Comparing GPU-based multi-volume ray casting techniques

The most essential technique to visualize 3D scalar data is direct volume rendering. For many applications it is necessary that two or more 3D data are visualized simultaneously. We present an overview of data intermixing techniques for visualization with the direct volume rendering technique ray casting. The techniques are Classification Level Intermixing, Accumulation Level Intermixing and Image Level Intermixing. The algorithms are implemented on the Graphics Processing Unit (GPU) in order to be able to interact with the visualization in real-time. We use the new CUDA technology from Nvidia for that. We compare performance by measuring frames per seconds (FPS) and analyzing image quality with criteria contrast and depth effect. Depth effect is determined by a small user study. In most cases Accumulation Level Intermixing is the best choice.