Aren't you the author of the OpenGL SuperBible? :) Welcome to OSG, woot. I bet a great deal of us own that book...
Anyways, a funny story: A few years ago when I still lived at home my grandmother saw my copy of that book and got real suspicious. She's very religious and thought that OpenGL was some kind of "cult" I was in, since the title contained the word "bible" in it. :) Funny stuff... On Mon, 2007-11-12 at 08:48 -0500, Richard S. Wright Jr. wrote: > Stephane, > > I am fairly new to OSG, but I understand your problem quite well. I > developed (and continue to maintain) a commercial solar system > simulator. The scale runs from far flung trans-neptunian objects, to > flying up and almost touching the ISS. Even without going to the > stars, you simply cannot achieve this level of detail in a single > coordinate system with OpenGL, regardless of your calculated > precision. Instead of a brute force approach, you will need to > partition your universe by scale. When flying between stars, you do > not need the same frustum as when you are orbiting a planet. When > visiting the space shuttle, you do not use the same frustum as when > drawing the planet. Render the large scale universe first (but scale > it down to smaller numbers). Then the intermediate, etc. > > I've done this myself "manually"... I would be interested in hearing > how to achieve this with OSG from other members. I imagine you will > need to create more than one scene graph and "superimpose" them. > > Richard > > On Nov 12, 2007, at 4:55 AM, Stephane Lamoliatte 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 > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
