The Accumulation Buffer: Hardware Support for HighQuality Rendering

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The Accumulation BufferHardware Support for
High-Quality Rendering

• Paul Haeberli and Kurt Akeley
• SIGGRAPH 90

Presented by Youwei Zhang
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Objective

• Compatibility
• High-quality
• Smooth trade-off

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Introduction
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Problem of aliasing
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Contemporary workstaions

• Two observations

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Antialiasing

• Area Sampling
• Compute the fraction of pixel coverage due to
  each polygon that intersects the pixel
• Blend the fractions to obtain the final pixel
  shading
• Has problems
• Multi-Point Sampling
• multi points per pixel

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The Accumulation Buffer

• Accumulation to create antialiased images by
  rendering the scene repeatedly with sub-pixel
  offsets
• Jitter sub-pixel offset to further reduce aliasing

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Super Sampling
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Super sampled polygons
3 x 3
23 samples per pixel
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Sampling with Gaussian
Box sampling geometry
Gaussian sampling geometry
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Antialiasing quality
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Motion Blur

• Accumulate a series of discrete still images

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Depth of Field

• Integrate the light traveling along different
  paths through the aperture of the lens

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Depth of field image
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Soft Shadows

• Accumulate a series of image of different light
  sources and points on the light sources

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Do it all
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Discussion

• Other applications
• anisotropic reflection models
• filter texture maps and environment maps
• Low cost implementation
• reduce the number of bits in the drawing and the
  Accumulation Buffer

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Environment mapped image
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Conclusion

• Compatibility
• independent of all other frambuffer algorithms
• High-quality
• no practical limit to the image quality
• Smooth performance/quality trade-off
• the number of samples per pixel increase from 1