interactive ray tracing of dynamic scenes tomáš davidoviČ czech technical university
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Interactive Ray Tracing of Dynamic Scenes
Tomáš DAVIDOVIČCzech Technical University
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Three types of scenes
Static scenes Contained movement Explosions…
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Three types of scenes
Related work Havran et al.
2001 Etc????
Static scenes Build acceleration structure once Trace the structure many times
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Three types of scenes
Contained movement Build structure once Alter structure when
necessary Trace many times
Related work: Wald et al. 2007
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Three types of scenes
Explosions… Objects appear, disappear, move
wildly Cannot alter structures
Solution Rebuild every frame Use only once
References Wald et al. 2007
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What do we need?
Optimize Build + Trace time! Good structure – slow build, fast trace Poor structure – fast build, slow trace Need to find the balance
Fast build of acceleration structure Fast traversal Fast intersection Fast shading
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What do we need?
Optimize Build + Trace time! Fast build of acceleration structure
Bounding Volume Hierarchy Surface Area Heuristic approx. [Wald et
al.???] Fast traversal
Packet tracing [Wald et al. ????] Fast intersection
Vertex culling [Reshetov et al. ????] Fast shading
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BVH – SAH cost ratio
Influences: Depth of tree Triangles per
leaf
CTCI
Cost TraversalCostIntersect
Ratio = 0.1~30 tris per leaf
Depth ~20
Ratio = 1.0~3 tris per leaf
Depth ~30
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Packet traversal
Packets of rays (16x16) Uses SIMD
Traverse the tree Early hit Early miss
When in leaf Intersect triangles
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Intersection – Vertex Culling
Packet - triangle Beam plane test Triangle edge
test
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Intersection – Vertex Culling
Packet - triangle Beam plane test Triangle edge
test Standard ray-tri
test
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Packet shading
For all rays store: Hit point, view direction, normal,
material Go through all hit materials
Store Phong model coefficients Shoot light packets from light to hit
points
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Packet shading
For all rays store: Hit point, view direction, normal,
material Go through all hit materials
Store Phong model coefficients Shoot light packets from light to hit
points Compute Phong shading for the packet
Using SIMD Add color to the picture
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Models – no shading
Happy Buddha1M tris
A10218k tris
Sibenik’s Cathedral80k tris
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Ray tracing performance
less triangles
Primary rays, packets 16x16, resolution 512x512
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Build + trace performance
less triangles
Primary rays, packets 16x16, resolution 512x512
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Vertex culling speedup
Many combinations tested; packets 16x16
AB – only rays that hit leafBP – Bouding planes testNF – Triangle edge and Near Far test
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Shading “speedup”
Packets 16x16, direct illumination, no textures
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Summary and future work
Can reach 4fps for 200k tris Optimal leaf sizes
2-4 tris per leaf for Trace optimal 20-40 tris per leaf for Build + Trace
optimal Combine acceleration structures
Dynamic and static parts separated Try different acceleration structures
BIH reported to be 2.5x faster (build)
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Thank you for attentionQuestions?
Tomáš DAVIDOVIČCzech Technical University