1. Geometry Textures Rodrigo de Toledo, ( PhD candidate at LORIA-INRIA) (Researcher at Tecgraf, PUC-Rio) Bin Wang and Bruno Levy

2. Geometry Textures Geometry Texture is a patch of surface A set of GT is used to represent/render an entire object Representation is based on height maps Rendering is based on GPU ray casting

3. Motivation In highly detailed meshes, small triangles represent mesostructures Maybe it is better to render these mesostructres using a more appropriate representation Main idea: to use mesoscale rendering algorithms for macroscale visualization

4. Summary Motivation Scale level classification Mesoscale GPU ray-casting of height maps Conversion Visualizing Results

5. Visualization algorithms grouped into scale levels Scene-scaleMacroscaleMicroscaleMesoscale z-buffer ray tracing spatial subdivision culling object representation shading LOD impostors (between macro and micro) textures mesostructures complex lighting models photon mapping BSSRDF

6. Mesoscale Mesostructure representation –Color map –Normal map (bump) –Height map –Volumetric mesostructure –Shading function (BRDF)

7. Mesostructure visualization Expected rendering effects – – – – – Mesoscale Mesoscale methods

8. Summary Motivation Scale level classification Mesoscale GPU ray-casting of height maps Conversion Visualizing Results

9. Height-map GPU ray casting hm(x,y) missing a sample if is big ray path sampled N times P0P0 P1P1 P2P2 PiPi P i-1 v Linear search Binary search PiPi P i-1 P' i second searching step BinRayCasting() { for 1..M { Δ  Δ / 2 Δ  z(P) ? -Δ : Δ P  P + Δ’ }

10. Height-map GPU ray casting Silhouette, self-occlusion and self-shadow 6685 7055 Top view Balance: more speed Profile view Balance: more quality [Policarpo and Oliveira 2005] Balance between steps

11. It can be used to mesoscale visualization But, we propose to use it for macroscale visualization: Geometry Textures Height-map GPU ray casting

12. Geometry Textures Parallel hexahedron with height map in its interior Each one has its own orientation HM domain is not restricted to a perfect rectangle Previous work on multiple height maps: Relief Texture Mapping [OB00] Rendering Geometry with Relief Texture [BD06] Real-time VDM using per-pixel visibility [PDG05]

13. Summary Motivation Scale level classification Mesoscale GPU ray-casting of height maps Conversion Visualizing Results

14. Conversion overview Mesh PartioningBounding-boxMaps extraction Partioning Overlapping Verify folding z definition (normal median) x, y definition (PCA analysis) bbox domain in 3D color,normal,height maps extraction maps dilation Geometry Texture set mesh

15. Partitioning The most complex step in conversion Each part should not present any folding (no overhang) Domain as square as possible

16. [Steiner et al. 04] Partitioning strategies PGP VSA MethodDomain filling (%) Initial Charts Folding Charts PGP77.44%40362 VSA53.75%3976 [Ray et al. 05]

17. Summary Motivation Scale level classification Mesoscale GPU ray-casting of height maps Conversion Visualizing Results

18. Geometry Texture Results Using dragon example to test: (1.2 million triangles) Rendering quality Rendering speed Pre-processing performance Memory space

19. mesh512 2 256 2 Geometry Texture Results (rendering quality) mesh512 2 256 2 128 2 256 2 is the best option 128 2

20. Geometry Texture Results (rendering quality) Seamless reconstruction due to overlapping + z-buffer GT should respect z-buffer rules: –Compute depth + test + update z-buffer Z-fight (for the same color)

21. Geometry Texture Results (rendering performance) 256 2 GeoTex is faster than mesh for screen-size smaller than 800x600 GeForce 8800

22. Geometry Texture Results (pre-processing and memory) Original Dragon: 13.3 MB From quality point of view: 256 2 is good If memory is a problem: 128 2

23. Video

24. Conclusion Positive aspects: –Rendering speed follows a LOD behavior. –It can be used with other polygonal objects in scene (z-buffer). –Memory reduction is possible without losing too much information. Drawbacks: –Too much complex conversion algorithm. Especially the partitioning step (which is considerably elaborate). We suggest the use of multilayer height maps (FW). –It is hard to battle VBO speed in recent graphics cards. We should test GT with more complex models (such as David). If multiple models on the screen at the same time, GT can battle VBO. [PDG05]

25. Future work Image operations on geometry textures Multilayer height maps –Sequence of height maps for the entire object –Layers forming a CSG representation

26. Thank you Questions?