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?
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
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!
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