I've got a basic cascaded shadow mapping working, but there's alot to improve. Something thats nagging me is this:
Technically, the light must have a position when rendering the shadow maps. But, it is not supposed to have one. So how do you determine what position to use when rendering depth for each of the cascade frustrums?
The way I imagine it (and do currently) is to simply offset it some amount of distance from the cameras position. It must be trickier though because this does not take geometry into account. Do you simply sum up all the geometry in each cascade to get the max height, and then offset from that? If so, how much?
Generally the resources I've found on the net simply offsets it abit from the camera, but it must be more complex than that. Any pointers on how to do this?
EDIT: another, not too unrelated question is this: how do you do culling for directional lights? do you view frustrum culling for each cascade, each frame?