G5: Ray Tracing Flashcards
What is ray tracing?
One of the 2 families of rendering algorithms
What is the key idea behind ray tracing?
Reverse light path direction
What does ray casting involve?
“Shoot” ray through each pixel
List the steps in the ray casting algorithm.
- Loop over pixel sample points p on the 2d image plane
- For each of these points, construct ray from camera origin through p
- Check each object o in the scene for intersections
- Compute distance from ray origin to surface of object if intersected
- Store distance in min_t if less than current min_t
- Use spatial acceleration structures to speed up object checks
What is the parametric equation for a ray?
r(t) = o + td
What does ‘d’ represent in the ray equation?
Direction vector towards the point p
What types of intersection tests are used in ray intersection?
- Ray-triangle
- Ray-box
- Ray-sphere
What is the implicit equation for a sphere?
All pts x where f(x) = 0
How do you find the intersection of a ray with a sphere?
Replace x with r and solve for t
What is the example function for a unit sphere?
f(x) = |x|² - 1
What is the relationship between ray casting and ray tracing?
Ray tracing involves recursive ray casting
What is meant by direct illumination in ray tracing?
Single bounce
Define global illumination in the context of ray tracing.
Multiple bounces for more realistic lighting
What are the computational challenges of ray tracing?
Exponential computations with respect to number of intersections/bounces
What is a key advantage of ray tracing?
Elegantly simple but expensive, captures complex lighting and shading
What is rasterization?
Loop over triangles first
List the advantages of rasterization.
- Never have to store entire scene
- Supports unbounded size scenes
What does ray tracing require in terms of scene storage?
Must store entire scene
What is a natural order for rendering transparent surfaces in ray tracing?
Process surfaces in the order they are encountered along the ray: front-to-back or back-to-front
True or False: Ray tracing is the algorithm of choice for visual effects in movies.
True
