Hi John, An in scene graph osg::Camera is certainly the route you'd want to take, the osghud example is probably a good place to start. You can assign your own Viewport to an scene graph osg::Camera, but if you don't it'll just inherit it's parent Camera's Viewport. osg::Camera also allows you to control which of the frame buffer components to clear, if you don't want to clear anything just use camera->setClearMask(0);
Robert. On Tue, Mar 17, 2009 at 7:31 AM, John Cummings <[email protected]>wrote: > First, I'm using OSG 2.8.0 > > I'm have been porting an old application from a homegrown OpenGL > scene-graph to osg and I've come across an issue that I'm sure there is > a way to handle, but I seem to be unable to locate just the right > combination of Camera, Drawables, etc. > > While most of the old nodes are simply geometry nodes, some of them do > their own Projection before issuing geometry-type calls. I may want to > do this for a variety of reasons, including allowing finer grained > control of the depth buffer or simply covering over something that has > already been drawn. In my old OpenGL code, the render method for one of > these problem nodes may look something like: > > void MyNode::Render() > { > glMatrixMode(GL_PROJECTION); > glPushMatrix(); > glLoadIdentity(); > > // Then either: > glOrtho (...); > // or > gluPerspective(...); > // or > glFrustrum(); > > glMatrixMode(GL_MODELVIEW); > > // begin, end, etc. > > glMatrixMode(GL_PROJECTION); > glPopMatrix(); > glMatrixMode(GL_MODELVIEW); > > RenderChildren(); > } > > I've played with the Camera node and "NESTED_RENDER" seemed from its > name to be what I wanted. That is, I though I could simply attach an > osg::Camera node anywhere in my scene graph and it would act much like > my nodes above. I either didn't set the correct options or this is not a > valid use of the Camera class. > > I've also tried attaching a camera to the root node (more properly I am > attaching it to the Scene data for my view). That works great for things > like a HUD, but that doesn't quite seem right in this particular case. > For what it's worth "this particular case" is where I would like to put > a viewport size quad over the viewport, which would cover effectively > cover up my ancestors but allow my children to be seen (I also thought > an osg::Billboard is what I might want, but that didn't seem to be right > either). However, I've also wanted to do this same thing for sky > effects, etc. but have found clunky workarounds for most of the other > cases. > > I then got to looking at the Drawable class and thought that overloading > drawImplementation would be the best thing to do. However, that doesn't > seem quite right. Perhaps it is after all. > > So, I'm sure that I can do this in osg, I'm just not sure how. I'm still > adjust my mind to the osg paradigm, so I've probably overlooked > something obvious, although I didn't see it when I search the mailing > list. In essence, I want to be able to do the same type of inline > projection I did before. What am I missing? > > Thank you > John Cummings > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org >
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