Implicit Adaptive Volume Ray-Casting

In this work we present an acceleration technique for direct volume rendering, that is based on a preprocessing step. This transforms the original uniform grid into an adaptively reduced tetrahedral grid. The basic idea is to exploit the inherent adaptivity information of the reduced grid for the ray integration with importance sampling. An integration step is always performed from cell face to cell face. This way every cell along the ray is sampled and the integration step size correlates with the tetrahedra volume. In contrast to standard integration techniques no extrapolation or higher order integration for error estimation and step size control is necessary. This guarantees extra acceleration and avoids the problem of missing details if the step size becomes too large. Experiments are made to show the quality of the images obtained and the speed up in contrast to standard volume ray-casting techniques. keywords: adaptivity, irregular grids, volume ray-casting