image formation
DESCRIPTION
Image Formation. (Forward) Ray Tracing. (Backward) Ray Tracing. 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. - PowerPoint PPT PresentationTRANSCRIPT
Raycasting (animated gif)
Image Formation
(Forward) Ray Tracing (Backward) Ray Tracing
Shadow RayWhen 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 RayWhen 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 RayIf 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 TreeThe 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]
Standard MethodRay (O,D)
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Ray vs. Directed Line
CW
CCW
Here, it is looking from the head of ray
Ray-Polygon Intersection with Plucker Coordinates
MMM Ray vs. AABBRepresent 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 ?