OSG's Trackball manipulator (and other core OSG manipulators) set the
modelview matrix so that +Z is up. If you'd like to use +Y up, you'll
need to derive a new manipulator.
BTW, I think this is covered in the online FAQ as well as the Quick
Start Guide.
-Paul
On May 30, 2008, at 8:21 AM, Poirier, Guillaume wrote:
Hello,
I am trying to represent a trackball view with a cube, with each
face of the cube labelled "front", "top",
"right", etc. I'd like the cube to be positioned in the window
corner and follow the trackball view. I
assume that the initial home position corresponds to the front view.
Now I've been playing with this for
a while and I am getting confused with transformations :(
I create the cube as follows:
m_pFaceFront = osg::createTexturedQuadGeometry(osg::Vec3(-0.5,
-0.5, -0.5),osg::Vec3(1,0,0),osg::Vec3(0,0,1));
m_pFaceBack = osg::createTexturedQuadGeometry(osg::Vec3(0.5, 0.5,
-0.5),osg::Vec3(-1,0,0),osg::Vec3(0,0,1));
m_pFaceLeft = osg::createTexturedQuadGeometry(osg::Vec3(-0.5, 0.5,
-0.5),osg::Vec3(0,-1,0),osg::Vec3(0,0,1));
m_pFaceRight = osg::createTexturedQuadGeometry(osg::Vec3(0.5, -0.5,
-0.5),osg::Vec3(0,1,0),osg::Vec3(0,0,1));
m_pFaceTop = osg::createTexturedQuadGeometry(osg::Vec3(-0.5,
-0.5, 0.5),osg::Vec3(1,0,0),osg::Vec3(0,1,0));
m_pFaceBottom = osg::createTexturedQuadGeometry(osg::Vec3(-0.5, 0.5,
-0.5),osg::Vec3(1,0,0),osg::Vec3(0,-1,0));
So I believe that the "front" is facing -Y, "top" +Z, and "right" +X.
I place the cube under a camera with absolute reference frame and
set the view to identity. I am thinking the
view frame has +X to the right, +Y up, and +Z out of the screen.
What I see is the bottom face upside down.
I would have expected to see the top face so I am not entirely sure
what is going on...
My second question is how to make the cube follow the trackball
view. The cube has a matrix transform as a parent
and I set its rotation in an update callback as follows:
osg::Matrixd invMat;
invMat = m_pViewCube->GetView()->getCameraManipulator()-
>getInverseMatrix();
osg::Matrixd rotMat;
rotMat.setRotate(invMat.getRotate());
m_pViewCube->GetTransform()->setMatrix(rotMat);
The cube rotation is "inverted" wrt to the trackball when using the
inverse matrix. Using the manipulator matrix
instead of its inverse, the cube follows correctly on drag
vertically but has the wrong rotation axis on drag horizontally...
Any help with this would be greatly appreciated !
bill
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