Basic Pipeline questions

  1. Why do we need 4x4 matrix for perspective projection ?
  2. Why does a clipping happen in homogenous coordinates and not in NDC (Normalized Device Coordinates) ? What is the algorithm for polygon clipping with homogenous coordinates ?
  3. What does it mean to do a perspective divide ?
  4. During rasterization, for perspective correct interpolation to happen, Is it the inverse of NDC z-coord that gets interpolated or Is it the inverse of the camera space z-coord ? Since rasterization happens after the perspective divide at which point the camera space z-coord is lost.

Sounds a lot like homework questions to me, so don’t expect any answers.

Also, those questions are so generalized, you can look them up in any text-book about computer-graphics. And that’s exactly what you should do.


These are no homework questions. I’m a working profesional trying to learn CG on my own. The questions are designed to know the significance, I don’t see why they are generic. May be you can answer one ? Perhaps you should checkout my previous posts before you conclude I’m a student.

I would appreciate if you could suggest a textbook that has answers to my questions.

3D Math book