Chapter 7 SpeedUp Techniques

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Chapter 7Speed-Up Techniques

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Culling Techniques

• Backface and Clustered Culling
• Hierarchical View-Frustum Culling
• Portal Culling
• Detail Culling
• Occlusion Culling
• Shadow Culling

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Backface and Clustered Culling
Cross product
Dot product
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Hierarchical View-Frustum Culling
BV(Boundary Volume) Tree
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Hierarchical View-Frustum Culling
VB Tree
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Hierarchical View-Frustum Culling
Axis Aligned BSP Tree
Polygon-Aligned BSP Tree
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Portal Culling
Densely occluded architectural scene, this
algorithm was able to cull about 99 of the
geometry with a speed-up of over 100 times.
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Detail Culling

• Sacrifices quality for speed.

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Occlusion Culling
Pseudo code for a general occlusion culling
algorithm
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Occlusion Culling

• Hierarchical Z-Buffering and the Hierarchical
  Visibility Algorithm
• The HOM(Hierarchical Ocllusion map) algorithm
• Hierarchical Polygon Tilling
• Shadow Culling

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Hierarchical Z-Buffering and the Hierarchical
Visibility Algorithm
The construction of quadtree(octree)
Hierarchical Z-buffer
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Hierarchical Z-Buffering and the Hierarchical
Visibility Algorithm
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Hierarchical Polygon Tilling

• Only traverses regions of the screen where a
  polygon is visible or nearly visible.

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The HOM(Hierarchical Ocllusion map) algorithm
Occlusion map(overlap test)
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The HOM(Hierarchical Ocllusion map) algorithm
Z-depth test
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Shadow Culling
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Impostors(Sprite)

• Nailboards
• Hierarchical Image Caching

An impostor needs to be regenerated every time
Beta(tex), Beta(trans), Beta(size) is greater
than Beta(scr).
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Nailboards

• The nailboard texture image is an RGB image
  augmented with a parameter for each
  pixel, thus forming RGB Texture.
• The stores the depth deviation from the
  nailboard polygon to the correct depth of the
  geometry that the nailboard represents

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Level of Detail

• Discrete Geometry LODs
• Alpha LODs
• Geomorph LODs
• LOD management

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Discrete Geometry LODs
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Triangle Strips, Fans, and Meshes

• Strips
• Fans
• Creating Strips
• Polygon Meshes

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Strips
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Fans
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Creating Strips

• The SGI algorithm - Greedy algorithm
• The STRIPE algorithm

doubling
patchification