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+<!DOCTYPE doctype PUBLIC "-//w3c//dtd html 4.0 transitional//en">
+<html>
+  <head>
+    <meta http-equiv="Content-Type" content="text/html;
+      charset=ISO-8859-1">
+    <meta name="GENERATOR" content="Mozilla/4.78 [en] (X11; U; Linux
+      2.4.7-10 i686) [Netscape]">
+    <title>3D</title>
+  </head>
+  <body alink="#ff0000" bgcolor="#ffffff" link="#0000ee" text="#000000"
+    vlink="#551a8b">
+    <h3><img alt="" src="../sun.gif" align="middle" width="100"
+        height="98"> 3-D Frames<br>
+    </h3>
+    <blockquote>
+      <p>Previous versions of SAOImage 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>
+      <blockquote> </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>
+  </body>
+</html>