The viewing Frustum

• glOrtho produces a rectangular view volume
  • Items are clipped against this volume
  • And a parallel projection is performed to create a 2D image.
  • Essentially lines are projected parallel to the z axis
  • Look at the output of projection.C
• glFrustum(left, right, bottom, top, near, far)
  • Defines a frustum
  • 
  • Shapes are distorted, but the way we would like them to be.