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

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

Physically based lighting

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

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

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

4 Textures per leaf side: Diffuse ColorNormalHL2 MapTranslucency Our Method [2]

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 8

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

Wind animation

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

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

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 15

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

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

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

Implementation

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 20

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

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

Alexander Kusternig23 Thanks for your attention

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