Context. The rendering techniques in games have the goal of shading the scene with as high of a quality as possible while being as efficient as possible. With more advanced tools being developed such as a compute shader. It has allowed for more efficient speed up of the shading process. One rendering technique that makes use of this, is Forward plus rendering. Forward plus rendering make use of a compute shader to perform a culling pass of all the lights. However, not all computers can make use of compute shaders. Objectives. The aims of this thesis are to investigate the performance of using the CPU to perform the light culling required by the Forward plus rendering technique, comparing it to the performance of a GPU implementation. With that, the aim is also to explore if the CPU can be an alternative solution for the light culling by the Forward plus rendering technique. Methods. The standard Forward plus is implemented using a compute shader. After which Forward plus is then implemented using CPU multithreaded to perform the light culling. Both versions of Forward plus are evaluated by sampling the frames per second during the tests with specific properties. Results. The results show that there is a difference in performance between the CPU and GPU implementation of Forward plus. This difference is fairly significant as with 256 lights rendered the GPU implementation has 126% more frames per second over the CPU implementation of Forward plus. However, the results show that the performance of the CPU implementation of Forward plus is viable. As the performance stays above 30 frames per second with less than 2048 lights in the scene. The performance also outperforms the performance of basic Forward rendering. Conclusions. The conclusion of this thesis shows that multi-threaded CPU can be used for culling lights for Forward plus rendering. It is also a viable chose over basic Forward rendering. With 64 lights the CPU implementation performs with 133% more frames per second over the basic Forward rendering.

Background. In this experiment forward, deferred and tile-based forward rendering techniques are implemented to research about the light-rendering performance of these rendering techniques. Nowadays most games and programs contains a graphical content and this graphical content is done by using different kind of rendering operations. These rendering operations is being developed and optimized by graphic programmers in order to show better performance. Forward rendering is the standard technique that pushes the geometry data through the whole rendering pipeline to build up the final image. Deferred rendering on the other hand is divided into two passes where the first pass rasterizes the geometry data into g-buffers and the second pass, also called lighting pass, uses the data from g-buffers and rasterizes the lightsources to build up the final image. Next rendering technique is tile-based forward rendering, is also divided into two passes. The first pass creates a frustum grid and performs light culling. The second pass rasterizes all the geometry data to the screen as the standard forward rendering technique. Objectives. The objective is to implement three rendering techniques in order to find the optimal technique for light-rendering in different environments. When the implementation process is done, analyze the result from tests to answer the research questions and come to a conclusion. Methods. The problem was answered by using method "Implementation and Experimentation". A render engine with three different rendering techniques was implemented using C++ and OpenGL API. The tests were implemented in the render engine and the duration of each test was five minutes. The data from the tests was used to create diagrams for result evaluation. Results. The results showed that standard forward rendering was stronger than tile based forward rendering and deferred rendering with few lights in the scene.When the light amount became large deferred rendering showed the best light performance results. Tile-based forward rendering wasn’t that strong as expected and the reason can possibly be the implementation method, since different culling procedures were performed on the CPU-side. During the tests of tile-based forward rendering there were 4 tiles used in the frustum grid since this amount showed highest performance compared to other tile-configurations. Conclusions. After all this research a conclusion was formed as following, in environments with limited amount of lightsources the optimal rendering technique was the standard forward rendering. In environments with large amount of lightsources deferred rendering should be used. If tile-based forward rendering is used, then it should be used with 4 tiles in the frustum grid. The hypothesis of this study wasn’t fully confirmed since only the suggestion with limited amount of lights were confirmed, the other parts were disproven. The tile-based forward rendering wasn’t strong enough and the reason for this is possibly that the implementation was on the CPU-side.