Abstract: One of the main challenges in real-time rendering is to enable more and more effects that were previously available in offline rendering only. An important effect among these is physically correct reflections of arbitrary objects in curved reflectors like windshields.

In this paper we propose fragment tracing on the GPU as a solution to interactively realizing this effect for large scenes as employed in industrial applications. For each rasterized fragment, a ray is traced through an octree representing the original geometry and surface material. By introducing a GPU implementation of an octree traversal, for the first time hierarchical data structures can efficiently be used on the GPU. As a result, the approach allows both handling of large geometries such as those employed in virtual prototyping and accurate rendering. Several examples show the generality and achievable rendering quality of our method.