Simultaneous GPU-Assisted Raycasting of Unstructured Point Sets and Volumetric Grid Data

In the recent years the advent of powerful graphics hardware with programmable pixel shaders enabled interactive raycasting implementations on low-cost commodity desktop computers. Unlike slice-based volume rendering approaches GPU-assisted raycasting does not suffer from rendering artifacts caused by varying sample distances along different ray-directions or limited frame-buffer precision. It further supports direct implementations of many sophisticated acceleration techniques and lighting models. In this paper we present a GPU-assisted raycasting approach for data that consists of volumetric fields defined on computational grids as well as unstructured point sets. We avoid resampling the point data onto proxy grids by directly encoding the point data in a GPU-octree data structure. This allows to efficiently access the (semitransparent) point data during ray traversal and correctly blend it with the grid data, yielding interactive, highquality rendering results. We discuss approaches to accelerate the rendering performance for larger point sets and give real world application examples to demonstrate the usefulness of our approach.