float predicate_orient2d(vector2 a, vector2 b, vector2 c)
Given 2 points a
and b
in the plane, return a positive value if c
is on the left
of the segment (a,b)
, a negative value if it is on the right of the segment, and
zero if a
, b
and c
are colinear.
More precisely, this function computes the determinant of the matrix:
[a_x a_y 1; b_x b_y 1; c_x c_y 1]
…with a guaranteed correct sign.
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