ATTENTION: This is a web archive! The IMS Group was split up in 2018 and does not exist anymore. Recent work of former members can be found at the VR/AR Group and the Computer Vision Group.

Interactive Media Systems, TU Wien

Fast CPU Ray-Triangle Intersection Method

Thesis by Thomas Alois Pichler

Supervision by Hannes Kaufmann and Peter Kán


Ray tracing is a technique capable of synthesizing highly realistic images. It accurately simulates the physical distribution of light in a scene and can be used for movie production, scientific visualization, in the automotive industry, or by artists or game developers. In this context, rays of light, as well as lines of sight, are represented by "rays" which are traced throughout the scene. Rays interact with objects in the scene (they penetrate them, are reflected, refracted, etc.) and ultimately define the pixel values of the generated image. Thus, one crucial functionality of a ray tracing application is calculating the intersection of rays with scene primitives. One of the most often used primitives is the triangle. It enables relatively simple intersection calculations, and complex objects can be tesselated into triangles. Thus, a ray tracer´s ray-triangle intersection routine is called a considerable number of times per scene. Ray tracing is generally seen as a rather slow method of image generation. Thus, several algorithms for fast ray-triangle intersection have emerged within the last years. In the scope of this thesis, a novel, fast ray-triangle intersection algorithm is implemented into the CPU-based ray tracing framework PBRT. The algorithm features early termination strategies and transforms the ray-plane intersection point into a 2D coordinate system. For this transformation, two different approaches are discussed. Different optimizations are explored to further improve the algorithm´s performance. The algorithm is evaluated against PBRT´s default algorithm and against another state-of-the-art ray-triangle intersection algorithm in terms of efficiency. Realistic scenes with different ray-triangle hit-rates and different scene complexity are used for the tests. The results show that the new algorithm outperforms the default algorithm for every scene.


T. Pichler: "Fast CPU Ray-Triangle Intersection Method"; Supervisor: H. Kaufmann, P. Kán; Institute of Visual Computing and Human-Centered Technology, 2018; final examination: 10-01-2018.


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