Hi, Sebastian You can setup blend func in a way that will keep old rgb values and replace alpha with new value. for second pass -> BlendFunc(osg::BlendFunc::ZERO, osg::BlendFunc::ONE, osg::BlendFunc::ONE, osg::BlendFunc::ZERO). However if you reading from same texture attached to camera output this is not gonna work, unless you use NV_texture_barrier extension (and it have limitations too).
Cheers 22.09.2011, 11:46, "Sebastian Messerschmidt" <[email protected]>: > Thanks to all replies but I was able to figure it out. > > My initial idea was to modify a color attachment created in the first > pass in the second pass only where fragments were created(i.e. depth was > written) > I came up with the following solution: > > 1. Pass > RTT-Cam1 > - DEPTH, COLOR1, COLOR2, ... > - renders the scene > 2. Pass > RTT-Cam2 > - DEPTH, COLOR1 (same attachments as in the first pass > - depth test to GREATER > - depth writes off > - disable color and depth clearing (which we want to reuse) > - bind the COLOR1-texture as uniform input > - render a full screen quad with camera in ABSOLUTE_RF and same > viewport as first pass > - in the frag shader for instance do: gl_FragData[0]= > vec4(texture2D(firstPassTexture,gl_TexCoord[0].st).rgb, 0.0) + > vec4(0.0,0.0,0.0, myNewTerm); > > This works, because the fullscreen quad rendered will pass depth test > only if something was written there in the first pass. Using this sceme > saves us a stencil test. > > There is a remaining question however: > What I really wanted to do is to write the gl_FragData[0].rgb in the > first and gl_FragData[0].a in the second pass. > This gave me a blank result (with the alpha component set to 1) > Do I have to enable blending or something? Or is it illegal to write > uncomplete FragData? > >> Hello, >> >> I've have a question regarding RenderToTexture in a multipass setup. >> I have to RTT cameras, the first one has DEPTH and 3 color >> attachments, while the second has only one color attachment. >> I need to use the data from the first RTT-pass in the second camera, >> so the renderorder is set accordingly. >> >> Basically my scene is organized like this: >> >> root >> | >> RTTCamera_1 >> | |----Model >> RTTCamera_2 >> | |----Model >> >> Booth cameras use the same geometry, viewport, transform. Yet the >> Model graph is culled twice. >> Is there any way to prevent the second cull traversal? I.e. reuse the >> batch collected in the first culling? >> >> cheers >> Sebastian >> _______________________________________________ >> osg-users mailing list >> [email protected] >> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
