OpenSceneGraph

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As of October 29th 2006, FlightGear has migrated graphics functions from PLIB to OpenSceneGraph. FlightGear 1.9.0, released Decemeber 22, 2008, marked the release of the OSG version of FlightGear. PLIB is still used for network, joystick and gui functions (the latter being phased out as of 09/2012 as part of the ongoing Canvas effort). The latest version of OSG supported by FlightGear <= 3.0 is OpenSceneGraph 3.1.8 [1].

Thanks to Mathias Fröhlich and Tim Moore, we can use recent OpenSceneGraph releases.

An UML class diagram disclosing the associations between some classes of the FlightGear source code.

Downloading OpenSceneGraph

Downloading Stable OpenSceneGraph

The OpenSceneGraph project uses Subversion (SVN) to distribute their sources.

Note: The source code should not be downloaded to the build.osg directory, or the build will not work correctly. See below.

To download the latest stable version of OpenSceneGraph use:

   svn checkout http://svn.openscenegraph.org/osg/OpenSceneGraph/tags/OpenSceneGraph-3.0.1 OpenSceneGraph

Manual Download: If you don't want to use SVN, you can also pick a stable release from the OSG download page:

http://www.openscenegraph.org/projects/osg/wiki/Downloads

If the main OSG site is down (frequently) you can also use one of its various mirrors:

http://www.freebsd.org/cgi/pds.cgi?ports/graphics/osg

OpenSceneGraph developer versions

FlightGear developers may want to use a development release of OpenSceneGraph:

   svn checkout http://svn.openscenegraph.org/osg/OpenSceneGraph/tags/OpenSceneGraph-3.1.6 OpenSceneGraph

You can replace the "3.1.6" by future development OSG versions (if known to be compatible with FlightGear).

Alternatively, developers interested in today's OSG development can download the current OSG trunk.

WARNING: The sources of current OSG development aren't always compatible with FlightGear. Only use these if you're interested in OSG development or developing new OSG features for FlightGear:

   svn checkout http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk OpenSceneGraph

Compiling OpenSceneGraph

OpenSceneGraph uses cmake. Since OSG version 2.7.3 (8th Oct 2008) a relatively new version of cmake is required. According to OSGs CMakeLists.txt it's 2.6.1 but cmake 2.6.0-5 from backports.org for Debian/Etch does the trick. It's also possible to comment out lines 25 to 27 in OSGs CMakeLists.txt:

#    if(POLICY CMP0008)
#        cmake_policy(SET CMP0008 OLD)
#    endif(POLICY CMP0008)


A minimal build instruction for unix systems is

mkdir build.osg
cd build.osg
cmake ../path/to/osg/source
make
make install

On other systems the steps might be different.

Recommended options to set in the cmake menus:

  • Build type: Release
  • You don't need to build the examples, wrappers or applications.

Installing OpenSceneGraph and FlightGear with --prefix

If you use --prefix to choose were to install FlightGear and do not want to install OSG globally on the system this can be done with the following method:

OpenSceneGraph uses cmake so to build it do

 mkdir build.osg
 cd build.osg
 cmake -D CMAKE_BUILD_TYPE="Release" -D CMAKE_CXX_FLAGS_RELEASE="-O3 -pipe" -D CMAKE_C_FLAGS_RELEASE="-O3 -pipe" \
       -D CMAKE_INSTALL_PREFIX:PATH="${MY_PREFIX}" ../path/to/osg/source
 make
 make install

or if you want to avoid needing to set LD_LIBRARY_PATH

 mkdir build.osg
 cd build.osg
 cmake -D CMAKE_BUILD_TYPE="Release" -D CMAKE_CXX_FLAGS_RELEASE="-O3 -pipe" -D CMAKE_C_FLAGS_RELEASE="-O3 -pipe" \
       -D CMAKE_INSTALL_PREFIX:PATH="${MY_PREFIX}" -D CMAKE_INSTALL_RPATH_USE_LINK_PATH:BOOLEAN="true" ../path/to/osg/source
 make
 make install


Configure and build SimGear and FlightGear with --prefix as usual.

No need to install any quickly changing software globally.

Installing with --prefix is a very nice way to keep several distinct and independent versions of FlightGear around. To start a new $PREFIX directory you'll also need to install plib in it, but that is easy. Most other needed dependencies are usually available through the package system of most Linux distributions (e.g. FreeGLUT, SDL, ALSA, etc).

lib64

Content moved to Talk:OpenSceneGraph for now.

Features and issues

Regressions in CVS/HEAD

This section is meant to always remain up to date with the latest version in CVS/HEAD, please make sure to add/delete items as necessary.

  • feature to disable scenery rendering via /sim/rendering/draw-otw property is not working at the moment (11/2008)

Current issues (very out of date)

  • The 2D Panels and the rendering order of instruments ... is wrong.
  • transparency issues:
    • runway lights shine through panel:
    • runway lights shine through cloud layers in an awkward way:
    • 2D-cloud layers flood into cockpit
    • The prop of the C172 block the view on the waves of the carrier
    • The reflector gun sight on the Seahawk causes other transparent objects (carrier wake etc.) to disappear
    • A new overhead window in the C172 (inside out)
  • Runway lighting seems to have rendering artefacts on ATI Cards.
  • Enhanced runway lighting option in the drop-down menu seems to have no effect - light always appear enhanced.
  • Seneca II HSI: upper instrument clipping issue for NAV/HDG flags, heading bug, pointer


List of 'compatible' aircraft TO BE CONTINUED (NOTE: the list is out of date.)

Missing features

Due to the migration from PLIB to OSG, some of the features seen in past versions of FlightGear are now temporarily non-functional. These are:


  • 3D clouds 3D clouds back thanks to Stuart Buchanan still have some visual artifacts
  • Rendering of some scenes is not perfect.
  • Shadows
  • Exhaust shader
  • Weather Radar is not showing any clouds
  • cloud layers don't follow the curve of the earth
  • Menu Items have no effect
    • Enhanced Runway Lights
    • Bump Mapped Clouds

Miscellaneous OSG benefits

  • Models and scenery load in a separate thread
  • Tree shaders allow "forests" of trees
  • Improved precipitation modeling
  • "Pick" animations enable greater realism and ease of creation for 3D cockpits
  • Multi-monitor views

Mathias: "I think that we should make use in the longer term of the Producers capabilities for multiple view installations. But not only multipipe installs will benefit from that. The Producer will also help to get benefit from multicore SMP machines. For that the following article is of huge interest: http://www.donburns.net/OSG/Articles/OSGMP/"

Getting the PLIB Code

Use the tag PRE_OSG_PLIB_20061029 for checking out the branch with the plib scenegraph.


For SimGear, this works (more or less) as follows:


    cvs -d :pserver:cvsguest@cvs.simgear.org:/var/cvs/SimGear-0.3 login
    CVS passwd: guest
    cvs -d :pserver:cvsguest@cvs.simgear.org:/var/cvs/SimGear-0.3 co source
    cd source
    cvs up -rPRE_OSG_PLIB_20061029


For FlightGear, you have to update the "source" directory:

    cvs -d :pserver:cvsguest@cvs.flightgear.org:/var/cvs/FlightGear-0.9 login
    CVS passwd: guest
    cvs -d :pserver:cvsguest@cvs.flightgear.org:/var/cvs/FlightGear-0.9 co -rPRE_OSG_PLIB_20061029 source

The data directory should be the CVS HEAD version. Some aircraft, however, have a PRE_OSG_PLIB_20061029 branch that works better with FlightGear/plib, e.g Hawker Hunter.

External link