Render particle system as different geometry

Hi - I’m trying to drive some geometry manipulations from a texture. I’ve got a GLSL mat taking in a texture and a bunch of points, set up like a normal GPU particle system. In the end though, I’d like to render the system as boxes instead of particle points. Is there a way to do this? Is there a way to output or overwrite attributes on the points so that I can get the manipulation information?

Thanks,
B