1. Rendering method:
Rasterization: object -> pixel, fast, cannot handle global illumination
Ray Tracing: Pixels -> Objects, Slow
二、Whitted-Style Ray Tracing：
1) The light starts from the eyes to find the intersection point with the object:
Compute the intersection of a ray with a face (implicit, triangle), whichever is closest
Use AABB (axis-aligned collision box) to reduce the amount of calculation, how to judge the intersection of light and box (as 3 sets of alignment planes):
Space division (KD-Tree), object division (BVH, more extensive)
3. The Rendering Equation rendering equation:
Light intensity = self-illumination intensity + light intensity received by other objects
Solving the integral method: Monte Carlo integral, select the light according to a certain distribution probability, and finally calculate the average
4. Path tracing: reduce the amount of calculation
Only one ray is taken during Monte Carlo integral sampling, and multiple rays are traced from the same pixel to take the average to reduce noise.
Recursive Stopping Condition: Russian Roulette
Reduce invalid sampling of rays (rays into the air): Sampling with the distribution probability of the solid angle of the object
