Want to find an attribute on a specific polygon? Want to stick an object to another piece of geometry? XYZdist and PrimUV are the solutions.
XYZdist returns the distance between an "origin" (often v@P, "the current geometry") and a "specified geometry".
It also returns what prim number is closest to each point, and where on that prim that point lands (the parametric uv).
written out in plain language, the xyzdist function reads like this:
find the closest distance between point "origin" and the current geometry. Also, tell me what prim each point belongs to and where on that prim.
xyzdist("specified geometry via input", "origin, often v@P", prim, uv)
PrimUV reads an interpolated parametric UV attribute from a specific primitive.
It requires a prim, and a parametric uv coordinate on that prim to lookup the attribute.
That's why XYZdist and PrimUV are used together - XYZdist supplies PrimUV the prim number and uv coordinate for it to look up an attribute.
See the attached HIP file for more examples.