PerPixel Evaluation of Parametric Surfaces on GPU

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PerPixel Evaluation of Parametric Surfaces on GPU

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stored to texture(s) Basis functions. directly provided in a fragment program ... Fetch control points from a texture - Compute basis functions. surface position ... – PowerPoint PPT presentation

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Title: PerPixel Evaluation of Parametric Surfaces on GPU

1
Per-Pixel Evaluation of Parametric Surfaces on GPU
Takashi Kanai
Yusuke Yasui
Keio University SFC
ASTOM Inc.
ACM Workshop on General Purpose Computing on
Graphics Processors Los Angeles, USA, 7-8
August, 2004
2
Per-Pixel Evaluation of Parametric Surfaces on GPU
Takashi Kanai
Yusuke Yasui
Keio University SFC
ASTOM Inc.
ACM SIGGRAPH 2004 Poster Los Angeles, USA, 8-12
August, 2004
3
Surface Rendering

In the rendering of parametric surfaces, in
general, we often use a polygon to draw the
approximation of its original surface. However,
such rendering of a polygon does not represent
its original surface exactly. This occurs notably
in the case that a polygon is coarse or that a
view position becomes closer to a surface.

4
Our Contribution

Use of GPU (Programmable Graphics Hardware)
Fragment-based evaluation (position, derivatives)
of parametric surfaces on GPU
Robust and high-quality evaluation
Interactive computation

5
Parametric Surfaces on GPU

Linear form of parametric surfaces
(Bezier, B-spline, Coons, )
Control points
stored to texture(s)
Basis functions
directly provided in a fragment
program

6
Parametric Form of Subdivision Surface Stam98
Subdivision Surface on GPU 1

u,v n,k (n subdivision level, k
domain id)
1st derivatives of both u, v directions can also
be computed

7
Implementation on GPU
Subdivision Surface on GPU 2

computed in advance
Computed for all patterns of n, k
(n 115, k 1, 2, 3. 45 patterns)
? stored in a texture
In the fragment program,
Fetch 16 control points from a texture by n, k
Basis functions
directly computed in FP
Linear combination of basis functions and control
points

8
Texture Storage
Subdivision Surface on GPU 3
9
Texture Storage (Close-up View)
Subdivision Surface on GPU 3
10
Algorithm Overview
11
Application Reflection LinesYasui and Kanai,
SMI 2004

For each fragment,
Compute a reflection vector
Compute an intersection point
Assign a color to a fragment
A line on a surface
with different color
a reflection line

12
Results
wireframe
polygon-based
fragment-based
13
Polygon-based
Pixel-based
14
Discussion

Position of a fragment
Position of parametric surface
computed on GPU
Current solution
input polygon better approximation of a surface
run fragment program with bigger size of image

15
Conclusion and Future Work

Conclusion
Fragment-based evaluation of parametric surfaces
on GPU
Robust computation
High-quality even for low polygons
Interactive computation
Future Work
The number of instruction sets in a fragment
program
1,024 (GF 5x00) ? 65,000 (GF 6x00)
Processing on a single fragment program
will be possible
(cuurrently two FPs) in the near future.

16
Contact References

Takashi Kanai
Keio University SFC
E-mail kanai_at_sfc.keio.ac.jp
Web http//www.sfc.keio.ac.jp/kanai/
References
Yusuke Yasui and Takashi Kanai,
"Surface Quality Assessment of Subdivision
Surfaces on Programmable Graphics Hardware",
Proc. International Conference on Shape Modeling
and Applications 2004 (Genova, Italy, 7-9 June
2004), pp.129-136, 2004.