagatecorners geometry.interpolateBoundary
int[]	geometry.creaseIndices
int[]	geometry.creaseLengths
float[] int[]	geometry.creaseSharpness geometry.creaseSharpnessLengths
int[]	geometry.cornerIndices
float[]	geometry.cornerSharpness
int[]	geometry.holePolyIndices
float[]	geometry.point.Pref
group	geometry.point	See polymesh.
group	geometry.poly	See polymesh.
group	geometry.vertex	See polymesh.

pointcloud

Point cloud geometry. A point cloud is the simplest form of geometry and only requires point data to be specified.

Type	Attribute	Description
group	geometry.point	See polymesh.

nurbspatch

NURBS patch geometry. NURBS patches are a special type of geometry, quite different from conventional mesh types. A NURBS curve is defined by its order, a set of weighted control points and a knot vector.

Type	Attribute	Description
int	geometry.uSize geometry.vSize	The size.
float[4n]	geometry.point.Pw	List of control points and their weights, in the order: x y z w.
int	geometry.u.order geometry.v.order	The order.
float	geometry.u.min geometry.u.max	Parameters defining the NURBS patch.
float[]	geometry.u.knots geometry.v.knots	Knot vector, a sequence of parameter values.
group	geometry.trimcurves	Parameters defining the NURBS patch.

curves

For creating groups of curves parented to the same transform. Curves cannot be created by the UI but can be created through the Python API.

The following XML is from a scene graph that creates 3 linear curves with 3 segments:

<attr type="GroupAttr" inheritChildren="false">
  <attr type="IntAttr" name="degree" tupleSize="1">
    <sample value="1 " size="1" time="0"/>
  </attr>
  <attr type="FloatAttr" name="knots" tupleSize="1">
    <sample value="0.0 " size="1" time="0"/>
  </attr>
  <attr type="IntAttr" name="numVertices" tupleSize="1">
    <sample value="4 4 4 " size="3" time="0"/>
  </attr>
  <attr type="GroupAttr" name="point" inheritChildren="false">
    <attr type="FloatAttr" name="P" tupleSize="3">
      <sample value="0.2 0 5 -2.8 0 2.0 0.5 0 1.0 -0.3 0 -1.5 1.8 0
                     4.9 -0.4 0 2.2 2.5 0 1.0 1.6 0 -1.4 3.8 0 4.9
                     1.6 0 2.2 4.5 0 1.0 3.6 0 -1.4"
                     size="36" time="0"/>
    </attr>
  </attr>
</attr>

Type	Attribute	Description
int	geometry.basis	An integer indicating the curve basis. This is defined as follows: 0 - No basis 1 - Bezier 2 - B-Spline 3 - Catmull-Rom 4 - Hermite 5 - Power This follows the BasisType enumeration in the Alembic library.
float	geometry.constantWidth	A float that defines the width of a curve, which is applied uniformly to each control point.
int	geometry.degree	Specifies whether curves are linear (degree = 1) or cubic (degree = 3).
float[]	geometry.knots	Knot vector is a sequence of parameter values. Note When splitting geometry.point.P into multiple curves using knots, the values in numVertices must correspond. For example, given 8 control points in geometry.point.P, degree = 3, and knots = [ 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 ], then numVertices = [ 4 4 ].
int	geometry.vstep	Sets the vertex stride for the curve. This is used by Katana to calculate the expected length of point-scoped arbitrary attribute arrays.
int[]	geometry.numVertices	The number of vertices in each curve. The numVertices list defines the index ranges of the knots used by each curve.
float[3n]	geometry.point.P	List of points. The geometry points are unique floating point positions in object space coordinates (x, y, z). Each point is only stored once but it may be indexed many times by the same knot.
float[3n]	geometry.point.orientation	List of orientations for each control point in the curve, relative to the camera.
float[n]	geometry.point.width	List of widths (diameters) of the curve at each control point. Note If both geometry.constantWidth and geometry.point.width are set, the values in geometry.point.width are used.
float[n]	geometry.arbitrary.width.value	List of widths (diameters) of the curve if the scope is not point or primitive. See Arbitrary Attributes. Note If both geometry.point.width and geometry.arbitrary.width are set, the values in geometry.point.width are used. Note If both geometry.constantWidth and geometry.arbitrary.width are set, the values in geometry.arbitrary.width are used.

locator

Used only in the Viewer; ignored by the renderers.

Type	Attribute	Description
group	geometry.point	See polymesh.
group	geometry.poly	See polymesh.

sphere

Built-in primitive type for a sphere, supported by some renderers.

Type	Attribute	Description
double	geometry.radius	The radius of the sphere.

spheres

A more efficient way of creating a group of spheres in PRMan at once. This is ignored by other renderers.

Type	Attribute	Description
float[3n]	geometry.point.P	List of points that represent the sphere centers.
float[n]	geometry.point.radius	The spheres’ radii.
float	geometry.constantRadius	Can be used instead of geometry.point.radius to specify a single radius for all spheres.