Abstract—The recent emergence of programmable GPUs on mobile devices means that mobile ray tracing at interactive rates is imminent. Previous work has focused mainly on speeding up real-time ray tracing. However, on a mobile device, the most constraining resource is frequently its available battery energy. In addition to maintaining reasonable frame rates and image quality, ray tracing on mobile devices must also be energy efficient. We present results of a comprehensive measurement study that investigates the energy efficiency of mobile ray tracing. We compared the energy efficiency of uniform grid, k-d tree, and bounding-volume hierarchy (BVH) acceleration structures on scenes ranging in size from 1lk to 990k triangles when rendered on both the CPU and GPU. Our results show that from an energy perspective, several scene characteristics such as the number and distribution of triangles, mobile display size, and the rendering processor (CPU vs. GPU) can affect which acceleration structure is most energy efficient. With the exception of the SAH k-d tree, the build energy of all acceleration structures was much smaller than the rendering energy, making the SAH k-d tree a bad choice energy wise for highly dynamic scenes. For small screen sizes (e.g., cell phone resolutions), rendering on the CPU using a naïve k-d tree uses less energy than any other processor-acceleration structure combination. On the GPU, the BVH is the most energyefficient acceleration structure for larger screen sizes (e.g., PDA and laptop resolutions), regardless of model size
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