Ray tracing using accelerated shadow testing schemes

Abstract

The main objective of this dissertation work is to develop two new data structures for storing three-dimensional objects that accelerate the shadow testing and the secondary ray tracing during ray tracing. One is called a shadow pyramid in which all the candidate objects possibly blocking the path from the relevant light source to any point on the primitive object are registered. Shadow testing of the intersection point then performed only against the objects registered in the shadow pyramid. Two hybrid shadow testing schemes based on the conditional switching between the conventional cell traversal scheme and the shadow pyramid scheme are proposed. The other is called a reflection(refraction) frustum in which three-dimensional objects are enrolled at the first impingement of the primary ray onto each polygon when they are potentially intersected with the first reflection(refraction) ray. Only those objects registered in the corresponding frustum are checked for intersection with the secondary rays emanating from the same polygon. To reduce the number of ray-object intersection calculations, we exploits some kinds of coherences such as special treatment of the object, intersected at the previous pixel, usage of the sorted list of the registered objects, and discard of some registered objects no longer be intersected with the succeeding rays. Due to the fast access of the candidate objects for intersection and reduced number of intersection calculations, the total ray tracing time of the proposed scheme is more than two times faster than that of the conventional cell traversal scheme based on the uniform subdivision for the experimental scenes used in this thesis. Soft shadows are generated by extending the shadow pyramid to the shadow hull which enable us to handle linear and area light sources. To get the further realistic output image, color texturing and antialiasing techniques are also implemented.