Hi Stephane, I don't really understand your problem so I may say something wrong, but OSG computes matrices transforms with doubles or floats because it is the way OpenGL need them. That's why even if you use bigger numbers in your transforms, you'll need to cast them back to double for OpenGL. Or your custom transfom node will need to cut the transformations into multiple ones (which is the best solution I think to keep your scene graph like you want).
Good luck ! On Nov 12, 2007 10:55 AM, 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 > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > -- Serge Lages http://www.tharsis-software.com
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