primduv

vector  primduv(<geometry>geometry, int prim_number, vector2 uv, int du, int dv)

<geometry>

When running in the context of a node (such as a wrangle SOP), this argument can be an integer representing the input number (starting at 0) to read the geometry from.

Alternatively, the argument can be a string specifying a geometry file (for example, a .bgeo) to read from. When running inside Houdini, this can be an op:/path/to/sop reference.

prim_number

The number of the primitive on which to measure the derivative.

uv

The parametric coordinates on the primitive at which to measure the derivative.

du, dv

Represent the derivative order to query.

On a curve, the curve direction is given by du==1 and the curvature is given by du==2.

dv is used for parametric surfaces.