Volume Rendering Hardware

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Volume Rendering Hardware

• Anselmo Lastra

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Volume Pro

• Single-chip volume renderer
• Meant for real time
• Was commercial product
• H. Pfister, J. Hardenbergh, J. Knittel, H. Lauer,
  and L. Seiler, The VolumePro Real-Time
  Ray-Casting System, Proceedings of ACM SIGGRAPH
  99, 251-260, Los Angeles, CA, August 1999

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Shear Warp Image

• Voxels read in slices

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Block Diagram

• Data read only once per frame
• 8 or 12-bit scalars
• Tri-linear interp
• Gradient block buffers 2 slices
• Classification by lookup table to RGBA
• Images sent to regular VGA card

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Chip

• Chip had 4 pipelines
• 2563, 30 Hz

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GI-Cube

• Global illumination for volumes
• Architecture paper from SUNY Stony Brook
• Frank Dachille, Arie Kaufman, GI-cube an
  architecture for volumetric global illumination
  and rendering , Graphics Hardware 2000

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Examples
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Algorithm

• Two pass
• Rays from lights to volume faces, with k
  supersamples
• These distribute energy through volume
• Rays from eye
• Rays can be transmitted, absorbed or scattered

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Machine Block Diagram
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Block Processor

• Scattering uses BRDF to change ray direction
• If simple, done on hardware if complex, sent to
  software
• I assume software means the PC, not the DSP

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Queues

• Enough queues for all blocks
• For 2563 volume with 323 block size, 128 queues
  over 4 processors
• Queue Overflow
• Rays sent to DSP
• They say this is OK because it means theres
  enough work at block processor anyway

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Queue Importance

• Pipelined insertion sorter

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Redistribution Scheme

• Works well for this volume because space is
  bounded
• Known number of bins
• Can the same thing be done for conventional ray
  tracer?

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Also

• Vizard and Vizard 2 systems from Tuebingen
• FPGA based