> This example doesn't show all places where the shadow is.

I'm curious. Does it not? Because, from the descriptions of how to place all the blockers in order to create a shadow on that one spot, it did seem to me as if that one spot would be the only shadow in the room.

With 16 blockers can you have more that one discrete shadow?

Have you proven there is going to be only one shadow? Is it possible there are symmetries?

I tell you that these are two different problems, just read it again:

1, given light source and an object, find position of occluders so that the object is never illuminated

and

2, given light source and occluders, find all places that are not getting illuminated,

Why are they separate problems? Maybe I should have phrased "how to create a complete shadow in a room full of mirrors".