24/02/1999
Gordon Müller, Dieter Fellner
1Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Hybrid Scene Structuringwith Application to Ray Tracing
Gordon Müller, Dieter Fellner
Institute of ComputerGraphics, TU Braunschweig
{gordon.mueller,d.fellner}@tu-bs.de
24/02/1999
Gordon Müller, Dieter Fellner
2Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Overview Ray Acceleration Our Algorithm
Bounding Volume Optimization Node Classification Space Subdivision
Results Conclusions
24/02/1999
Gordon Müller, Dieter Fellner
3Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Ray Accelerationprevious work
Hierarchical bounding volumes(Kay/Kajiya 1986, Goldsmith/Salmon 1987)
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Uniform space subdivision (Fujimoto et al. 1986)
Octrees, BSP-trees, … (Glassner 1984,…)
Adaptive grids, HUG (Cazals et al. 1995)
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24/02/1999
Gordon Müller, Dieter Fellner
4Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Algorithm Overview Hierarchical bounding
volume construction based on a cost function
Identification of uniform regions by classification of sub-scenes
Locally space subdivision of uniform regions
24/02/1999
Gordon Müller, Dieter Fellner
5Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Step 1:Bounding Volume Optimization Recursively subdivide the set of objects into
two disjoint sub-scenes Objects are sorted along coordinate axes No fixed subdivision position...
24/02/1999
Gordon Müller, Dieter Fellner
6Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Step 1:Bounding Volume Optimization …instead, we minimize a cost function
describing the approximated ray/scene intersection costs
Object-specific intersection costs O(n logn) on average
24/02/1999
Gordon Müller, Dieter Fellner
7Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Example (subdivision)
24/02/1999
Gordon Müller, Dieter Fellner
8Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Step 2: Node Classification Goal: detect scene nodes that are suitable base
nodes for a uniform space subdivision Recursively classify scene nodes based on
surface area of neighbor hierarchy nodes volume of neighbor hierarchy nodes average size of elementary objects below a
hierarchy node Threshold constants determined empirically
24/02/1999
Gordon Müller, Dieter Fellner
9Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Step 2: Node Classification Scene nodes hold a counter representing the
number of uniform classified sub-nodes(used in step 3)
Classification does not destroy hierarchy! O(n)
24/02/1999
Gordon Müller, Dieter Fellner
10Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Example (classification)
24/02/1999
Gordon Müller, Dieter Fellner
11Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Step 3: Uniform Space Subdivision Build uniform space subdivisions for sub-scenes
marked in the previous step Recursively subdivide the bounding box of a scene
node along the dominant axis Sub-node counter used to determine number of
voxels / subdivisions Use available bounding volume hierarchy to speed-
up voxel membership tests ! O(n) on average
24/02/1999
Gordon Müller, Dieter Fellner
12Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Timings
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BVolC
RegSub
KDTree
HUG
Hybrid
24/02/1999
Gordon Müller, Dieter Fellner
13Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Conclusions Hybrid ray acceleration
run-time efficient space efficient easy to implement easy to use
24/02/1999
Gordon Müller, Dieter Fellner
14Institute of ComputerGraphics, TU Braunschweig
Hybrid Scene Structuring with Application to Ray Tracing
Future Work Bounding volume hierarchies
View frustum/occlusion culling Dynamic environments Collision detection Parallelization
Clustering Hierarchical Radiosity