Filename In Prim_attribute + Other Attribute Questions.

[emcjagger]

Hi folks,

I'm trying to get an attribute (P) from primitives using UV coordinates in VEX code, much as one would with the primuv() expression. The prim_attribute function seems like it should fit the bill. The help shows usage like this:

int prim_attribute(string filename; vector &adata; string att; int pn; float u; float v)

I assumed that the "filename" could be a houdini operator. I tried directing it to the appropriate sop, but it only sort of sometimes worked for a smattering of the points, and always returned 0. Am I missing something?

A related general question about attributes: is it generally quicker to add attrs in your own custom vex op, than in an AttribCreate sop? My tests so far seem to suggest so. I already have a way of doing the above using primuv() and a Point sop, but I figured it would be faster in a vex sop, especially since I'm setting P so I currently have to call primuv() 3 times (xyz).

Finally, is there a way to get attrs mapped to variables (eg. myAttr -> MYATTR) when they're added in a vex op, the way they are with AttribCreate sops? And is there a way to get custom vex ops to recognize attribute variables in parameters the way other ops do ($PT, $TX, etc.)?

Many thanks!

Jeremy.

Edited February 7, 2007 by emcjagger