Image Formation

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

2. When the ray hits an object, a secondary ray, ("shadow" ray), is shot towards the light sources Shadow Ray 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

3. 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. Reflected Ray

4. 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. Transmitted Ray

5. 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

7. Example

8. Ray Trace vs. Rasterization

9. AABB tree

10. How can AABB Tree Help Tracing

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

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

13. t 0 t 0

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

15. Ray-Polygon Intersection with Plucker Coordinates

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