From Scene to Image
Connecting the previous calculations produces an image. Knowing which stage changes each value helps locate the cause of a rendering problem.
Object coordinates → world placement → camera coordinates
→ projection and clipping → screen samples
→ visibility, material, and lighting → pixel colors
Implementations may combine or reorder some operations. This diagram distinguishes their purposes.
Another route to a color
Rasterization finds which samples a triangle covers. Ray tracing asks what a camera ray intersects. At an intersection, it evaluates material and light and may send further rays for reflection or refraction.
Global illumination includes light transferred through multiple surface interactions. Tracing one ray does not automatically solve it. Traditional radiosity focuses primarily on energy exchange among diffuse surfaces. Choose a method according to the surfaces and effects being modeled.
Images for two eyes
Stereo images can be rendered from two slightly separated cameras and shown to the corresponding eyes. Differences between the views provide depth cues. Shifting a single image sideways as a whole does not correctly reproduce relationships at all depths.
Final exercise
A camera at the origin looks along +z. Project a triangle with vertices (-1,-1,2), (0,1,2), and (1,-1,2), using focal distance 1. Its unit normal and light direction are both (0,0,-1).
- What are the projected coordinates?
- What is the simple Lambert diffuse factor?
- What appears if a nearer opaque surface covers the same screen location?
Show explanation
The coordinates are (-0.5,-0.5), (0,0.5), and (0.5,-0.5), dividing by depth 2. The normal-light dot product is 1, so the diffuse factor is 1. A nearer opaque surface that passes the depth test is visible instead. Position, brightness, and visibility are separate calculations.