-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Mathias Fröhlich wrote: > Hi, > > On Saturday 26 May 2007, Harald JOHNSEN wrote: >> Are we talking about the matrices used for the culling and the rendering >> ? If that's the case then we don't need precision for culling and the >> gpu does nothing with doubles, they have allready some trouble to use >> floats efficiently. > These are also the matrices that control the transform from and back to the > view. > You will get jitter if these are floats. > Remember the jittering aircraft models in earlier days ... > The workaround was a complex logic to carry that scenery center with you. > Having doubles in the transform matrices is a much simpler and cleaner > solution - without scenery center ... > > What double precision problems do you have?
Harald, You might not realize that OSG doesn't push / pop the matrix in each transform node to OpenGL. Instead, it accumulates the effective ModelView matrix for each drawable and and loads that when the drawable is rendered. This allows you to keep the coordinates of geometry as small values that comfortably fit in floats, relative to a transform that can have a very large (wgs84) translation. If the eyepoint is in wgs84 too, then the effective translation calculated by OSG won't be very large -- it's effectively limited by the visual range -- and will also fit nicely in a float. As Mathias says, this is much more convenient than a scheme where you translate all the tiles each frame relative to an eyepoint at 0. I doubt you can measure any difference between glLoadMatrixf and glLoadMatrixd. Tim -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFGWF4PeDhWHdXrDRURAnq1AKC2f7Cy70xwAwFeMFgha3PDO+NpuQCeKc7v IMwzirJnZR9C2rmxWvp7/Xs= =dW9G -----END PGP SIGNATURE----- ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
