How to determine if a point is in a 2D triangle? [closed]

Answer 1

bool point2Dtriangle(double e,double f, double a,double b,double c, double g,double h,double i, double v, double w){
    /* inputs: e=point.x, f=point.y
               a=triangle.Ax, b=triangle.Bx, c=triangle.Cx 
               g=triangle.Ay, h=triangle.By, i=triangle.Cy */
    v = 1 - (f * (b - c) + h * (c - e) + i * (e - b)) / (g * (b - c) + h * (c - a) + i * (a - b));
    w = (f * (a - b) + g * (b - e) + h * (e - a)) / (g * (b - c) + h * (c - a) + i * (a - b));
    if (*v > -0.0 && *v < 1.0000001 && *w > -0.0 && *w < *v) return true;//is inside
    else return false;//is outside
    return 0;
} 

almost perfect Cartesian coordinates converted from barycentric are exported within *v (x) and *w (y) doubles. Both export doubles should have a * char before in every case, likely: *v and *w Code can be used for the other triangle of a quadrangle too. Hereby signed wrote only triangle abc from the clockwise abcd quad.

A---B
|..\\.o|  
|....\\.| 
D---C 

the o point is inside ABC triangle for testing with with second triangle call this function CDA direction, and results should be correct after *v=1-*v; and *w=1-*w; for the quadrangle