Hi John, The difference is small, but it can cause problems. The post draw callback is executed after the cameras scenegraph is rendered, but before any POST_RENDER camera nodes in the graph are rendered. POST_RENDER camera nodes are commonly used for 2D displays (i.e. HUD displays). If you are trying to capture a HUD with the post draw callback, it won't work. However, it should work for anything that is not inside a POST_RENDER camera. Robert added the final draw callback shortly after the OSG2.2 release after this issue was discovered. The final draw callback is called after everything in the scenegraph (including POST_RENDER cameras) is rendered. If you are trying to do screen captures, I would definitely use the final draw callback.
Also, what arguments are you passing to the image::readPixels call? You will have to pass the x, y, width, and height values from the camera viewport to this method. -Justin From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Argentieri, John-P63223 Sent: Wednesday, June 18, 2008 4:10 PM To: [EMAIL PROTECTED] Subject: Re: [osg-users] osgViewer Custom Graphics Operations Justin, I tried the exact same thing as this, but I did a setPostDrawCallback instead of setFinalDrawCallback. Do you think that could make the difference? We are doing all sorts of things with OSG that might interfere. John ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Vican, Justin E. Sent: Wednesday, June 18, 2008 4:06 PM To: OpenSceneGraph Users Subject: Re: [osg-users] osgViewer Custom Graphics Operations Hi John, I don't know what else you are trying to do, but as far as screen capturing goes, it is supported by the composite viewer. It is not explicitly supported by the osgViewer:CompositeViewer class, but it can be done through a derived osg::Camera::DrawCallback. The callback can be added to each osg::Camera in the osgViewer::CompositeViewer through the osg::Camera::setFinalDrawCallback() method. Hope this helps, Justin From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Argentieri, John-P63223 Sent: Wednesday, June 18, 2008 3:37 PM To: [EMAIL PROTECTED] Subject: [osg-users] osgViewer Custom Graphics Operations Robert/OSG, What is the plan for OSG to grant us the ability to insert custom graphics operations in a controlled order? What I mean is, what if we want to process our own application-level callbacks immediately after makeCurrent() and immediately before swapBuffers() using osgViewer::CompositeViewer? There are too many things that we can't do using osgViewer::CompositeViewer and Camera/Cull callbacks. osgViewer::CompositeViewer doesn't permit us to do image->readPixels in order to do a screen capture. I've read all your advice on the topic in this forum. It just doesn't work. We have to roll our own render loop to the point that I never even call renderTraversals(). I made my own method that substitutes that method. Of course, I don't have access to the barriers, so my viewer must be single threaded. John Argentieri
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