Ray Tracing - Week 7 Flashcards
What is the definition of a ray?
A line that has an origin point and a direction in 3D space. Represented mathematically as a pair of vectors, one for the origin Ro and one unit vector for the direction Rd
What is the explicit equation of a ray?
An equation for finding a point a given distance from the origin in the direction of the ray.
R(t) = R0 + Rd*t for t >= 0
What effects can classical Whitted raytracing portray?
Reflections, transparency, refraction, shadows, specular highlights (seen in screenshot), depth of field
What concept is used for clicking on an object or shooting a bullet in a straight line?
Raycasting
What was the biggest optimisation Whitted came up with to solve the issues with the basic raytracing concept?
Recognising that not every ray from a light soure hits the camera.
It traces rays from the viewport rather than the light source.
It notes intersections with the light sources as it progresses so you can figure out what happened when you unreverse that process
Describe Whitted raytracing
Fire a ray into the scene from the eye-point through a specific pixel, until it hits something.
Now generate a new type of ray called a shadow feeler ray. Fire one of these in the direction of every light source in the scene. If the ray is not blocked, note this down (we don’t know the full effect of this yet).
Keep going until the ray leaves the scene or runs out of energy or we just decide we have gone far enough down the ray tree and can’t afford to go further.
Repeat this for every other pixel in the viewport
What type of reflection does Classical Whitted not handle? What is the consequences of this?
It ignores the explosion of rays from diffuse reflections instead modelling everything as specular reflectors or as transparent, so everything rendered with this technique looks a bit hard and shiny.
