using default depth buffer in off-screen framebuffer

Question

I'm trying to implement Weighted, Blended Order-Independent Transparency

There are three passes:

1. 3D opaque surfaces to a primary framebuffer
2. 3D transparency accumulation to an off-screen framebuffer
3. 2D compositing transparency over the primary framebuffer

I need to test transparent objects against default depth buffer. I created a framebuff for transparency pass and also created a depth buffer for maybe I can copy default depth to this buffer if this is the only way. But I don't know how to do that because I created depth buffer with GL_DEPTH_COMPONENT24 but I don't know default depth format.

Is it possible to bind default framebuffer's depth buffer to another framebuffer? If not, how can I copy default depth to another depth buff, or what is best way to do this?

Answer 1

Is it possible to bind default framebuffer's depth buffer to another framebuffer?

First, you "attach" images to framebuffers. You "bind" objects to the context; you "attach" objects to other objects.

Second, no, you cannot attach images of the default framebuffer to anything.

If not, how can I copy default depth to another depth buff, or what is best way to do this?

You render to your own depth buffer entirely. Just copy/render the image data out to the default framebuffer when its time to display it.