SDSM works by rasterizing to a depth buffer on the GPU, and then using a compute shader to analyze the depth samples in order to come up with optimal projects for the shadow map splits. This can me much more accurate than using object bounding boxes, especially when consider that it will handle occlusion.
The SDSM paper demo proposes a few different technique. The simplest one is to just compute the min and max Z value visible to the camera using the depth buffer, which you can then use to compute optimal split distances. It also proposes taking things a step further by transforming every depth buffer position into the local space of the directional light, and then fitting a tight AABB per split.
MJPMember Since 29 Mar 2007
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Graphics/engine programmer for Ready At Dawn Studios
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