RT06 conference Vlastimil Havran On the Fast Construction of On the Fast Construction of Spatial Hierarchies for Ray Spatial Hierarchies for Ray Tracing Tracing Vlastimil Havran Vlastimil Havran 1,2 1,2 Robert Herzog Robert Herzog 1 Hans-Peter Seidel Hans-Peter Seidel 1 1 1 MPI Informatik MPI Informatik , , Saarbruecken, Germany Saarbruecken, Germany 2 2 Czech Technical University in Prague Czech Technical University in Prague
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On the Fast Construction of Spatial Hierarchies for Ray Tracing
On the Fast Construction of Spatial Hierarchies for Ray Tracing. Vlastimil Havran 1,2 Robert Herzog 1 Hans-Peter Seidel 1 1 MPI Informatik , Saarbruecken, Germany 2 Czech Technical University in Prague. Talk Outline. Previous work H-trees AH-trees Performance results. - PowerPoint PPT Presentation
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RT06 conference Vlastimil Havran
On the Fast Construction of Spatial On the Fast Construction of Spatial Hierarchies for Ray TracingHierarchies for Ray Tracing
Vlastimil HavranVlastimil Havran1,21,2
Robert HerzogRobert Herzog11 Hans-Peter Seidel Hans-Peter Seidel11
1 1 MPI InformatikMPI Informatik, , Saarbruecken, GermanySaarbruecken, Germany2 2 Czech Technical University in PragueCzech Technical University in Prague
RT06 conference Vlastimil Havran
Talk OutlineTalk OutlineTalk OutlineTalk Outline
• Previous work
• H-trees
• AH-trees
• Performance results
RT06 conference Vlastimil Havran
Previous WorkPrevious WorkPrevious WorkPrevious Work
RT06 conference Vlastimil Havran
Previous WorkPrevious WorkPrevious WorkPrevious Work
• Kd-trees in O(N log N)
• Bounding volume hierarchies BVH in O(N log N)
• Two-level data structures for hierarchical motion (Wald et al. 03)
• Parallel tree traversal (Szecsi et al. 03)
+ Concurrent papers this year (EGSR’06, EG’06, RT06)
RT06 conference Vlastimil Havran
Approaches to Animated ScenesApproaches to Animated ScenesApproaches to Animated ScenesApproaches to Animated Scenes
• Set of frames, planned motion or not ?
• Some objects are moving (1%, 50%, or 100%?)
Two Approaches
• Rebuild data structures from scratch for every frame
• Update data structures for new object positions
RT06 conference Vlastimil Havran
Most Objects Are Moving ….Most Objects Are Moving ….Most Objects Are Moving ….Most Objects Are Moving ….
• Rebuild from scratch? Why possibly better?
• High quality of data structures for ray tracing
• Fast rebuild from scratch is useful in general, also for larger static scenes
• Fast rebuild from scratch has not been addressed well in CG publications
• Using buckets to find out minimum of the cost (at most 100 buckets)
• Objects are put to buckets according to their centroids
• Recording also minima and maxima of object boxes in buckets
• Sweep-plane algorithm to compute tight left and right bounding boxes
RT06 conference Vlastimil Havran
Performance of Pure SKD-treesPerformance of Pure SKD-treesPerformance of Pure SKD-treesPerformance of Pure SKD-trees
• It is rather low, not competitive with kd-trees
• Low performance means: too many traversal steps and ray-object intersections
• Need for better bounding of objects
• A hybrid data structures using bounding primitives and SKD-tree nodes
RT06 conference Vlastimil Havran
How Many Bounding Volume Primitives How Many Bounding Volume Primitives in 3D ?in 3D ?How Many Bounding Volume Primitives How Many Bounding Volume Primitives in 3D ?in 3D ?
• Assumption: axis-aligned bounding planes
• In total 63 possibilities:
– 1 plane, 6 cases – corresponds to kd-tree
– 2 planes, 15 cases – we use only parallel planes (3 cases in 3D)