@InProceedings{roettger-volvis02,
  author = {S. Roettger and Th. Ertl},
  title  = {{A Two-Step Approach for Interactive Pre-Integrated Volume Rendering of Unstructured Grids}},
  year   = {2002},
  pages  = { },
  booktitle = {{Proc. IEEE VolVis '02}}
}