public static int PlanarCcw(R2Vector a, R2Vector b)
{
// Return +1 if the edge AB is CCW around the origin, etc.
double sab = (a.DotProd(b) > 0) ? -1 : 1;
var vab = a + (b * sab);
var da = a.Norm2;
var db = b.Norm2;
double sign;
if (da < db || (da == db && a < b))
{
sign = a.CrossProd(vab) * sab;
}
else
{
sign = vab.CrossProd(b);
}
if (sign > 0)
{
return(1);
}
if (sign < 0)
{
return(-1);
}
return(0);
}
public static int PlanarOrderedCcw(R2Vector a, R2Vector b, R2Vector c)
{
var sum = 0;
sum += PlanarCcw(a, b);
sum += PlanarCcw(b, c);
sum += PlanarCcw(c, a);
if (sum > 0)
{
return(1);
}
if (sum < 0)
{
return(-1);
}
return(0);
}