Robert et al, I have been looking at an problem I have been having with the osgManipulator::RotateCylinderDragger. I have been trying to follow the code and there are a few things that stand out as questionable. Here are two issues I found with osgManipulator/src/Projector.cpp:
1. line 202,203 - Here it is trying to find a plane perpendicular to the eyeVector by taking the cross product of the cylinder axis. It doesn't correctly handle the case where the local eyeDir is parallel with axisDir. 2. line 601-606 - The computed plane intersection being calculated in 592 is being done at the edge of cylinder and the distance will always be >= the radius and therefore this code will never be hit. Likewise there is an additional check against hitCylinder here that will never be taken due to the 'if' clause on line 589. The behavior I am seeing is that a small change in mouse drag will cause a large rotation and in certain cases will also cause a rotation in the opposite direction. I haven't yet been able to determine the exact cause, but there were just some things that stuck out as odd. I am almost at the point where I am going to try replacing all of the line-cylinder intersection code with my own since it is difficult to understand/verify the algorithm. My tests have been performed on trunk using the osgmanipulator example. I have been testing both with just a RotateCylinderDragger as well as a TrackballDragger. In the case of the TrackballDragger I removed the RotateSphereDragger (_xyzDragger) to isolate the picking to just the RotateCylinderDragger(s). The specific case is trying to pick when the eyeVector is close to parallel with the major axis of the cylinder (cylinder looks like a circle). I think issue #1 is somewhat of a red herring, in that it *should* properly calculate the plane when not exactly parallel, but even in this case there is still the abnormal behavior. My findings for #2 make me question the roots of this intersection code and I wanted to get some feedback on it. Thanks in advance. Chuck Seberino _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
