Raycasting (animated gif)

Image Formation (Forward) Ray Tracing(Backward) Ray Tracing

Shadow Ray When the ray hits an object, a secondary ray, ("shadow" ray), is shot towards the light sources Determine if that point on the object is in a shadow. If this shadow ray hits another object before it hits a light source, then the first intersection point is in the shadow of the second object. Only apply the ambient term for that light source at the point of intersection

Reflected Ray When a ray hits an object, a reflected ray is generated and tested against all of the objects in the scene. If the reflected ray hits an object then a local illumination model is applied at the point of intersection and the result is carried back to the first intersection point.

Transmitted Ray If the intersected object is transparent, then a transmitted ray is generated and tested against all the objects in the scene. If the transmitted ray hits an object then a local illumination model is applied at the point of intersection and the result is carried back to the first intersection point.

Ray Tree The reflective and/or transmitted rays are continually generated until the ray leaves the scene without hitting any object or a preset recursion level has been reached. This then generates a ray tree. DEMO

Example

Ray Trace vs. Rasterization

AABB tree

How can AABB Tree Help Tracing

Fast Ray-AABB Overlap Tests with Plucker Coordinates Mahovsky and Wyvill [2003]2003

Standard Method Ray (O,D) y=y0 y=y1 Similarly,

0 t 0 t

Ray vs. Directed Line CW CCW Here, it is looking from the head of ray

Ray-Polygon Intersection with Plucker Coordinates

MMM Ray vs. AABB Represent a line this way … is the Plucker coordinate way (MMM: minus,minus,minus) x z

Hw: XXX Ray vs. AABB 想想若是 ray 來自其他方位，該如何測試 ?