I have a problem with FBO and depth in openGL. I am passing projection, view and model matrices to a shader that writes to the g buffer. When I unbind the FBO and write to gl_FragColor the scene displays as it ought. But when I write to gl_FragData[0] then write the accompanying texture to a screen aligned quad, objects are drawn according to inverse order processed rather than depth... I can see through objects processed first to objects processed after. Has anyone had the same problem and do they know a fix? Or could someone provide syntax on reading depth values from the vertex shader, querying the current depth, then writing to the depth buffer depending on a comparison, ie, handling the operation manually in the fragment shader.