title: Efficiency of perspective projection vs raytracing/ray casting
body: <p>I have a very general question. I wish to determine the boundary points of a number of objects (comprising 30-50 closed polygons (z) each having around 300 points(x,y,z)). I am working with a fixed viewport which is rotated about x,y and z-axes (alpha, beta, gamma) wrt origin of coordinate system for polygons.</p>
  
  <p>As I see it there are two possibilities: perspective projection or raytracing. Perspective projection would seem to requires a large number of matrix operations for each point to determine its position is within or without the viewport.
  Or given the large number of points would I better to raytrace the viewport pixels to object? 
   i.e. determine whether there is an intersection and then whether intersection occurs within or without object(s). 
  In either case I will write this result as 0 (outside) or 1 (inside) to 200x200 an integer matrix representing the viewport</p>
  
  <p>Thank you in anticipation</p>