Terrain rendering in games

1
Terrain rendering in games

• Matej Mlejnek
• Institute of Computer Graphics and Algorithms
• Vienna University of Technology
• Vienna / Austria

2
Outline

• overview of terrain algorithms
• optimization criteria
• Lindstrom algorithm
• progressive meshes
• ROAM
• performance enhancements
• games and engines

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Overview of terrain algorithms (1)

• grid vs. TIN

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Overview of terrain algorithms (2)

• discrete LOD
• Continuous LOD
• grid-based
• continuous LOD rendering by Lindstrom
• Real-time Optimally Adapting Meshes (ROAM)
• TIN-based
• progressive meshes

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Optimization criteria

• time required to achieve a given triangle count
• user specified view-dependent metrics
• simplicity
• strict frame rates
• dynamic terrain
• continuous changes
• etc.

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Continuous LOD by Lindstrom (1)

• Quad tree
• bottom-up
• block-basedvs.vertex-based

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Progressive meshes

• PM representation
• only single operationmerge (edge
  collapse)split (vertex split)
• view-dependent PM

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ROAM (1)

• triangle bintree
• top-downalgorithm
• 2 priority queues
• merge
• split

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ROAM (2)

• (mergeable) diamond
• forced split gt
• no effort to avoiddiscontinuities

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Comparison
Lindstrom ROAM PM
elementary operation complex,1 vertex reduction basic,1 vertex reduction complex,2 vertices reduction
triangles rigth-isosceles rigth-isosceles introduces slivers
complexity O(mesh size) O(triangle changes) O(mesh size)
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Performance enhancements

• backface culling
• object positioning
• atmospheric obscurance
• view frustum culling
• progressive optimization

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Games and engines

• NetImmerse
• (progressive
• meshes)

Tribes (Lindstrom algorithm)
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Results

• Hoppe progressive meshes

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Thank you!
Matej Mlejnek matej.mlejnek_at_cg.tuwien.ac.at