The relight is tuned by moving the on-screen point ("center_light" ).

The contribution parameters can be used to mimic directional light

The shadows are faked (depth based), so for some cases it doesn't work very much. Especially for big discontinuities in depth, i.e. the shadow a character cast in front of a background. So no magic here.

BUT for selfshadowing of characters or "flat" sets it usually does the trick. Essentially it helps to fill the leaks of a simple relight. (armpits and beneath aren't supposed to catch a lot of light, aren't they ?).

The depth is supposed to be with a very small dynamic, but you can lower it by decrease the "penumbra_intensity". In fact this parameter is quite important to access decent results.

The depth is used with dark in the near and bright in the far ( but it can be inverted in the "channels section" )

By default the global_quality is set to 0.5 to avoid time consuming process (it does the calculations in half res) but set to 1, renders of course more accurate and sharps shadows.

The "output_only_shadows" can be useful when shadows placement has to be tweaked over light position.