Recently I have been experimenting with using shadow maps instead of volume shadows. I was a fan of volume shadows in the past because of the sparse support on the 3D hardware. But today with 2.0 and 3.0 shaders in combination with floating-point textures, there is no reason why not to experiment. :)
All the samples i've seen and even my application seem to have significant resolution issues when dealing with lights relatively far away or when working with open environments (such as outdoors).
Although there are some papers I have seen which proposes some improvements, none really seem to find a solution which would deal well with shadow maps to represent say the shadows generated by sunlight on an outdoor scene. At least not without generating a shadow map for each shadowed object.
I am curious if anyone out there is dealing with the same situation or if they have found approaches which can aleviate some of these problems...