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
