Background. Real-time shadows in 3D applications have for decades been implemented with a solution called Shadow Mapping or some variant of it. This is a solution that is easy to implement and has good computational performance, nevertheless it does suffer from some problems and limitations. But there are newer alternatives and one of them is based on a technique called Voxel Cone-Tracing. This can be combined with a technique called Cascading to create Cascaded Voxel Cone-Tracing Shadows (CVCTS). Objectives. To measure the computational performance of CVCTS to get better insight into it and provide data and findings to help developers make an informed decision if this technique is worth exploring. And to identify where the performance problems with the solution lies. Methods. A simple implementation of CVCTS was implemented in OpenGL aimed at simulating a solution that could be used for outdoor scenes in 3D applications. It had several different parameters that could be changed. Then computational performance measurements were made with these different parameters set at different settings. Results. The data was collected and analyzed before drawing conclusions. The results showed several parts of the implementation that could potentially be very slow and why this was the case. Conclusions. The slowest parts of the CVCTS implementation was the Voxelization and Cone-Tracing steps. It might be possible to use the CVCTS solution in the thesis in for example a game if the settings are not too high but that is a stretch. Little time could be spent during the thesis to optimize the solution and thus it’s possible that its performance could be increased.

This thesis explores Voxel Cone Tracing as a possible Global Illumination solutionon mobile devices.The rapid increase of performance on low-power graphics processors hasmade a big impact. More advanced computer graphics algorithms are now possi-ble on a new range of devices. One category of such algorithms is Global Illumi-nation, which calculates realistic lighting in rendered scenes. The combinationof advanced graphics and portability is of special interest to implement in newtechnologies like Virtual Reality.The result of this thesis shows that while possible to implement a state of theart Global Illumination algorithm, the performance of mobile Graphics Process-ing Units is still not enough to make it usable in real-time.

Voxel cone tracing (VCT) is a rendering method designed to approximate global illumination in a fast and efficient way. Global illumination means to render not only the direct lighting of a scene but also light from indirect sources, simulating how light in the real-world tend to bounce around and illuminate even the areas that are occluded from a direct light source. Rendering accurate global illumination in real-time has for a long time been a challenge in the field of computer graphics. This effect is most accurately simulated through expensive algorithms such as path tracing, where individual rays of light are traced from the pixels of a camera as they bounce around the scene and sample the environment. More efficient methods tend to rely on static image-based approaches, where global illumination is pre-rendered and baked into textures. VCT presents itself as a middle ground of the two, trading some of the accuracy for improved performance and the ability to work in a fully dynamic environment where objects and light sources may be moved around. VCT computes global illumination by volumetrically sampling a lower resolution voxel-based representation of the rendered scene by tracing cones.   The aim of this thesis is to further investigate the performance and image quality of VCT through an implementation and evaluation method. A VCT algorithm has been implemented that is capable of real-time global illumination in a dynamic setting, utilizing physically based rendering for improved image quality and a sparse 3D texture for efficient voxel storage. Performance was then measured in terms of rendering speed and memory usage. Image quality was evaluated through comparison with accurate path traced reference images. The results show that VCT is a promising rendering method for achieving a real-time approximation of global illumination, but that it also suffers from some issues regarding the image quality.

This thesis deals with the global illumination in the scene by using Voxel Cone Tracing method. It is based on the voxelization of a triangle mesh scene. The voxels can be stored to a full regular 3D grid (texture) or to the hierarchic Sparse Voxel Octree for saving of the memory space. This voxel representation is further used for computations of the global indirect illumination in real time within normal triangle mesh scenes for more realistic final image. Values from the voxels are obtained by tracing cones from the pixels which we want to get illumination for.

This thesis that implemented Monte Carlo path tracing and voxel cone tracing for global illumination on GPU compared the performance and visual result. The Monte Carlo path tracing algorithm is implemented in CUDA to do parallel computing on GPU and accelerate the computing speed. The voxel cone tracing, a global illumination algorithm for real-time computing, runs on OpenGL through the GPU graphics pipeline. The results show that the Monte Carlo Path Tracing on CPU single core takes over 10 hours, around 4 hours with 4 cores, on GPU it takes around 48 minutes, while the voxel cone tracing on the same GPU takes 2 ms. The quality of the image generated by the Monte Carlo path tracing contains much more transparent, reflection, and shadow details than that using the voxel cone tracing algorithm. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>