This is something I should have figured out by now, but...

I've imported an animated Poser figure into Vue and applied a single material to all its parts collectively. When I render the animation, the Poser figure works exactly as it should, but the material I applied doesn't "stay put." For example, there's a rust spot on the knee in the first frame, but as the knee moves, the rust spot doesn't stay at the knee but instead moves around on the leg.

How do I apply the material in such a way that the rust spot stays on the knee no matter where the knee goes?

Thanks!