donkillme wrote:
> ____ ____
> |         |
> |____     |____
>      |        *|
>      |____ ____|
>       ____
>      |    |
>  ____|    |____
> | *            |
> |______________|
>  ____
> |    |
> |    |____ ____
> |           *  |
> |____ ____ ____|
>
> Hi all, the three shapes above are "concave" shapes formed by stacking
> 4 unit squares together. Given any point inside one of the boundaries
> (say, "*" in the figures above), how does one algorithmically calculate
> (or approximate) the area which is not within the line-of-sight of the
> point (i.e. blocked by the bounadry)? Thank you!!

Divide the visible region into triangles, A*B, s.t. '*' is your '*'.
The triangle-segment AB is on a boundary of your concave shape.  The
triangle segments A* and B* each intersect one or more vertices of your
concave shape.


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