Hi Wojciech, Thanks for your answer. I did what you suggest at my first try following an old topic about this subject. But as i had not understand why it uses a premult i changed it, thanks for explanation.
If i use this code, i get near good result, using Vec3d instead of Vec4d with homogeneous coordinates * osg::Vec3d screenCoords = _refPoint * viewMatrix * projectionMatrix * windowMatrix;* i get screen coords ( 1069, 970, 1. ) but my viewport is ( 0, 0, 1024, 768 ). The refPoint is in the view frustum so this result is not valid too :-x If i use a Vec4d to have homogeneous coordinates, i get a worth result ... i'm a bit confused. Regards, Harold 2009/9/4 Wojciech Lewandowski <[email protected]> > Hi Harold, > > OSG uses standard C arrays to store matrices. Which means these are row > major matrices. This changes order of operands. You should multiply point by > matrix not matrix by point. In your code you should rather preMultiply the > matrices. > > example: > > osg::Matrix viewMatrix = camera->getViewMatrix(); > > osg::Vec3d viewSpacePoint = worldSpacePoint * viewMatrix; > > Cheers, > Wojtek Lewandowski > > > ----- Original Message ----- > *From:* Harold Comere <[email protected]> > *To:* [email protected] > *Sent:* Friday, September 04, 2009 1:30 PM > *Subject:* [osg-users] world space to screen space & matrices > understanding > > Hi all, > > I'm trying to simply project any 3D point ,which is already in world space, > into screen space. > > I know how to do it without osg : > screen space coords = bias matrix * camera projection matrix * camera view > matrix * world space coordinates > Those coordinates are in [0, 1] range, so multiply by viewport dimensions > to get window coordinates. > > but i do not succeed doing it with osg because i m still not familiar with > it... > My current code is > > * osg::Camera * cam = _view->getCamera(); > osg::Matrix viewMatrix = cam->getViewMatrix(); > osg::Matrix projectionMatrix = cam->getProjectionMatrix(); > osg::Matrix windowMatrix = cam->getViewport()->computeWindowMatrix(); > > osg::Vec4d screenCoords = windowMatrix.postMult > (projectionMatrix.postMult (viewMatrix.postMult (_refPoint)));* > > I saw windowMatrix is the bias matrix and the viewport scale. > refPoint is a Vec4d with w = 1. ( the 3D point i want to project into > screen space ) and as operator * is not defined to multiply a Matrix with > an Vec4d, i use postMult function. > > But i dont get a valid result... what did i missed ? :-x > Thanks for your attention > > Regards, > Harold > > ------------------------------ > > _______________________________________________ > 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 > >
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