CellProjection of Convex Polyhedra Stefan Roettger Thomas Ertl

2 Introduction • Unstructured volume rendering • Cell-projection = PT algorithm of Shirley and

Emissive Optical Model • Use emissive optical model (Max ‘ 95) • Does not

Projection of Convex Polyhedra • The graphics hardware can take over the projection of

5 PCP Algorithm • 1 st pass – enable A writing and front face

6 Performance • Emissive model: 212, 000 hex/s on NVIDIA Ge. Force 3 (Guthe

7 Example Images Bluntfin 8 fps Campfire 50 fps Neghip 22 fps Cell-Projection of

8 Ground Fog • Triangulated terrain • Place prism on every base triangle •

9 Emission vs. MIP 25 fps Cell-Projection of Convex Polyhedra Stefan Roettger, University of

10 Fin Thanks for your attention! Cell-Projection of Convex Polyhedra Stefan Roettger, University of

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Cell-Projection of Convex Polyhedra Stefan Roettger Thomas Ertl University of Erlangen

2 Introduction • Unstructured volume rendering • Cell-projection = PT algorithm of Shirley and Tuchman (’ 90) • Main bottlenecks: sorting and tetrahedral decomposition (Wittenbrink ‘ 99) • Current performance 600, 000 tet/s (Guthe ‘ 02) • Above 1, 000 tet/s performance is completely memory bandwidth limited Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo

Emissive Optical Model • Use emissive optical model (Max ‘ 95) • Does not require sorting • Ray integral = length of ray segment times average emission (assuming linear interpolation) Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo 3

Projection of Convex Polyhedra • The graphics hardware can take over the projection of arbitrary convex polyhedra • Based on bounded layered fog (Mech JGT ‘ 01) Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo 4

5 PCP Algorithm • 1 st pass – enable A writing and front face culling – draw primitive with alpha=(d-min d)/ d • 2 nd pass – enable subtractive blending and back face culling – draw primitive again • 3 rd pass – disable A writing and culling – enable additive blending with alpha multiplied – draw primitive with rgb=emission/2 Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo

6 Performance • Emissive model: 212, 000 hex/s on NVIDIA Ge. Force 3 (Guthe ‘ 02: 120, 000 hex/s) • For maximum intensity projection one only needs to render each face once • Performance is about 600, 000 hex/s • Performance drop is mainly due to additional passes Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo

7 Example Images Bluntfin 8 fps Campfire 50 fps Neghip 22 fps Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo

8 Ground Fog • Triangulated terrain • Place prism on every base triangle • Assume constant emission in each prism Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo

9 Emission vs. MIP 25 fps Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen 50 fps Volume Graphics ‘ 03 Tokyo

10 Fin Thanks for your attention! Cell-Projection of Convex Polyhedra Stefan Roettger, University of Erlangen Volume Graphics ‘ 03 Tokyo