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<h3><img alt="" src="../sun.gif" width="100" height="98" align=
"middle"> 3-D Frames<br></h3>
<blockquote>
<p>Previous versions of DS9 would allow users to load 3-D data into
the traditional 2-D frames, and would allow users to step through
successive z-dimension pixel slices of the data cube. To visualize
the 3-D data in DS9 v. 7.0, a new module, encompassed by the new
<tt>Frame 3D</tt> option, allows users to load and view data cubes
in multiple dimensions.<br></p>
<p>The new module implements a simple ray-trace algorithm. For each
pixel on the screen, a ray is projected back into the view volume,
based on the current viewing parameters, returning a data value if
the ray intersects the FITS data cube. To determine the value
returned, there are 2 methods available, Maximum Intensity
Projection (MIP) and Average Intensity Projection (AIP). MIP
returns the maximum value encountered, AIP returns an average of
all values encountered. At this point, normal DS9 operations are
applied, such as scaling, clipping and applying a color
map.<br></p>
<p>Rendering time is independent upon the actual data cube size.
Instead, the time it takes to render is based on how many rays are
needed to project the data cube upon the screen in the view volume
and the current zoom factor. The new module requires no special
hardware or graphical processor unit (GPU) and the rendering time
is adequate for interactive GUI manipulation on most computers. The
rendering engine is developed using the POSIX thread library,
allowing multiple light weight processes to be spawned to complete
an image in parallel. The number of threads actually generated is a
user specified parameter. Since all modern hardware contain
multiple CPU cores, the default value is 8 threads. For larger work
stations, this number can be increase. For every doubling in the
number of CPU cores available, rendering times decrease
approximately 75%.<br></p>
<blockquote><tt>Example:</tt><br>
<tt># create 3d frame, load fits file</tt><br>
<tt># set view angle to az 45 el 30 deg</tt><br>
<tt># set rendering method to Average Intensity Projection</tt><br>
<br>
<tt>% ds9 -3d mycube.fits</tt> <tt>-3d vp 45 30</tt> <tt>-3d method
aip</tt><br>
<br>
<tt>% xpaset -p ds9 3d</tt><br>
<tt>% xpaset -p ds9 file mycube.fits</tt><br>
<tt>% xpaset -p ds9 3d vp 45 30</tt><br>
<tt>% xpaset -p ds9 3d method aip</tt></blockquote>
All 2-D graphics, regions, cross hairs, contours, and coordinate
grids, are applied to the current slice, which is selected by the
user. When the user wishes to match or lock a 2-D image and to a
3-D data cube, the current slice is used to determine the rendering
solution. The user can crop the data cube for all 3 axes via the
command line or the GUI. The new module also supports FITS event
files binned into a data cube.<br>
<br>
All printing support has been extended to the new 3-D module. The
user may generate 3-D images in Postscript, JPEG, TIFF, and other
formats, just as in the 2-D case. Furthermore, native printing is
supported for the Windows version.<br>
<br>
DS9 analysis macros have been enhanced to fully support the new 3-D
module, allowing the user to invoke external analysis tasks based
on the current view parameters and to return results back into DS9
in the form of text, plot, 2-D image, or 3-D image.</blockquote>
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