Passing anti-aliased output to shader - Quadro FX 3800

[johnthesoftware]

I've set up a graphics context with a fully anti-aliased scene on the left and the result of a Sobel edge-detection algorithm performed in shaders on the scene on the right of the gc. And I've just realised I'm in completely the wrong forum but I'll continue anyway just in case.

The left-hand is great, but it's clear that the edge detection, rather than being performed on the anti-aliased scene, is being done on the original non-anti-aliased output. And I think I'm about to answer my own question. Write a shader for the left scene that passes its output back to the CPU as a texture then use this as an input to the edge detection shader. Or is there way pass information between shaders maybe using the same uniform name?

When I get a result I'll report back in case anyone's interested.

John