As it was said, zpass or carmack reverse may work nicely and isn't the problem, it's the fast and correct shadow volume creation that is needed and it seems to be real tricky.
as far as I see the bottle neck of it is the calculation of the visibility of potential edge tris, because a test must be performed to see if the tris is obscured by any other tris, thus you have to check every triangle against all other triangles. That's why linepicks are so slow.
as far as I see the bottle neck of it is the calculation of the visibility of potential edge tris, because a test must be performed to see if the tris is obscured by any other tris, thus you have to check every triangle against all other triangles. That's why linepicks are so slow.