float vertexcurveparam(<geometry>geometry, int linearindex)
<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.
linearindex
The linear index of a vertex
Returns
The parametric coordinate along the perimeter of the primitive. The primitive is assumed to be a polygon. This is in unit space (See primuv for a distription of parameter spaces).
For open polygons (polygon curves in other words), the returned value can
be used directly with primuv. It is in the range of [0,1].
For closed polygons the value is in the range of [0, (numvtx-1)/numvtx], so
there’s no vertex with value 1. The value cannot be used directly with
primuv, but may be useful wherever you need a normalized value around
the perimeter of a polygon.
Examples ¶
This is roughly equivalent to the following code:
int closed = primintrinsic(0, "closed", @primnum); float u = float(vertexprimindex(opname, @vtxnum)) / (closed ? @numvtx : @numvtx-1);
Look up a ramp using the current point’s location on the curve:
// Find the curve parameter of the current vertex and use it // to look up a ramp parameter. // Note that @vtxnum also works when iterating over points. float u = vertexcurveparam(0, @vtxnum); // convert to unitlen space, to correct for points unevenly distributed along // the curve u = primuvconvert(0, u, @primnum, PRIMUV_UNIT_TO_UNITLEN); @width = chramp("width", u);
Look up an attribute on another curve, at the equivalent location. This corrects for unevenly distributed points on either curve.
// Note that @vtxnum also works when iterating over points. float u = vertexcurveparam(0, @vtxnum); // convert to unit length space, to correct for points unevenly distributed // along the curve u = primuvconvert(0, u, @primnum, PRIMUV_UNIT_TO_UNITLEN); // convert back to unit space on another curve. We're using the equivalent // curve in the second input. int otherinput = 1; int otherprim = @primnum; u = primuvconvert(otherinput, u, otherprim, PRIMUV_UNITLEN_TO_UNIT); // look up the value using the correct u coordinate. @P = primuv(otherinput, "P", otherprim, u);
| See also | |
| prim |
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| vertex |
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