Real-time Rendering of Dynamic Vegetation

1. Real-time Rendering of Dynamic Vegetation Alexander Kusternig Vienna University Of Technology

2. Overview • Physically based lighting • Wind Animation • Convincing pictures at high frame rates Alexander Kusternig

3. Physically based lighting

4. The difficulties of leaf rendering • Geometric complexity • Translucency and indirect lighting • Detailed microstructure

5. Leaf Rendering State of the Art • Much work done on LODs • Leaves often simplified as oriented billboards • PRT techniques • Impressive results • Create huge data sets • Static geometry Alexander Kusternig

6. Our Method [1] • Photographing leaves • Diffuse illumination • Translucency color • 3D scanning • Actual leaf geometry

7. Our Method [2] • 4 Textures per leaf side: Diffuse Color Normal HL2 Map Translucency

8. Our Method [3] • HL2 texture maps • PRT technique • To calculate translucency • The “Half Life 2” basis • Works in tangent space • Local per leaf • No costly transformation • Only 3 coefficients

9. Our Method [4] • Direct Illumination: • Cook-Torrance Specular Model • Normal Mapping • Shadow Mapping • Indirect Illumination: • Pre-baked Ambient Occlusion • Per vertex

12. Wind animation

13. Animation State of the Art [1] • Bone animation • Procedural generation • Physical models • Pre-baking key frames and interpolating • Mass spring models Alexander Kusternig

14. Animation State of the Art [2] Fastest and most flexible implementations currently used by games • Per Vertex displacement • Weights hand-painted • Many limitations exist: • Not suitable for strong wind • Only possible for trees with 1 long straight stem

15. Our Method [1] • Take best from both worlds • Physically based branch bending • Fast per vertex animation • Animation completely on the GPU • Animation data baked into vertex streams • Per-branch data baked into textures • Motion data from noise textures Alexander Kusternig

16. Our Method [2] • Computation of a branching hierarchy • Suitable for all plants • Branches calculated automatically from model • Weights propagated through hierarchy • Up to 4 levels

17. Our Method [3] • User-friendly! • Use model data from standard tree generation package (Nat FX, XFrog...) • Tweakable by adjusting a few parameters

18. Our Method [4] • Advantages: • Completely handled by GPU • Scales linearly with number of vertices • Non-linear bending of branches • Every leaf is animated individually

19. Implementation

20. Implementation [1] State of the art rendering pipeline: • DX10 • HDR pipeline • Tonemapper tuned for post-processing • Real-time illumination changes • Preetham Skylight model • Shadow mapping • Light shafts Alexander Kusternig

21. Implementation [2] Performance: • ~70000 Triangles for branches • ~12000 Leaves • >300 MB of static textures • 80-100 FPS on Geforce 8800 GTX Alexander Kusternig

22. Future Work • Sophisticated level of detail rendering • Grass rendering • Tree generation Alexander Kusternig

23. Thanks for your attention Alexander Kusternig

24. Real-time Rendering of Dynamic Vegetation Alexander Kusternig Vienna University Of Technology