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<meta name="GENERATOR" content="Mozilla/4.6 [en-gb]C-CCK-MCD NetscapeOnline.co.uk (Win95; I) [Netscape]">
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2001-12-23 05:35:28 +08:00
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<title>OSG Documentation</title>
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<body text="#000000" bgcolor="#FFFFFF" link="#0000EE" vlink="#551A8B" alink="#FF0000">
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<img SRC="OpenSceneGraphBanner_Distribution.jpg" height=77 width=640>
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<h1>
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<b><i><u>Stereo</u></i></b></h1>
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The OSG has support for stereo out of the box. Currently both anaglyphic
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stereo (i.e. red/green or red/cyan glasses) and quad buffered stereo (i.e.
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active stereo using shutter glasses, or passive stereo using polarized
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projectors & glasses). It is planned to extend this support horizontal
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and vertical split window stereo implementations.
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<p>Almost all OSG applications have the potential for stereo support simply
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by setting the relevant environmental variables, or via command line arguments.
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Little or no code changes will be required, the support is handled transparently
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inside osgUtil::SceneView's handling of rendering.
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<p>If the user is planning to use head tracked stereo, or a cave then it
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is currently recommend to set it up via a VR toolkit such as <a href="http://www.vrjuggler.org">VRjuggler</a>,
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in this case refer to the VR toolkits handling of stereo, and do not invoke
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the OSG's native support, i.e. keep all the OSG's stereo specific environment
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varibles (below) set to OFF, or set the values to off within own your own
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applications.
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<br>
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<h3>
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The environmental variables of interest:</h3>
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<table CELLSPACING=5 >
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<tr>
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<td><b>OSG_STEREO</b></td>
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<td><b>ON</b></td>
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<td>turn stereo on.</td>
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</tr>
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<tr>
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<td><b>OSG_STEREO</b></td>
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<td><b>OFF</b></td>
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<td>turn stereo off (default)</td>
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</tr>
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<tr>
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<td><b>OSG_STEREO_MODE</b></td>
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<td><b>ANAGLYPHIC</b></td>
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<td>use anaglyphic stereo when in stereo (default).</td>
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</tr>
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<tr>
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<td><b>OSG_STEREO_MODE</b></td>
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<td><b>QUAD_BUFFER</b></td>
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<td>use quad buffered stereo when in stereo.</td>
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</tr>
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<tr>
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<td><b>OSG_SCREEN_DISTANCE</b></td>
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<td><b>0.50</b></td>
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<td>set the distance the viewer is from screen in metres (default shown)</td>
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</tr>
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<tr>
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<td><b>OSG_SCREEN_HEIGHT</b></td>
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<td><b>0.26</b></td>
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<td>set the height if image on the screen in metres (default shown)</td>
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</tr>
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<tr>
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<td><b>OSG_EYE_SEPERATION</b></td>
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<td><b>0.05</b></td>
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<td>set the eye seperation - interoccular distance (default shown.)</td>
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</tr>
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</table>
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<br>
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<h3>
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Command line arguments can be used to override these settings:</h3>
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<table CELLSPACING=5 >
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<tr>
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<td><b>-stereo</b></td>
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<td></td>
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<td>Switch on stereo.</td>
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</tr>
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<tr>
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<td><b>-stereo</b></td>
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<td><b>ON</b></td>
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<td>Switch on stereo.</td>
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</tr>
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<tr>
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<td><b>-stereo</b></td>
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<td><b>OFF</b></td>
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<td>Switch off stereo.</td>
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</tr>
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<tr>
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<td><b>-stereo</b></td>
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<td><b>ANAGLYPHIC</b></td>
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2001-12-23 06:30:57 +08:00
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<td>Switch on ANAGLYPHIC stereo.</td>
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</tr>
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2001-12-23 06:30:57 +08:00
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<tr>
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<td><b>-stereo</b></td>
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<td><b>QUAD_BUFFER</b></td>
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<td>Switch on QUAD_BUFFER stereo.</td>
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</tr>
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</table>
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<br>
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<h3>
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Examples:</h3>
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To invoke stereo from the comandline:
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<br><b> sgv -stereo cow.osg</b>
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<p>To invoke quad buffered stereo from the commandline:
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<br><b> sgv -stereo QUAD_BUFFER cow.osg</b>
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<p>To force all apps to start up in quad buffered stereo (if system supports
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it)
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<br><b> export OSG_STEREO=ON</b>
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<br><b> export OSG_STEREO_MODE=QUAD_BUFFER</b>
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<br><b> sgv cow.osg</b>
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<p>To set quad buffered stereo to the default, but use the commandline
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to switch stereo on:
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<br><b> export OSG_STEREO=OFF</b>
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<br><b> export OSG_STEREO_MODE=QUAD_BUFFER</b>
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<br><b> sgv -stereo cow.osg</b>
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<br>
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<h3>
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Size matters:</h3>
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For appropriate depth perception the stereo code creates separate left
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and eye views, both the frustum and modelview are shifted to account for
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the separate eye views. To achieve the right amount of adjustment
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the OSG requires the users eye separation, the distance from the eyes to
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the screen and the height of the screen. The OSG will use the defaults
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of 0.05m,0.5m and 0.26m respectively which are assumed to be reasonable
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defaults for most users workstation configurations, note the OSG_SCREEN_HEIGHT
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is the image height rather than total size of your monitor/display surface.
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For the best stereo effects please measure these values and set them up
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via the environmental variables. Once set the views you get should
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give improved depth perception. A good way of measuring how well you are
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configured for your display is to fly away from objects (using the FlightManipulator
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for instance, but not the TrackballManipulator, see below) so that they go of
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toward infinity. As they move away the offset between the two images should
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tend towards your eye separation, if you achieve this then the object will
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be perceived as at infinity.
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<br>
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<br>
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<h3>
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Camera Manipulator Modes:</h3>
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There are three osgUtil::CameraManipulator's which come with osgUtil, which
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operate as a Trackball, Drive and Flight modes of interaction (see sgv.html for
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how to invoke them in the scene graph viewer). The osgUtil::Trackball
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Manipulator automatically scales the fusion distance to that which will fusion on
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center point of rotation - this will appear at the middle of the monitor at
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the monitors depth. Whereas, the osgUtil::DriveManipualtor, osgUtil::FlightManipulator
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scale the fusion distance to the distance the viewer is from the screen, the
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results in a perception that the virtual world is scaled to physical world, this
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is clearly better for simulators and alike. You can control the fusion of
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the image in these two modes via the osg::Camera::setFusionDistanceMode(FusionDistanceMode mode)
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where mode can be osg::Camera::PROPORTIONAL_TO_LOOK_DISTANCE (used by Trackball) or
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osg::Camera::PROPORTIONAL_TO_SCREEN_DISTANCE (used by Drive and Flight),
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and osg::Camera::setFusionDistanceRatio(float). See include/osg/Camera for
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further details, and the camera manipulators for implementation details. The
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fusion distance ratio defaults to 1.0 but can be biased to move objects out or
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into screen, they will also appear to get smaller and larger respectively. The
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camera manipulators allow the user to alter this value at runtime via the '+'
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and '-' keys.
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2001-12-23 06:30:57 +08:00
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<br>
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<br>
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2001-12-23 05:35:28 +08:00
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</body>
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</html>
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