On Mon, 2012-08-20 at 10:44 -0600, Paul Martz wrote:
> What you seem to be saying is that you want to set some OpenGL state once
> that
> applies to all contexts, and not have to set it every frame. AND, you don't
> want
> to have to add, then remove, a Camera draw callback just to make this
> happen).
> Is that a good synopsis of the issue?
It's close; I don't actually mind using a Camera draw callback for this
purpose if it's appropriate.
A real summarizing question is: under what conditions is it "safe" to
query for support of a particular extension? And what is the preferred
API for either fetching or being provided the contextID with which to do
this?
> You could keep a bool buffered_value that tells you whether or not you've set
> the initial/global state for that particular context. Initially false, then
> set
> the global state for a context and flip it to true. Would something like that
> help?
> -Paul
Certainly, but I'm still stuck on actually SETTING the state in the
first place. :)
> On 8/20/2012 10:27 AM, Jeremy Moles wrote:
> > Hello everyone! I have a bit of a strange question here, so please bear
> > with me. I'll try to be as descriptive as I possibly can, though I'm
> > certain I will misuse some terminology.
> >
> > I am adding support for the NV_path_rendering extension to
> > OpenSceneGraph. This extension adds a number of new functions to OpenGL
> > when using an NVidia card which take on the form:
> >
> > glPath{_function_}NV
> >
> > http://osgnvpr.googlecode.com
> >
> > In order to create pointers to these new extension functions, I create
> > an Extensions object in OSG using the contextID given to me during the
> > compileGLObjects method of my overridden Drawable class. This works
> > fine, and the code is running as I expect.
> >
> > https://code.google.com/p/osgnvpr/source/browse/trunk/src/PathCommands.cpp#45
> >
> > HOWEVER, this paradigm really only works when I need to call extension
> > functions associated with an instance (or instances) of my Drawable.
> > There are other functions in the NV_path_rendering API that simply set
> > global state, and it is with these functions that I'm having difficulty.
> >
> > The biggest problem here is that in order to get a pointer to the
> > Extensions static object, I need a valid GraphicsContext contextID.
> > However, I've tried a number of methods to obtain one of these, but
> > every attempt I make actually breaks the entire codebase. I wish I could
> > explain it better than that...
> >
> > For example, if I try to use some code like the following:
> >
> > ------------------------
> >
> > Windows windows;
> >
> > viewer.getWindows(window);
> >
> > cID = windows[0]->getState()->getContextID();
> >
> > osgNVPR::getNVPRExtensions(cID);
> >
> > -------------------------
> >
> > ...then I seem to get an invalid contextID and all subsequent attempts
> > to use that contextID (even by OSG itself) won't work. The entire
> > rendering process seems to be broken in this manner.
> >
> > If instead I create a Camera::DrawCallback object and use the RenderInfo
> > there instead, then everything works fine. However, I feel like I'm
> > grossly misusing a Camera::DrawCallback just to set and unset state...
> >
> > My question is: if I need to set global state like this once, somewhere
> > high in the scenegraph, what is the best way--keeping in mind that I
> > also need a valid contextID in order to access my Extensions functions
> > per-context?
> >
> > Thanks!
> >
> > _______________________________________________
> > osg-users mailing list
> > osg-users@lists.openscenegraph.org
> > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
> >
> >
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