Although it’s possible to calculate all these shadow maps first followed by the lighting afterwards, Futuremark has decided to interleave them, which probably makes light processing a little less efficient but avoids putting excessive demands on memory space. At any given moment then, there is never more than a single shadow map in the video memory, which is partly why 3DMark 11 can still run pretty well on graphics cards equipped with just 768 MB, or even 512 MB.

As with the creation of the g-buffer, we’re talking about geometric passes here given that the whole scene must be taken into account, or at least a subset of it for the lower level CSMs. Tessellation is also used as the shadows must correspond to the objects that make them and this can represent an enormous processing load. In contrast to the pass for the creation of the g-buffer however, no colour data is calculated, only depth. Since Doom 3 and the introduction of the GeForce FXs, GPUs have been able to increase their throughput to a great extent in this simplified rendering mode.

Note this exception: objects such as vegetation, generated from false geometry, namely alpha tests, are not processed in this fast mode as pixels must then be generated so that they can be placed in the scene.