Computes the winding number of a curve in XY plane around a point.
The winding number indicates how many times a curve “wraps around” a
point. Useful for inside/outside test, the winding number is
approximately one inside of the curve and approximately zero outside.
A point that is half covered by an open
curve will have a winding number approximately equal to 0.5, so
this gives a robust way of defining “inside” as having a winding
number of 0.5 or greater. Reversed curves will have negative
winding numbers inside.
float windingnumber2d(<geometry>geometry, vector origin)
float windingnumber2d(<geometry>geometry, vector origin, float accuracy)
Computes the winding number of the curve ‹geometry› around the point ‹origin›.
float windingnumber2d(<geometry>geometry, string primgroup, vector origin)
float windingnumber2d(<geometry>geometry, string primgroup, vector origin, float accuracy)
Computes the winding number of primitive group ‹primgroup› around the point ‹origin›.
<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.
primgroup
Optionally compute winding number only for a subset of a curve specified by a primitive group.
origin
The position in space to compute winding number.
accuracy
The winding number is computed only approximately. The default value 2.0 is sufficient in most situations, setting ‹accuracy› to 12.0 should yield result accurate up to floating point precision.
Returns
The winding number of a curve at a point in XY plane.
| measure |
|