To model the levels correctly under precomputed shadows must define objects of similar sizes approx.
The algorithm proceeds to calculate shadows is different from traditional algorithms.
Must be defined, for example, a grid of ground object to define a body of water (see picture)
Errors calculations may provide otherwise.
The shadow calculation is based in part on approximations necessary forms that allows a grouping of faces of 3D objects calculated, which allows rapid display still shadows.
Above the level with the best possible shadows.
Genrally, BSP lighting generates numerous faces to modelize shadows; Here, the shadowing modelisation is optimized.
In order to proceed about wide number of faces meshes, there is the option added that basically is drawn with stencil shadow volume.