How to form a Concave shape out of Convex shapes?

Question

i\'m trying to get around the rule of only being able to form convex shapes in the SFML c++ library.

To do this I\'m planning on testing given vertices,

Answer 1

I assume you have your polygon as a list of point, a very simple way would be to go around your polygon and consider the sequence of triplet of consecutive points (A,B,C).

Then you just check that at one point det(AB,BC) changes its sign, where

det(AB,AC) = (x_a-x_b)(yc-yb) - (x_c-x_b)(y_a-y_b)