Ray Casting

  • Shoot rays through pixels into the world

  • For each object in the display-list compute the intersection of the given ray

  • For each pixel,
    Find closest intersection in scene

  • Evaluate illumination model to color pixel

Compared to Forward Mapping, there are other ways to compute views of scenes defined by geometric primitives. One of the most common is ray-casting.

Ray-casting searches along lines of sight, or rays, to determine the primitive that is visible along it.

Properties of ray-casting:

  • Go through all primitives at each pixel

  • Sample first

  • Analytic processing afterwards

  • Requires a display list

  • Per-pixel evaluation, per-pixel rays (not scan-convert each object)

Usual Graphics Pipeline

 

Ray Casting

E (D | G) L

In a ray-casting renderer the following process takes place.
1. For each "Screen-space" pixel compute the equation of the "Viewing-space" ray.
2. For each object in the display-list compute the intersection of the given ray
3. Find the closest intersection if there is one
4. Illuminate the point of intersection