I've been wanting to try out raymarching on real 3D scenes to implement effects like AO, soft-shadows and such.
I pretty much know how to use signed distance functions (as described by Inigo Quilez) to approximate a model and raymarch it, but I want to have way more precision and have the distance field of my scene.
How would you go about generating a (un)signed distance field from the depth buffer in screen space ? Or would the usual depth buffer be usable as a distance field (I don't think so) ? Or there might be better ways that don't use the depth buffer ?