Visualization of Industrial Structures with Implicit GPU Primitives Rodrigo de Toledo Bruno Levy

Plan Motivation Previous work Our contributions –New GPU primitives –Implicit information on GPU –Study-cases Results Conclusions

Motivation Problem statement: Interactive visualization of massive models is very difficult –Too much primitives (triangles) Proposition: Whenever it is possible, use implicit GPU primitives rather than triangles –Example: power plant 13 M triangles 200K implicit primitives + 1M triangles (2x speed-up + quality) Reverse engineering

Previous Work (1/3) Extended GPU primitives: –2004, “Extending the graphic pipeline with new GPU-accelerated primitives” –Quadrics:

GPU primitives Ray cast Z-buffer update Freely combined with triangle meshes Advantages: –Quality Computations by pixel Silhouette, phong etc… –Speed Very simple fragment shaders LOD behavior –Memory Represented by few parameters

Previous Work (2/3) ISVC 2007, “Iterative Methods for Visualization of Implicit Surfaces on GPU” –Cubics and Quartics –TORUS

Multiple Tori GPU primitives are faster tori –Newton at 50 fps –the others < 1fps GeForce 7900

Previous Work (3/3) TMCE 2008, “Reverse Engineering for Industrial- Environment CAD Models” –Industrial environments are mainly composed by tubular structures (90%) –Topological approach QuadricsTorus

Our contributions New GPU primitives –Billboard cylinder –Truncated cone –Torus slice Implicit information encoded on GPU memory –Floating-point texture Two study-cases –Power-plant –Oil platform

Cylinders Billboard –only 4 vertices –tight projection enclosing the cylinder perspectiveorthographic gl_RECT(-1,-1,1,1); or gl_RECT(-u,-v,u,v);

View-dependent coordinate system Computing perspective Cylinders

Including caps on cylinders in perspective Cylinders

Truncated and complete cones Cones

Torus slices Adaptive polyhedra Up to 180º Very useful for CAD

Grouping primitive parameters Floating-point texture (each texel 4 scalars) Read by vertices Double speed Our biggest example only uses 10MB (340k primitives)

Study cases Power plant 13M triangles Oil platform 27M triangles

Reverse Engineering Results Memory reduction PPlant (without UT)PPlant (with UT) Converted triangles409 KB482 KB Primitives6.5 KB79 KB Reduction factor98 %83 %

Speed-up (1/3) Test settings: –Without any culling They would disturb our results Surely, culling algorithms would increase all frame rates –We have compared GPU primitives against triangles –Triangles rendering: Multiple VBO (Vertex Buffer Object) –GPU primitives in two situations: Exclusively Combined with unrecognized triangles –GeForce 7900

Speed-up (2/3) Triangles12.7 MΔ Unrecovered1.2 MΔ Primitives200 K

Speed-up (3/3)

Image Quality  Silhouette   Continuity   Intersection 

Conclusion Topological reverse engineering shows good efficiency –but it is restricted to CAD models (depends on regularity) With GPU primitives rendering we combine more quality, more speed and less memory Future work: new implicit GPU primitives for CAD models –GPU implementation + Rev. Eng. –Ex: half-sphere, half-ellipsoid, sheared cylinder

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