vizard ii: a reconfigurable interactive volume rendering system wsi / gris, universität tübingen...
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VIZARD II: VIZARD II: A Reconfigurable Interactive A Reconfigurable Interactive Volume Rendering SystemVolume Rendering System
WSI / GRIS, Universität Tübingen
‡Philips Research, Hamburg
†Viatronix
*ATI
M. Meißner†, U. Kanus, G. Wetekam, J. Hirche, A. Ehlert, W. Straßer,
M. Doggett*, P. Forthmann‡, and R. Proksa‡
WSI/GRIS, University of Tübingen
09/02/2002
OverviewOverview
• Motivation
• Features
• System
• RPU
• Results & Future Work
• Acknowledgments
WSI/GRIS, University of Tübingen
09/02/2002
MotivationMotivation
Need for interactive frame rates, the highest possible image quality, interactive change of parameters, and different rendering modes.
Learn from PC graphics (& from keynote):
Software (CPU) scales only with Moore’s Law but hardware can additionally scale by implementing the full algorithm (pipeline) in hardware and possibly parallel pipelines (SIMD)
WSI/GRIS, University of Tübingen
09/02/2002
MotivationMotivation
However, hardware (ASIC) is expensive, pays out only for large quantities, and change/ adaption in design requires new fabrication.
Thus, combine the performance of special purpose hardware with (almost) the flexibility of a software solution using reconfigurable logic (FPGA).
Board can be re-used for other applications, e.g. volume reconstruction (Philips)
WSI/GRIS, University of Tübingen
09/02/2002
OverviewOverview
• Motivation
• Features
• System
• RPU
• Results & Future Work
• Acknowledgments
WSI/GRIS, University of Tübingen
09/02/2002
FeaturesFeatures
Rays are cast from viewplane:
• Flexible sampling rate• Trilinear interpolation• Post-classification• Per sample Phong shading• High precision compositing
Acceleration Techniques:
• Geometry based space leaping• Early ray termination
WSI/GRIS, University of Tübingen
09/02/2002
FeaturesFeatures
Ensure high(est) image quality by:
• unlimited ray-casting including parallel and perspective projections
• complex gradient filters mandatory for correct GM ( gradient as per voxel property)
Left: Original volume rendering Right: Central difference, GM (>1), result depends on object orientation due to non symmetric gradient filter
WSI/GRIS, University of Tübingen
09/02/2002
FeaturesFeatures
Ensure high(est) image quality by:
• full classification with material properties on a per sample base
• additional interval based classification mode
(pre-integration) and accurate combination
with Phong shading [Meissner et al. GI2002]
WSI/GRIS, University of Tübingen
09/02/2002
OverviewOverview
• Motivation
• Features
• System
• RPU
• Results & Future Work
• Acknowledgments
WSI/GRIS, University of Tübingen
09/02/2002
SystemSystem
Memory interface:
• Trilinear interpolation requires eight Voxels in parallel. Ideally, one would like to have eight memory devices
• For more flexibility, use exchangeable DIMMs
instead of single SDRAM devices
• DIMM modules are large in physical size and come in 64 data bits, thus use four – eight would not fit anyway - and store two voxel values (32 bit each) in one entry.
WSI/GRIS, University of Tübingen
09/02/2002
Cubic memory organization: Volume is partitioned in sub-cubes and stored in linear memory (4 DIMMs, 64 bit)
DIMM0
DIMM1
DIMM2
DIMM3
32x32x32 Voxel fit into Caches of 4 DIMMs --> ideal access time (e.g. 10ns)
SystemSystem
Replication
WSI/GRIS, University of Tübingen
09/02/2002
Non blocking access using prefetching:
Delay of page x-ings can be overlapped in time. [Doggett et al. HWW1999]
Time
No
Yes
SystemSystem
WSI/GRIS, University of Tübingen
09/02/2002
PCI Interfac
e
System bus
PCI bus
Ray casting
DIMMXilinx
Virtex
SRAM
PCI card (long!)
SystemSystem
DSP
SDRAM
Ray Setup
Host
com
pu
ter
WSI/GRIS, University of Tübingen
09/02/2002
DIMMs
Reconfigurable chip (FPGA)DSP
PCI interface chip
Power supplyand converters
SRAM
SystemSystem
WSI/GRIS, University of Tübingen
09/02/2002
OverviewOverview
• Motivation
• Features
• System
• RPU
• Results & Future Work
• Acknowledgments
WSI/GRIS, University of Tübingen
09/02/2002
RC
RPU
Central unit of VIZARD II is the RPU:
AU
DIMMs
TIU
SU
bandwidth iscritical
RPURPU
CU
SRAMs
Com
bin
e
BU
High frequency is challenging
Sample props /pre-integration
WSI/GRIS, University of Tübingen
09/02/2002
Compositing @ 100 MHz is a challenge:
Opacity: Ai+1 = Ai + (1-Ai) * As
Inverse, multiply and subsequent Add of two 16 bit values is not feasible in 10ns
Use Threading: One compositing unit, multiple processed rays
[Hesser VG ’99]
RPU: CompositingRPU: Compositing
WSI/GRIS, University of Tübingen
09/02/2002
Iteratively process n rays instead of one:
>= Eight rays allow frequency of 100 MHz
+ Better memory efficiency (overall less page x-ings)
+ Higher efficiency of early ray termination(overall pipeline latency is “divided” by number of rays)
Use early ray group termination
RPU: CompositingRPU: Compositing
RC BU
WSI/GRIS, University of Tübingen
09/02/2002
OverviewOverview
• Motivation
• Features
• System
• RPU
• Results & Future Work
• Acknowledgments
WSI/GRIS, University of Tübingen
09/02/2002
ResultsResults
Physical Design (~2 million gates)
Memory-Controller(s)
CU & SU BU
RC & AU TIU
DS
P-I
/O
WSI/GRIS, University of Tübingen
09/02/2002
ResultsResults
WSI/GRIS, University of Tübingen
09/02/2002
ResultsResults
DEMO
WSI/GRIS, University of Tübingen
09/02/2002
ResultsResults
VIZARDII VolumePro TexMap
Pipelines,@MHz 1@50 4@250 4@300
Speed 3-7 >= 30 <=10
Perspective yes (no) (yes)
Precision 16 12 8-10
iso-surface yes no (yes)
Pre-integrated yes no (yes)
ERT & Co yes yes (no)
WSI/GRIS, University of Tübingen
09/02/2002
ResultsResults
Flexibility: Dual use of the same board!!!
Philips Research developed a design for volume reconstruction from projected images (C-arm CT, currently at 50 MHz)
1. Reconstruction in 1 min (SW > 30 min)
2. Subsequently interactive volume rendering of reconstructed data
WSI/GRIS, University of Tübingen
09/02/2002
Future WorkFuture Work
On-chip ray setup: Remove current bottleneck of system
Space Leaping: “Content based” real-time check of
contributing 163 subcubes (50x per second) [Meissner et al. VG2001]
Non-photorealistic rendering: Technical drawings
WSI/GRIS, University of Tübingen
09/02/2002
OverviewOverview
• Motivation
• Features
• System
• RPU
• Results & Future Work
• Acknowledgments
WSI/GRIS, University of Tübingen
09/02/2002
AcknowledgementsAcknowledgements
Work:
•Fellows and many many students
Funding:
•German Research Council (DFG), grant 382
WSI/GRIS, University of Tübingen
09/02/2002
ConclusionConclusion
Graphics
Hardware
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