On Mon, 2012-08-27 at 13:54 -0400, Judson Weissert wrote:
> Hello,
>
> I was hoping someone could help me with a camera manipulator/scaling
> problem that I have been having.
>
> I have a scene graph that contains geometry representing a hydraulic
> fracture. The fracture length is of the order 1000ft, the height is of
> the order 100ft, and the width is of the order .01ft. I am trying to
> appy a width exaggeration factor to the model in order to artificially
> inflate the geometry along the width axis (in my case it is along the
> z-axis). To accomplish this, I call
> osg::PositionAttitudeTransform::setScale(osg::Vec3d(1.0, 1.0, 100.0)) on
> the PAT node that I use to orient the fracture in the model. This works
> as expected, and the fracture width is exaggerated. However, the camera
> manipulator (osgGA::TrackballManipulator) does not return to the same
> home position. The larger the scale value, the further the home position
> seems to be from the model. Also, the velocity of the camera (model
> distance / screen pixel distance) when manipulated via the mouse
> increases with the scale value. That is, dragging the mouse an inch on
> the screen results in a larger camera manipulation when the scale value
> is increased.
>
> Perhaps I am making some false assumptions regarding how the camera
> manipulators and scaling operations interact? Is the scaling operation
> messing up a bounding box calculation somewhere? I tried computing then
> drawing the bounding box of the root node, but it did not seem to change
> for either case. That is, the exaggerated fracture width does not make
> the overall volume of the scene any larger (as far as I can tell).
I've been working on a custom OrthographicCameraManipulator (and have
done FirstPersonShooter and other kinds of CameraManipulators in the
past) and I've never seen this behave OTHER than how you're describing.
Scaling the PAT will definitely affect the home position of the
osgGA::StandardManipulator, so you may end up having to do something
like:
osgGA::CameraManipulator* cm = viewer.getCameraManipulator();
cm->setHomePosition(...);
That should also set autoComputeHomePosition to false, so it'll stick.
I could, of course, be misunderstanding the question. :)
> Additional information:
>
> Lib Version: OpenSceneGraph 3.1.2 (Compiled with VS2010 on Windows 7 64-bit)
> Manipulator: osgGA::TrackballManipulator
>
> Any hints/tips would be greatly appreciated.
>
> Thank you,
>
> Judson Weissert
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