invertexgroup

int  invertexgroup(string filename, string groupname, int vertexnum)

int  invertexgroup(int opinput, string groupname, int vertexnum)

<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.

vertexnum

The linear vertex number of the vertex to test.

To convert a primitive number and vertex number within that primitive to a linear vertex number for the vertexnum parameter, use the vertexindex function.

Returns

1 if the group exists and the vertex is in the group, or 0 otherwise.

This can use ad-hoc groups, like 42p0-2. It matches the SOP group naming convention, in particular that an empty string means all vertices.