title: Reflection off curved surface - HLSL
body: <p>Let's say I have a flat, perfect mirror.  How do I find what it's reflecting?  Easy, move the camera to a position which looks back up at the angle of incidence.</p>
  
  <p>Now what if that flat mirror was curved or spherical?  How would I find the reflection of Object A if Object B was a non-flat, perfect mirror.  </p>
  
  <p>Presumably this would need some kind of ray-tracing (not sure how to do in HLSL ... yet), but I'm guessing this will be a performance killer.  So has anyone done this before and know what to do now? If so, is there an easier way?  How did you do it?</p>
  
  <p>EDIT: This has to work in DX9</p>