Interactive deformation and visualization of large volume datasets

This paper presents an integrated approach for interactive direct volume deformation and simultaneous visualization. The fundamental requirement is that interactive performance without pre-processing must be achieved for large volume data, where at any time up to one million elements participate in a deformation that is applied interactively by picking and dragging in the 3D view. Current physically-based approaches are still one or two orders of magnitude away from this goal. In contrast, our approach extends the non-physical ChainMail algorithm and combines it with on-the-fly resampling and GPU ray-casting. Special transfer functions assign material properties depending on volume density. The affected subvolume is deformed and resampled onto a rectilinear grid on the CPU, and updates the volume on the GPU where it is rendered using ray-casting. While the deformation is already being displayed, its quality is simultaneously refined via an iterative relaxation procedure executed in a parallel thread.