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HardwareAssisted CSG Rendering

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Method Overview ... Method Overview: Ray-tracing Step. Octree is traversed in ... Results comparable performance-wise to current top performing methods ... – PowerPoint PPT presentation

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Title: HardwareAssisted CSG Rendering


1
Hardware-Assisted CSG Rendering
  • Fabiano Romeiro, Luiz Velho, Luiz Henrique de
    Figueiredo

Harvard University
IMPA
IMPA
2
Motivation
  • CSG Hierarchical modeling of complex objects
  • Objects generated by boolean combinations of
    simple primitives

3
Motivation
  • Interactivity is important
  • Makes design easier
  • However it is dificult
  • Scalability

4
Previous Approaches
  • Boundary representations
  • Depth-layering (Goldfeather)
  • Recently algorithms that use GPU resources
    (Wiegand, Rappoport, Stewart, Guha, etc)
  • Blist, Depth-peeling (Hable and Rossignac)

5
Motivation
  • Recent approaches try to reach interactivity on
    ever more complex models
  • Current best performing ones are bandwidth
    limited (depth layering, depth peeling, etc)
  • GOAL
  • Make more use of GPU processing power
  • Shift bottleneck from bandwith to GPU instruction
    throughput

6
Method Overview
  • Perform spatial subdivision of the CSG object on
    the CPU until locally it is simple enough to be
    ray-traced on the GPU.
  • Locally simple enough Surface defined by a
    single primitive or boolean operation of two
    primitives

7
Method Overview Subdivision Step
  • Modified octree (sequenced kd-tree) used as
    subdivision structure

Real subdivision example
Illustrative subdivision example in 2D
8
Method Overview Subdivision Step
  • Trade-off Increasing threshold increases
    performance but introduces noticeable artifacts

9
Method Overview Ray-tracing Step
  • Octree is traversed in recursive front-to-back
    manner
  • As leaf cells are reached different action is
    taken according to cell classification

10
Method Overview Ray-tracing Step
  • As faces are rendered pixel shader runs for every
    point of the faces

b) Boolean operation of 2 primitives Shader
a) Single primitive Shader
o
o
o
o
11
Results
  • Measurements performed in 2 configurations
  • C1 Pentium-M 1.4GHz, Geforce FX Go5200
  • C2 Athlon 64 3800, Geforce 6800 GT
  • To identify bottlenecks and evaluate performance
    we measured
  • S Subdivision time (CPU)
  • TR Traversal and rendering time (GPU)
  • Ts Setup time (Bandwidth)

12
Results
CK200
CK500
CK1000
WIDGET
13
Conclusions
  • Results comparable performance-wise to current
    top performing methods
  • For models with up to 500 primitives mostly
    GPU instruction throughput limited
  • With newer GPUs, we expect our method to surpass
    other methods on such models
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