problems with sharing depth buffer in FBO

[terry fun]

Hi guys,
I encounter a problem when using FBO in deferred shading system, my rendering pipeline is like this:
1) render the scene into GBuffers using MRT;
2) calculate sky lighting in screen space and output to a color texture;
3) output color texture to main frame buffer;
The problem is I wanna step 2 share depth buffer with step 1, so the calculation in step 2 only happen on pixels that is useful.
I tried create render buffer in step 1 and bind it in the FBO create in step 2 (using glFramebufferRenderbuffer), but the result is not as excepted, the depth test is not correct in step 2 and no pixel be drawn.
Anyone has done this before? or is any other way to share depth buffers among FBOs or FBO & Main FrameBuffer? any suggestion will be appreciated.

[thokra]

You don't need a renderbuffer for that. Create a depth texture and simply attach it to both FBOs. That's what I'm doing in my light pre-pass renderer and it works well(actually 3 FBOs share the same depth attachmant in my implementation).

The only thing to make sure is that the order of operations is well defined to rule out side effects.

[terry fun]

Problem found! I forget to change the depthfunc after step 2 rendering, so another frame begin with the wrong depth func and nothing draw at the beginning.
Both renderbuffer and depth texture could be used among FBOs, and thanks thokra.