Hi Stephane, if you can find a way in osg to keep your viewpoint at or near the origin and, instead of translating your viewpoint thru the universe, translate the universe in reverse. You will automatically get more accuracy because floating point space has highest resolution near the origin, decreasing as u go away from it.
cheers, chris On 12/11/2007, Stephane Lamoliatte <[EMAIL PROTECTED]> wrote: > Dear mister Osfield, > > I currently develop a space simulator working with very hight dynamic > range data. > During the development I met multiple floatting point number precision > problems. > > For now, I try to solve one of these that come from OpenSceneGraph : > For my scene, I need to use Matrices, Vectors and Quaternions with a > very big accuracy. (I detail an exemple of osg accuracy problem below). > I wrote a Matrixr, a matrix of real, wich is a Matrix using the GMP library. > The problem is that I can't simply replace all matrices in the code of > OpenSceneGraph by my Matrixr. > I try to change the "typedef Matrixd Matrix" by "typedef Matrixr Matrix" > in osg/Matrix, but It does not work because some class don't use the > Matrix but Matrixd or Matrixf. > Another solution would be to develop new osg::Transform and > osg::MatrixTransform using the real type and the Matrixr class. But I > don't know how to make osg considers them as transform node without > inherit them from the original osg::Transform node. > By the way, I want to know if someone have already try to do this kind > of thing, and/or if there is an accuracy node kit in development to help me. > > Best regard. > > > > > Here is a detailed example of my problem : > There is a star far far away from the center of the universe. > For some reasons I MUST have this scene graph : > [rootNode : osg::Group] -> [starTransform : osg::MatrixTransform] -> > [starModel : osg::Geode] -> ... > The Matrix in the osg::MatrixTransform is a Matrixd that contains a very > big translation vector, for example at (x=10^20, y=0, z=0) from the > center of the universe. > I want to move in the universe, close to this star at (x=10^5, y=0, z=0) > from the star and then at (x=10^20 + 10^5, y=0, z=0) from the center of > the universe. > To compute the MODELVIEW matrix, osg implicitly compute (x=10^20 + 10^5, > y=0, z=0) - (x=10^20, y=0, z=0) . > But in fact, osg works like if the camera is in the center of the > universe at (x=0, y=0, z=0). > Why ? Because osg computes matrix transforms with float and double > values. In double : 10^20 + 10^5 = 10^20. > So I can't freely move in my universe using Matrixd and that's why I > need more accuracy. > > > > -- > Lamoliatte Stephane. > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > -- http://ping.com.au http://systemic.com.au http://planet-earth.org/Rez/RezIndex.html -- It be a great secret: there be more truth at the centre. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
