It’s been a while since CSM has been removed from THREE (R66 i guess) and we still are stuck with limited and manual shadows (directional light / sun) while it’s a requirement for scenes bigger than a single spot.
CSM is basically a LOD technique for shadows, without dealing with the actual boundary/frustum of the lights manually. The camera frustum is splitted into sections using the resolution on the actual section most effective for its boundary only, it allows automatic shadows for the entire scene, especially required for any large scenes/landscapes.
I delayed the topic myself for a while as i thought it could get restored soon, but it doesnt seem to get anytime soon. I only tested a naive geoclipping approach as experiment outside the core. I looked into the old implementation now. An old example can be seen here: http://alteredqualia.com/three/examples/webgl_road.html
I doubt it is worth just reimplementing it, since i see some issues in it, such as more far sections not properly covering the frustum (could have been not an issue back then), the seams require a smooth transition and i’m not sure if the frustums splits are made optimally. Did anyone fiddled with CSM with THREE yet? Asides of the old implementation and some sources about CSM, i’d appericate if someone has an experiment on it to quickly get to the best result.