GPU-Based Local Tone Mapping in the Context of Virtual Night Driving

Virtual Prototyping of automotive headlights requires a realistic illumination model, capable of rendering scenes of high contrast in fine detail. Due to the high dynamic range nature of headlight beam pattern data, which is projected onto the virtual road, high dynamic range illumination models are required. These are used as the basis for illumination in simulations for automotive headlight Virtual Prototyping. Since high dynamic range illumination models operate on brightness ranges commensurate with the real world, a post-processing operation, known as tone mapping, is required to map each frame into the device-specific range of the display hardware. Algorithms for tone mapping, called tone mapping operators, can be classified as global or local. Global operators are efficient to compute at the expense of scene quality. Local operators preserve scene detail, but, due to their additional computational complexity, are rarely used with interactive applications. Local tone mapping methods produce more usable visualization results for engineering tasks. This paper proposes a local tone mapping method suitable for use with interactive applications. To develop a suitable tone mapping operator, a state of the art local tone mapping method was accelerated using modern, work-efficient GPU algorithms. Optimal performance, both in terms of memory and speed, was achieved by means of General-Purpose GPU programming with CUDA. A prototypic implementation has shown that the method works well with high dynamic range OpenGL applications. In the near future, the tone mapper will be integrated into the virtual night driving simulator at our institute.