How should I handle the issue where quaternion causes the changes in center and distance to cancel each other out in mouse-centered zooming?

[DirabloDH]

I implemented the mouse-centered zoom function using the following code, and it works fine under normal circumstances:

osgViewer::View* view = dynamic_castosgViewer::View*(&us);
if (!view) return false;

osg::Camera* camera = view->getCamera();
osg::Matrix VPW = camera->getViewMatrix() * camera->getProjectionMatrix() * camera->getViewport()->computeWindowMatrix();
osg::Matrix invVPW;
invVPW.invert(VPW);

osg::Vec3d mouse_world = osg::Vec3d(ea.getX(), ea.getY(), 0.5) * invVPW;
float scale = ea.getScrollingMotion() == osgGA::GUIEventAdapter::SCROLL_UP ? 0.9f : 1.1f;
osg::Vec3d eye, center, up;
getTransformation(eye, center, up);
osg::Vec3d look_vector = center - eye;
look_vector.normalize();
osg::Vec3d new_eye = eye + (mouse_world - eye) * (1.0 - scale);
osg::Vec3d new_center = new_eye + look_vector * (center - eye).length() * scale;
qDebug() << "new_eye" << QString("%1,%2,%3").arg(new_eye.x()).arg(new_eye.y()).arg(new_eye.z());
auto new_distance = (new_eye - new_center).length();
if (new_distance < _minimumDistance) {
return true;
}
_center = new_center;
_distance = new_distance;

However, after rotation, for instance when the quaternion values become rotation "0.167307,-0.237759,0.667011,0.685984", it leads to ineffective zooming where the distance becomes several thousand units, making it impossible to change the current view. After investigation, I found that changes in the center and distance cancel each other out, resulting in no change in the eye position.

Here is the getTransformation method:
void ViewerManipulator::getTransformation(osg::Vec3d& eye, osg::Vec3d& center, osg::Vec3d& up) const
{
osg::Vec3d offset(0.0, 0.0, _distance);
osg::Vec3d rotated = _rotation * offset;
eye = _center + rotated;
center = _center;
up = _rotation * osg::Vec3d(0., 1., 0.);
}

[xarray]

I would suggest reimplement your code in osgGA::OrbitManipulator. It should have enough virtual methods for setting zooming/rotation separately.