Hello all! Allow me to talk briefly about osgWidget's current design and
perhaps how I can change it for the better.
A number of people over the last few months have asked me why the
WindowManager object requires an osgViewer::View* to be created. This is
an interesting question, and it segues into something possibly more
complicated, and which potentially demonstrates my lack of understanding
of some things related to OSG. :)
To summarize, a WindowManager object in osgWidget is derived from
osg::Switch, and its purpose is to position and layer various Window
objects which are added to it. It does this in a kind of "virtual
space"--that is to say, it has no awareness of how it will be viewed,
and I leave that aspect up to the user. Windows in osgWidget are derived
from osg::MatrixTransform, so it is quite simple to position and size
these objects in a virtual space.
However, as I mentioned earlier, when created a WindowManager must have
access to an osgViewer::View* so that it can call the
computeInteresections() method on this pointer and perform proper
picking. This raises an interesting design question: what exactly is (or
should be) the relationship between a WindowManager and an osg::Camera?
There certainly is SOME relationship, but whether or not I am properly
utilizing it in osgWidget remains to be seen.
If any of you have used osgWidget you may be familiar with the following
convenience method:
osgWidget::WindowManager::createParentOrthoCamera()
What this member/method does is creates an orthographic 2D camera, adds
the "this" pointer as it's first child, and returns the newly created
Camera. This is a quick way to put the WindowManager object in a state
where it can be seen and behaves as expected, but I fear I may have this
all only "accidentally" working.
My question, then, is to the OSG Gurus: if you were designing osgWidget,
how would you model this relationship between the topmost osgWidget
"manager" object and the Camera to which it should be attached? Would
you use an osgViewer::View* like I do to perform picking, or would you
interface directly with the Camera and perform picking that way? If so,
the question of WindowManager->Camera relationship becomes even more
important. Furthermore, how would you handle 3D GUI objects, which can
certainly be added to a WindowManager's "virtual" space, but will appear
wildly differently depending on whether the object is viewed through an
orthographic or perspective camera?
(Please forgive me if I'm using some wrong terminology here, I hope I
get the idea across!)
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