Ray tracing

Question 1

What is the main difference between rasterization and ray tracing?

Answer 1

• Rasterization: processes each object, then each pixel it covers
• Ray tracing: processes each pixel, then checks all objects in that direction

Question 2

How does rasterization handle visibility?

Answer 2

It uses a depth buffer to keep the closest fragment for each pixel

Question 3

How does ray tracing handle visibility?

Answer 3

It casts a ray per pixel and keeps the closest object hit by that ray

Question 4

How do lighting and shadows differ in rasterization and ray tracing?

Answer 4

• Rasterization: estimates lighting using formulas; shadows need hacks (like shadow maps)
• Ray tracing: simulates lighting with real ray bounces and handles shadows naturally

Question 5

What is a key similarity between ray tracing and ray marching?

Answer 5

Both start by casting a ray from each pixel into the scene

Question 6

What is the main difference in how rays are processed between ray tracing and ray marching?

Answer 6

• Ray marching: takes many small steps using distances from SDFs
• Ray tracing: directly checks for ray-object intersections and can bounce rays recursively

Question 7

What kind of scene definition does ray marching use?

Answer 7

A Signed Distance Field: a function that returns the shortest distance from a point to the nearest surface.

Question 8

What kind of scene definition does ray tracing use?

Answer 8

An intersection function: returns the closest surface hit along a ray direction.

Question 9

What is a BVH?

Answer 9

A Bounding Volume HierArchy is a tree of bounding boxes around groups of objects, used to speed up intersection tests.

Question 10

Why is a BVH useful for ray tracing?

Answer 10

It avoids testing the ray against every single object, reducing computations.

Question 11

How is a BVH constructed?

Answer 11

• Objects are wrapped in bounding boxes
• These are grouped recursively into parent nodes
• Each parent node contains the bounds of all its children

Question 12

How is a BVH used during ray tracing?

Answer 12

• Rays are tested against the BVH root
• if a node is hit, its children are tested
• The process repeats until leaf nodes (actual geometry) are reached

Question 13

What are the main benefits of ray tracing?

Answer 13

• Better reflections (can show things off-screen)
• Better shadows (soft, transparent, no resolution limits)
• Better transparency and refraction (no need for sorting)

Question 14

What are the limitations of ray tracing?

Answer 14

• Must test collisions with all (or many) objects
• Complexity grows fast with recursive rays
• Needs many rays for good quality -> leads to noise and high performance cost