Hardware-Accelerated Ray Tracing of Implicit Surfaces : A study of real-time editing and rendering of implicit surfaces

Abstract: Background. Rasterization of triangle geometry has been the dominating rendering technique in the real-time rendering industry for many years. However, triangles are not always easy to work with for content creators. With the introduction of hardware-accelerated ray tracing, rasterization-based lighting techniques have been steadily replaced by ray tracing techniques. This shift may signify the opportunity of exploring other, more easily manipulated, geometry-type alternatives compared to triangle geometry. One such geometry type is implicit surfaces. Objectives. This thesis investigates the rendering speed, editing speed, and image quality of different implicit surface rendering techniques using a state-of-the-art, hardware-accelerated, path tracing implementation. Furthermore, it investigates how implicit surfaces may be edited in real time and how editing affects rendering. Methods. A baseline direct sphere tracing algorithm is implemented to render implicit surfaces. Additionally, dense and narrow band discretization algorithms that sphere trace a discretization of the implicit surface are implemented. For each technique, two variations that provide potential benefits in rendering speed are also tested. Additionally, a real-time implicit surface editor that can utilize all the mentioned rendering techniques is created. Rendering speed, editing speed, and image quality metrics are captured for all techniques using different scenes created with the editor and an existing hardware-accelerated path tracing solution. Image quality differences are measured using mean squared error and the image difference evaluator FLIP. Results. Direct sphere tracing achieves the best image quality results but has the slowest rendering speed. Dense discretization achieves the best rendering speed in most tests and achieves better image quality results compared to narrow band discretization. Narrow band discretization achieves significantly better editing speed than both direct sphere tracing and dense discretization. All variations of each algorithm achieve better or equal rendering and editing speed compared to their standard implementation. All algorithms achieve real-time rendering and editing performance. However, only discretized methods display real-time rendering performance for all scenes, and only narrow band discretization displays real-time editing performance for a larger number of primitives. Conclusions. Implicit surfaces can be rendered and edited in real time while using a state-of-the-art, hardware-accelerated, path tracing algorithm. Direct sphere tracing degrades in performance when the implicit surface has an increased number of primitives, whereas discretization techniques perform independently of this. Furthermore, narrow band discretization is fast enough so that editing can be performed in real time even for implicit surfaces with a large number of primitives, which is not the case for direct sphere tracing or dense discretization.