Object Types

• Polymesh
• Free form surfaces
• Volume
• CSG
• Implicit surfaces

Basic Operations

• Establish priorities among polygons, objects, etc
• Collect overlapping elements and use priorities to resolve visibility

Backface Culling

N = outward normal vector of face

P = a point on face

E = eye vector (from a point on face to eye = E - P)

A face is a front face if:

• In world space: $N\cdot E> 0$ (or the angle between normal end eye is less than 90°)
• In Eye/Camera Space: $N\cdot (-P) > 0$ or $N\cdot P< 0$ (P here is a vector from 0 to P)
• In Projection Space (after prospective division), $N_z < 0$

Algorithm types

• Image Space: operations 1 and 2, both at pixel resolution