public void DoRotateAroundOrigin(Vector2 mousePosition)
{
if (isRotating)
{
Quaternion activeRotationQuaternion;
if (TurntableEnabled)
{
var delta = mousePosition - rotationStartPosition;
// scale it to device units
delta /= TrackBallController.TrackBallRadius / 2;
var zRotation = Matrix4X4.CreateFromAxisAngle(Vector3.UnitZ.Transform(world.RotationMatrix), delta.X);
var screenXRotation = Matrix4X4.CreateFromAxisAngle(Vector3.UnitX, -delta.Y);
activeRotationQuaternion = new Quaternion(zRotation * screenXRotation);
}
else
{
activeRotationQuaternion = TrackBallController.GetRotationForMove(TrackBallController.ScreenCenter,
TrackBallController.TrackBallRadius,
rotationStartPosition,
mousePosition,
false);
}
rotationStartPosition = mousePosition;
world.RotateAroundPosition(mouseDownWorldPosition, activeRotationQuaternion);
Invalidate();
}
}