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This thesis tests several methods and measures in pathtracing for selecting either the Line Space or the Bounding Volume Hierarchy data structure to make use of the advantages of both. The structures are defined locally around each object and each Line Space shaft contains one candidate ID each. All implementation is done as a C++ and OpenGL framework with compute shaders handling the pathtracing and Line Space generation. The measures include the probability distribution, the effect dependency, as well as a distance threshold and are tested against several different scenes. In most situations, the results show a noticeable increase in performance, partly only with minor visual differences, with the probability measure producing the highest quality images for a given performance. The fundamental problems of the Line Space concering the high memory consumption and a long generation time compared to the BVH still persist, despite the object local structure, a minimal amount of data per shaft and the compute shader implementation.
This thesis presents the use of a local linespace data structure, which is designed and implemented on the basis of an existing GPU-based raytra- cer with a global linespace data structure. For each scene object, an N-tree is generated whose nodes each have a linespace. This saves informations about existing geometry in its shafts. A shaft represents a volume between two faces on the outside of the node. This allows a faster skipping of em- pty spaces during raytracing. Identical objects can access already calcula- ted linespaces, which can reduce the memory requirement by up to 94.13% and the initialization time of the datastructure by up to 97.15%. Due to the local access possibilities dynamic scenes can be visualized. An increase in quality can also be observed.
This thesis presents a novel technique in computer graphics to simulate realtime
global illumination using path tracing. Path tracing is done with compute shaders on the graphics card (GPU) to perform rendering in a highly parallelized manner. To improve the overall performance of tracing rays, the Line Space is used as an acceleration data structure in different variations, resulting in better
empty space skipping. The Line Space saves scene information based on a previous voxelization in direction-dependent shafts and is generated and traversed on the GPU. With this procedure, indirect lighting and soft shadows can be computed in a physically correct way. Furthermore, using the Line Space, path tracing can be performed mostly independent of the complexity of the scene geometry with over 100 frames per second, which is truly real-time and much faster than using a comparable voxel grid. The image quality is not affected negatively by this technique and the shadow quality is in most cases much better compared to shadow-mapping.
This thesis explores different approaches for the acceleration of raytracing calculations on the graphics processing unit (GPU). For that a voxel grid is used and extended by the linespace data structure. The linespace consists of direction based shafts and stores the objects located in those shafts in a candidate list. Different methods for the sorting and traversal of the linespace are presented and evaluated. The shown methods cannot provide a speed up of the frame rate without resulting in a loss of image quality.