OK, if you really need to know, in your app, what is visible and what isn't, then you probably have the right approach. -Paul
> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf > Of Lars Karlsson > Sent: Friday, May 23, 2008 11:52 AM > To: osg-users > Subject: Re: [osg-users] Item buffer for lines in OSG > > Hi Paul, > > The technique used in my application is a kind of deferred shading. > I have to scan each pixel of the "item ID buffer" to detect > edges that are visible in the current frame. > > Therefore, an edge that has at least one pixel rendered into > the current frame, is deemed "visible". In the next pass, I > collect all "visible" edges into a vector<>, additionally > process vector<> for effects, and then finally render > effected lines to the color framebuffer. > > OcclusionQueryNodes? I took a look into the example, but I > can't see how this Node could return a LIST of EDGES visible > in the current frame? > > Sincerely, > Lars > > > > > > > Hi Lars -- > > > > It's not clear to me at all why you would want to do what > you describe. > > Checking every pixel in your prerender buffer seems > prohibitively expensive, > > unless we're talking about billions of vectors... Because > your app is old, > > perhaps you should consider updating its rendering algorithm to take > > advantage of more modern hardware. > > > > Is it possible for your app to programmatically identify > "heavy" portions of > > your scene graph? If so, I'd recommend parenting those > heavy subgraphs to > > OcclusionQueryNodes, which will do the occlusion test and > cull for you. > > Spatially organizing your data will help improve OSG's > opportunities for > > culling as well. > > -Paul > > > > > > > -----Original Message----- > > > From: [EMAIL PROTECTED] > > > [mailto:[EMAIL PROTECTED] On Behalf > > > Of Lars Karlsson > > > Sent: Thursday, May 22, 2008 3:45 PM > > > To: [email protected] > > > Subject: [osg-users] Item buffer for lines in OSG > > > > > > Hi, > > > > > > <apologies for a relatively long post> > > > > > > > > > I have an old OpenGL application which uses a so-called "item > > > buffer for lines". > > > This buffer is based on the idea to associate, upon loading, > > > unique IDs to all the lines in the 3D model, then (on > each frame) to: > > > > > > - render all these lines (each with a different color) into > > > this "item buffer", > > > with z-test on and lighting off (in order to preserve > > > lines' colors), > > > > > > - scan the item buffer in order to detect the lines visible > > > in the current frame. > > > (Since the line colors are unique, a line is visible if it > > > has at least > > > one pixel in this item buffer.) Finally, I > > > > > > - render these lines (visible in the current frame) into > > > the color framebuffer. > > > > > > > > > Now, since my 3D models are getting big, I decided to use > > > OpenSceneGraph 2.4 > > > in order to optimize the processing using occlusion culling, state > > > sorting and other nice features of scene graphs. > > > > > > > > > However, where to start? OSG Quick > > > Guide did not help, so any tips would be welcome. My > first idea is to: > > > > > > - write my own plugin which reads an .osg 3D model and > > > extracts the lines > > > of the model into a separate data structure, because it > > > seems that .osg > > > file format does not enforce serialization of lines > > > > > > - associate unique IDs (which are in 1-1 mapping with > unique colors) > > > to the extracted lines > > > > > > - pre-render the model (z-buffer on, lighting off, with > > > polygons in black) > > > into a osg::Camera::FRAME_BUFFER_OBJECT > > > > > > - scan each pixel of the osg::Camera::FRAME_BUFFER_OBJECT to > > > extract currently visible > > > lines, and place them into a separate vector<> > > > > > > - render this vector<> (this means that I won't use the > scene graph at > > > all for final rendering) > > > > > > > > > Any tips? > > > > > > Thanks, Lars > > > > > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-opensce negraph.org _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
