Real-time Rendering of Dynamic Vegetation

Alexander KusternigVienna University Of Technology

Overview

• Physically based lighting• Wind Animation• Convincing pictures at high frame rates

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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

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• 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 Color Normal HL2 Map Translucency

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

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• 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

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Animation State of the Art [2]

Fastest and most flexible implementationscurrently 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

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• 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

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Implementation [2]

Performance:• ~70000 Triangles for branches• ~12000 Leaves• >300 MB of static textures• 80-100 FPS on Geforce 8800 GTX

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Future Work

• Sophisticated level of detail rendering• Grass rendering• Tree generation

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Thanks foryour attention

Real-time Rendering of Dynamic Vegetation

Alexander KusternigVienna University Of Technology