[osg-users] Improvement of Arcball Camera Handling

[Daniel Neos]

Hi,

I want to improve my CameraHandling since it acts a little bit odd if I am too far in the center of the scene, which is the lookat-point of the camera.

The camera is rotates around a specific point(mid of the boundingsphere center), always looking at it.  

But if I am getting to close to the midpoint, sometimes I lose the focus point or the camera rotates very fast. My code is rather simple, maybe there is a caveat which I am not aware of.

Also the distance changes, if I am rotating around the same axis everytime, I get close or far away.


Code:

void OsgWidgetEventHandler::rotateOrbitCamera(double angle, const osg::Vec3d& axis, osgViewer::View* viewer)
{
    const osg::Matrixd rotation = osg::Matrix::rotate(angle, axis);
    osg::Matrixd preTrans = osg::Matrix::identity();
    osg::Matrixd postTrans = osg::Matrix::identity();

    const osg::Vec3 translation = viewer->getCamera()->getViewMatrix().getTrans();
    m_rotationPoint = translation - m_boundingSphereCenter;

    preTrans.setTrans(-m_rotationPoint);
    postTrans.setTrans(m_rotationPoint);
    osg::Matrixd viewMatrix = viewer->getCamera()->getViewMatrix();
    viewMatrix = viewMatrix * (preTrans * rotation *  postTrans);
    viewer->getCamera()->setViewMatrix(viewMatrix);

    osg::Vec3d eye, center, up;
    viewer->getCamera()->getViewMatrixAsLookAt(eye, center, up);
    if (m_focusPointFlag)
    {
        viewer->getCamera()->setViewMatrixAsLookAt(eye, m_boundingSphereCenter, up);
    }
}




The m_focusPointFlag is only false when the camera was translated(not zoomed), so that the lookat point can be changed.

How can I achieve a smooth arcball camera behaviour?

Thank you!

Cheers,
Daniel

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http://forum.openscenegraph.org/viewtopic.php?p=68194#68194