Rendering Forest Scenes in RealTime

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

• EGSR 2004

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Rendering Forest Scenes in Real-TimePrevious
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

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Rendering Forest Scenes in Real-TimePrevious
work

• Points
• Objects distribution of discs
• Levoy, Whitted - 85
• Pfister et al - SIG00 Rusinkiewicz et al -
  SIG00
• Stamminger, Drettakis - EWR01 Dachsbacher
  et al - SIG03
• adaptive
• - aliasing
• (-) cost 1 transformed vertex / point

Stamminger Drettakis 01
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Rendering Forest Scenes in Real-TimePrevious
work

• Volumetric textures
• Volumetric densities to represent fuzzy material
• Kajiya, Kay - SIG89
• Neyret - GI95?TVCG98
• Meyer, Neyret - EWR98
• Lengyel et al - EWR01
• few polygons, more textures
• easy to filter
• - repetitive tiling
• - slicing might be visible

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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
• Avoid pattern mapping repetition
• Avoid view dependant artifacts
• Adapted to the distance

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1. Making volumetric texture aperiodic

• Aperiodic mapping

• Avoids repetitivity
• Requires a set of edge-compatible patterns

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1. Making volumetric texture aperiodic

• Storing the patterns

Hardware friendly one texture wrap
compliant withmin and mag filtering
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1. Making volumetric texture aperiodic

• Shape of a forest pattern a prism
• We build a set of edge-compatible prisms,
• that we call Texcells

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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

Texcell
Slices
Terrain
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2. Our slicing scheme

• Slices parallel to the terrain artifacts

? Silhouette texcells
? Anisotropic filtering
? Opacity adjustment
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2. Our slicing scheme

• 2 kinds of texcells

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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

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3. LOD scheme

• For silhouette texcells
• We fit the slicing rate to the MIP-map level of
  the 3D texture

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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

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Results
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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