374 lines
25 KiB
HTML
374 lines
25 KiB
HTML
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content="text/html; charset=iso-8859-1">
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content="Mozilla/4.77 [en] (X11; U; Linux 2.4.3-20mdk i686) [Netscape]">
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<title>examples</title>
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</head>
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<body text="#000000" bgcolor="#ffffff" link="#0000ff" vlink="#990066"
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alink="#ff0000">
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<img src="images/OpenSceneGraphBanner_Distribution.jpg">
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<table>
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<tbody>
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<tr>
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<td><a href="index.html">Index</a></td>
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<td><a href="introduction.html">Introduction</a></td>
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<td><a href="contents.html">Contents</a></td>
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<td><a href="install.html">Install</a></td>
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<td><a href="dependencies.html">Dependencies</a></td>
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<td><a href="examples.html">examples</a></td>
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<td><a href="data.html">Data</a></td>
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<td><a href="osgviewer.html">Viewer</a></td>
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<td><a href="stereo.html">Stereo</a></td>
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<td><a href="osgdem.html">osgdem</a></td>
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<td><a href="plan.html">Plan</a></td>
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<td><a href="documentation.html">Reference Guides</a></td>
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</tr>
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</tbody>
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</table>
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<h2>
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<a name="Using_osgdem"></a><u>Using osgdem to generate geospatial
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terrain databases</u></h2>
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<ol>
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<li><a href="#Quick_step_by_step_guide:">Quick step by step guide</a></li>
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<li><a href="#osgdem_options">osgdem options</a></li>
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</ol>
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<hr style="width: 100%; height: 2px;">
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<h3><a name="Quick_step_by_step_guide:"></a>Quick step by step guide:</h3>
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What follows are the steps required to get osgTerrain/osgdem compiling and
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an example of how to use it to process imagery and DEM's to generate a
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paged databases.<br>
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<br>
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1) Download, compile & install GDAL. <br>
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<br>
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2) Get the latest OSG in CVS.<br>
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<br>
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3) For UNIX 'make' users, make a copy of Make/dependencies and change the
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GDAL_INSTALL entry to:<br>
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<br>
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<div style="margin-left: 40px;"><span style="font-weight: bold;">set
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GDAL_INSTALL = true </span><br>
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<span style="font-weight: bold;"></span></div>
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<span style="font-weight: bold;"><br>
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</span>Then tell the build to use your custom
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dependencies by setting the environmental variable OSG_DEPENDENCIES to
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the absolute path to your file i.e.:<br>
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<br>
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<div style="margin-left: 40px;"><span style="font-weight: bold;">export
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OSG_DEPENDENCIES=/home/billgates/my_osg_dependencies</span><br>
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</div>
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<br>
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4) Rebuild the OSG & install (if you haven't already).<br>
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<br>
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5) Oh, make sure you have a couple of GB of spare disk space, because
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you're going to need it :-) <br>
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<br>
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6) Download some data, for this example I'm using the Puget Sound data
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at: <br>
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<br>
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<a
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href="http://www.cc.gatech.edu/projects/large_models/ps.html">http://www.cc.gatech.edu/projects/large_models/ps.html
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</a><br>
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<br>
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Download Elevation Map:
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16385 × 16385 PNG: 188MB <br>
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Download Texture Map:
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16384 × 16384 PNG: 268MB <br>
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<br>
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7) To avoid aliasing artifacts when accessing data I use <a
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href="http://www.remotesensing.org/gdal/gdal_utilities.html">GDAL
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utilitiy
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programs</a> to generate overviews (basically mip maps stored in the
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.tiff format)
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via: <br>
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<br>
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<br>
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<div style="margin-left: 40px;"><span style="font-weight: bold;">gdal_translate
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ps_height_16k.png
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ps_height_16k.tif </span><br>
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<span style="font-weight: bold;">gdaladdo -r average ps_height_16k.tif
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2 4 8 16 32 </span><br style="font-weight: bold;">
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<span style="font-weight: bold;"> </span><br
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style="font-weight: bold;">
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<span style="font-weight: bold;">gdal_translate ps_texture_16k.png
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ps_texture_16k.tif </span><br style="font-weight: bold;">
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g<span style="font-weight: bold;">daladdo -r average ps_texture_16k.tif
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2 4 8 16 32 </span><br style="font-weight: bold;">
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</div>
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<span style="font-weight: bold;"> </span><br>
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<br>
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8) Now its time to run the osgdem example to generate your PagedLOD
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database, the more levels you generate the longer it will take
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(exponentially so). 'osgdem' is just a front end to osgTerrain::DataSet
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where all the hard work happens. Here's what to run : <br>
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<br>
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<div style="margin-left: 40px;"><span style="font-weight: bold;">osgdem
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--xx 10 --yy 10 -t ../ps_texture.tif \</span><br
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style="font-weight: bold;">
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<span style="font-weight: bold;">
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--xx 10 --yy 10 -d ../ps_height.tif \</span><br
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style="font-weight: bold;">
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<span style="font-weight: bold;">
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-l 8 \</span><br style="font-weight: bold;">
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<span style="font-weight: bold;">
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-v 0.1 \</span><br style="font-weight: bold;">
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<span style="font-weight: bold;">
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-o puget.ive</span><br>
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</div>
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<br>
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Then go away for lunch, afternoon and tea, as generating this much data
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takes a while... If you don't wish to wait for the full database then
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reduce the number of levels it generates by setting the -l option to a
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lower value such as 3.<br>
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<br>
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The command line options used above are: <br>
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<div style="margin-left: 40px;"> <br>
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The first part the --xx and --yy is specifying the size of the pixels
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in meters, since these png/tif don't have any geospatial data of their
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own, if you have geospatialised files then you won't need this.<br>
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<br>
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The second part -t <filename> is the option for specificing the
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texture maps to use, you can use as many times as you wish,
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osgTerrain::DataSet will moziac them into a single database. <br>
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<br>
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The third part -d is the option for specifying the digital elevation
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maps to use, as with the textures you can use as many as you like. <br>
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<br>
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The -l option specificies the maximum number of levels to generate. If
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you use a large number then the database generation will stop once the
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max resolution of your source data is matched by the resulting database.
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The database generation will decend further where there is high res
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source
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data, decend less where there is lower res data. <br>
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<br>
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The -v option specifies the scaling factor which the height is
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multiplied by.<br>
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<br>
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And finally the -o <filename> is the output format to generate the
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databases in. This will be the name of the topmost file in the one you
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should load. It can be a .ive or a .osg. The .ive is faster and has
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embedded files. <br>
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</div>
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<br>
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9) Time to play. Simply load the database in your app (make sure it
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supports the osgDB::DatabasePager - see osgsimplepager
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example for details). The standard osgviewer works just fine so,
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here goes: <br>
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<br>
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<span style="font-weight: bold;">osgviewer output.ive </span><br>
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<br>
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<br>
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10) You don't actually have to wait for osgdem to complete before you
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can browse the database, since osgdem generates
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the topmost tiles first. Its not totally robust since osgviewer can end
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up
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loading tiles that are still being written by osgdem, but it doesn't
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crash
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here under Linux, so you might be lucky too. <br>
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<br>
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11) If your imagery and DEMs have geospatial coords associated with
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them then the -xx, --yy and -v options will not be required, making
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it much simplier to specify - you just need to specifiy options such as
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<span style="font-weight: bold;">-t imge.tif</span> and -d terran.dt0
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without any need to set the coordinate system.<br>
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<br>
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12) osgdem can automatically handle mosaicing of sets of files. These
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can be specified via a sequence of <span style="font-weight: bold;">-t
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<filename></span> and <span style="font-weight: bold;">-d
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<filename></span> pairs on the commandline, or via <span
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style="font-weight: bold;">-t <directoryname></span> and <span
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style="font-weight: bold;">-d <directoryname>.</span><br>
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<br>
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<hr style="width: 100%; height: 2px;">
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<h3><a name="osgdem_options"></a>osgdem options</h3>
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There are of osgdem options to use, to list the full ranges of options
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do:<br>
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<br>
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<div style="margin-left: 40px;"><span style="font-weight: bold;">osgdem
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--help</span><br>
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</div>
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<br>
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And you should see:<br>
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<br>
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<div style="margin-left: 40px;"><br>
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<span style="font-family: monospace; font-weight: bold;">osgdem --help</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">Usage: osgdem [options] filename
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...</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">Options:</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--HEIGHT_FIELD
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Create a height field database</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--LOD
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Create a LOD'd database</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--POLYGONAL
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Create a height field database</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--PagedLOD
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Create a PagedLOD'd database</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--RGB-16
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Use 16bit RGB destination imagery</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--RGB-24
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Use 24bit RGB destination imagery</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--comment
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Added a comment/description string to</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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the top most node in the dataset</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--compressed
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Use OpenGL compression on destination</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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imagery</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> --cs <coordinates
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system string> Set the
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coordinates system of source</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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imagery, DEM or destination database.</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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The string may be any of the usual</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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GDAL/OGR forms, complete WKT, PROJ.4,</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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EPS</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--max-anisotropy
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Max anisotropy level to use when</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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texturing, defaults to 1.0.</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--max-visible-distance-of-top-level Set the
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maximum visible distance that</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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the top most tile can be viewed at</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--mip-mapping-hardware
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Use mip mapped textures, and generate</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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the mipmaps in hardware when</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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available.</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--mip-mapping-imagery
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Use mip mapped textures, and generate</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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the mipmaps in imagery.</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--no-mip-mapping
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Disable mip mapping of textures</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--radius-to-max-visible-distance-ratio Set the maximum visible
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distance ratio</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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for all tiles apart from the top most</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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tile. The maximum visuble distance is</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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computed from the ratio * tile radius.</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;"> --skirt-ratio
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<float>
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Set the ratio of skirt height to tile</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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size</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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--tile-image-size
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Set the tile maximum image size</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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--tile-terrain-size
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Set the tile maximum terrain size</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;"> --wkt <WKT
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string>
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Set the coordinates system of source</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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imagery, DEM or destination database</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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in WellKownText form.</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> --wkt-file <WKT
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file>
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Set the coordinates system of source</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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imagery, DEM or destination database</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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by as file containing WellKownText</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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definition.</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> -d
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<filename>
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Specify the digital elevation map</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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input file to process</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> -e <x> <y>
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<w>
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<h>
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Extents of the model to generate</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;"> -h or
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--help
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Display this information</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> -l
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<numOfLevels>
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Specify the number of PagedLOD levels</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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to generate</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> -m
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<filename>
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Specify the 3D database model input</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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file to process</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> -o
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<outputfile>
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Specify the output master file to</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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generate</span><br style="font-family: monospace;">
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<span style="font-family: monospace;"> -t
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<filename>
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Specify the texture map input file to</span><br
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style="font-family: monospace;">
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<span style="font-family: monospace;">
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process</span><br style="font-family: monospace;">
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<span style="font-family: monospace;">
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-v
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Set the vertical multiplier</span><br style="font-family: monospace;">
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<br style="font-family: monospace;">
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<br>
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</div>
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</body>
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</html>
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