Fig 9. Neurosurgical application of the orientation-dependent transparency rendering method.

The left column shows a high resolution T1-weighted image for anatomical reference. The middle column shows conventional streamline rendering, where the tumor (gray) is largely covered by the massive amount of streamlines. The right column shows that orientation-dependent transparency rendering (α _decreasing with c = 4) allows for in-depth visualization of a tumor mass by rendering streamlines that are running towards the viewing axis transparent. Fig (a), (b) and (c) show superior, anterior, and lateral views, respectively. In (d), the tumor volume is used as an ROI for the selection of relevant streamlines. By fixing the opacity axis along the antero-posterior direction (α _increasing with c = 4), one can render Cg streamlines opaque, showing that they penetrate the tumor area.