1. Rendering Forest Scenes in Real-Time EGSR 2004 Philippe Decaudin Fabrice Neyret GRAVIR/IMAG-INRIA, Grenoble, France

2. 2Rendering Forest Scenes in Real-TimeEGSR 2004 Rendering Forest Scenes in Real-Time: Previous work  Billboards  Textured quad facing camera, or cross  Widely used by applications Flight simulators, Games, … + efficiency - no parallax, popping  Simplified textured trees + parallax, 3D consistency - more expensive

3. 3Rendering Forest Scenes in Real-TimeEGSR 2004 Rendering Forest Scenes in Real-Time: Previous work  Points  Objects = distribution of discs [Levoy, Whitted - 85] [Pfister et al - SIG’00] [Rusinkiewicz et al - SIG’00] [Stamminger, Drettakis - EWR’01] [Dachsbacher et al - SIG’03] … + adaptive + adaptive - aliasing - aliasing (-) cost = 1 transformed vertex / point [Stamminger Drettakis 01]

4. 4Rendering Forest Scenes in Real-TimeEGSR 2004 Rendering Forest Scenes in Real-Time: Previous work  Volumetric textures  Volumetric densities to represent fuzzy material [Kajiya, Kay - SIG’89] [Neyret - GI’95  TVCG’98] [Meyer, Neyret - EWR’98] [Lengyel et al - EWR’01] … + few polygons, more textures + easy to filter - repetitive tiling - slicing might be visible pattern

5. 5Rendering Forest Scenes in Real-TimeEGSR 2004 Our approach  Goal:  Render dense forests  In real-time  With good visual quality  Smooth during a flyover Assumption: forests are viewed from a distance  Approach: improved real-time volumetric textures 1. Avoid pattern mapping repetition 2. Avoid view dependant artifacts 3. Adapted to the distance

6. 6Rendering Forest Scenes in Real-TimeEGSR 2004 1. Making volumetric texture aperiodic  Avoids repetitivity  Requires a set of edge-compatible patterns  Aperiodic mapping [Stam - 97] [Neyret, Cani - SIG’99] [Cohen et al - SIG’03]

7. 7Rendering Forest Scenes in Real-TimeEGSR 2004 1. Making volumetric texture aperiodic  Storing the patterns Hardware friendly + one texture + one texture + wrap + wrap + compliant with min and mag filtering + compliant with min and mag filtering v u

8. 8Rendering Forest Scenes in Real-TimeEGSR 2004 1. Making volumetric texture aperiodic  Shape of a forest pattern: a prism  We build a set of edge-compatible prisms, that we call Texcells

9. 9Rendering Forest Scenes in Real-TimeEGSR 2004 2. Our slicing scheme  Volumetric data cannot be rendered directly by GPU  Rendered using textured slices  The simplest slicing scheme:  Slices parallel to the terrain  But suffer from artifacts… Slices Terrain Texcell

10. 10Rendering Forest Scenes in Real-TimeEGSR 2004 2. Our slicing scheme  Slices parallel to the terrain : artifacts Slicing is visible at grazing angles Too transparent Too blurred  Silhouette texcells  Opacity adjustment  Anisotropic filtering  LOD

11. 11Rendering Forest Scenes in Real-TimeEGSR 2004 2. Our slicing scheme  2 kinds of texcells  Regular texcells  Sliced parallel to the ground  Set of 2D textures  Good quality and efficiency except at the silhouette  Silhouette texcells  Sliced "parallel" to the screen  3D texture  More expensive used near the landscape silhouette

12. 12Rendering Forest Scenes in Real-TimeEGSR 2004 2. Our slicing scheme: silhouette texcells  Tilting the slices  Vertices are moved vertically, no new vertices are created  Can be done by a vertex program

13. 13Rendering Forest Scenes in Real-TimeEGSR 2004 3. LOD scheme  For regular texcells  Texture set: 2D textures + MIP-map  For silhouette texcells  We fit the slicing rate to the MIP-map level of the 3D texture

14. 14Rendering Forest Scenes in Real-TimeEGSR 2004 Results  Texcells:  128 slices of 256x256 textures  12 Mb of compressed texture  20 trees / texture  Aperiodically mapped  Shading  precomputed and stored in the textures  + pseudo-shading corresponding to the lighting of the terrain

15. 15Rendering Forest Scenes in Real-TimeEGSR 2004 Results Seq #1 Seq #1  ~2300 trees  570 texcells with 4 trees/texcell  ~30 fps 640x480 (P4 1.7GHz, GeForceFX 5800) Seq #2 Seq #2  ~37000 trees  9200 texcells with 4 trees/texcell  ~20 fps 640x480 (P4 1.7GHz, GeForceFX 5800)

16. 16Rendering Forest Scenes in Real-TimeEGSR 2004 Conclusion & future work  A scheme for quality real-time volumetric textures  Coupled with an aperiodic mapping scheme  Correct filtering of the volumetric data  Full parallax effects  Well suited to represent and render dense forests  Texcells can be mixed with other representations Future work  Better culling  Dynamic lighting and shadowing [Poster at Siggraph 2004]  Maximize the use of the GPU