but crytek doesn't do any preprocess for LPVs, right? so they're generating that voxel grid in real-time by deconstructing/resampling gemoetry?

Not *exactly,* no. The specific process that survived its way into Crysis 2 was to generate a reflective shadow map that described the amount of reflected light, then inject every texel from said RSM into the light propagation volume. This is specifically how global illumination was achieved, and the reason why there aren't any indirect shadows; visibility was entirely implicit. You can run a separate grid that contains information on how much light (if any) is allowed to pass through a certain voxel and use that to help propagate light more correctly, but this wasn't done in Crysis. The results can still look quite acceptable when combined with SSAO or alternate techniques that generate SH visibility directly.

EDIT: Here's the actual LPV paper.

but crytek doesn't do any preprocess for LPVs, right? so they're generating that voxel grid in real-time by deconstructing/resampling gemoetry?

Not *exactly,* no. The specific process that survived its way into Crysis 2 was to generate a reflective shadow map that described the amount of reflected light, then inject every texel from said RSM into the light propagation volume. This is specifically how global illumination was achieved, and the reason why there aren't any indirect shadows; visibility was entirely implicit. You can run a separate grid that contains information on how much light (if any) is allowed to pass through a certain voxel and use that to help propagate light more correctly, but this wasn't done in Crysis. The results can still look quite acceptable when combined with SSAO or alternate techniques that generate SH visibility directly.