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AHPCRC Graphics Strategy
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The raster tools 'bob' and 'raz' are used at the AHPCRC at the tail
end of the visualization process to view processed 2D and 3D data
fields as fast as possible.

Typically the user will have first calculated the viewing parameter
desired from the raw simulation variables, and if necessary recast the
data onto a regular grid.  This regularized data is then scaled into
the range 0-255, and a single byte is written for each value.  These
steps are often performed by the user using a custom program, or
lately using a modular visualization package such as SGI Explorer.

At this stage the user will have hundreds or thousands of 2D or 3D
raster files, one file for each time step.  To date the 2D data files
have ranged in size up to 2048 by 2048, and 3D data files have ranged
up to 512 by 512 by 512.  In order to make working with these
multi-gigabyte data sets practical, the AHPCRC graphics lab maintains
a 50 GB disk farm distributed between three SGI power series
workstations.  The file systems, 7.5GB in size, are striped over
two or four disks.

In the case of 2D data the user might use the Utah Raster Toolkit
(substitute your favorite toolkit here) to annotate and combine
images.

In the 3D case the user runs 'bob' to browse the data bricks and
perhaps generate a movie sequence.  In effect this stage reduces the
data set from 3D raster to 2D raster.

Finally, 'xraz' is used to stream 2D raster data from disk to screen.
'xraz' is the X window front end to 'raz', which is script driven.
'raz' loads files onto the raw disk partitions or into memory, and
then streams the raster to the frame buffer.  At the AHPCRC several
striped disk partitions are kept open, with no file system on them,
for 2D and 3D raster streaming.  Using fast drives we have been able
to stream at 13 MB/sec from disk to screen.

Both 'bob' and 'raz' have parameters like "blocksize" for use with 
raw disk partitions.

For more information on adding fast disk drives to the SGI Iris,
contact Tom Ruwart at tmr@ahpcrc.umn.edu.

