Multiresolution ViewDependent Splat Based Volume Rendering of Large

Multiresolution View-Dependent Splat Based Volume Rendering of Large Irregular Data Jeremy Meredith, Lawrence Livermore National Laboratory Kwan-Liu Ma, University of California, Davis University of Illinois at Chicago

Multi-res View-Dependent Splatting • Highlights: – Visualize very large irregular data interactively • Pro: – Multi-res: hierarchical oct-tree – View-dependent – Splatting • Con: – Oct-tree add much overhead to store volume data University of Illinois at Chicago

Multi-resolution • Hierarchical oct-tree University of Illinois at Chicago

Splatting • Integral of emitted light at each point on image plane University of Illinois at Chicago

Splatting • Low-Albedo Optical Model – The amount of emitted light received at location x at the image plane – Use Taylor approximation • Here, If If(x) is the amount of light at location x in the frame buffer, and αnew(x), Inew(x) are the new incoming opacities and light intensities, respectively – Open. GL blending function • gl. Blend. Func(GL SRC ALPHA, GL ONE MINUS SRC ALPHA) University of Illinois at Chicago

EVL Internal Volume Visualization Workshop Charles Zhang EVL, UIC University of Illinois at Chicago

Our Goals • Very large data – Difficulties: WAN, beyond local RAM, interactivity – Is multi-res necessary? • Pro: fast access, exploration convenient, scalability, pre-fetch compatible • Con: a pre-processing must • Which mutli-res: wavelet? – Is view-dependence necessary? • Pro: no redundant data fetch, easy pre-fetching, good for stereodisplay(? ) • Con: overhead? • Parallel Volume Rendering – Image-ordering or object ordering? • IO: accurate • OO: fast, suitable for view-dependence – Sort-first or sort-last • Sort-first uses less bandwidth University of Illinois at Chicago

Our Goals (cont’d) • Interactivity – Fast overview? • Multi-res, view-dependent? – Fast view point change? • Tolerance is high when view moving fast. • Distributed / Parallel Computing – Distributed data on WAN? • Is the data scalable, what’s the limit for our viz tools – Load-balancing on rendering cluster – Multi-tile display • The display is scalable? University of Illinois at Chicago