private static bool IsEar(int i, float[] xv, float[] yv, int xvLength)
{
float dx0, dy0, dx1, dy1;
if (i >= xvLength || i < 0 || xvLength < 3)
{
return false;
}
int upper = i + 1;
int lower = i - 1;
if (i == 0)
{
dx0 = xv[0] - xv[xvLength - 1];
dy0 = yv[0] - yv[xvLength - 1];
dx1 = xv[1] - xv[0];
dy1 = yv[1] - yv[0];
lower = xvLength - 1;
}
else if (i == xvLength - 1)
{
dx0 = xv[i] - xv[i - 1];
dy0 = yv[i] - yv[i - 1];
dx1 = xv[0] - xv[i];
dy1 = yv[0] - yv[i];
upper = 0;
}
else
{
dx0 = xv[i] - xv[i - 1];
dy0 = yv[i] - yv[i - 1];
dx1 = xv[i + 1] - xv[i];
dy1 = yv[i + 1] - yv[i];
}
float cross = dx0 * dy1 - dx1 * dy0;
if (cross > 0)
return false;
Triangle myTri = new Triangle(xv[i], yv[i], xv[upper], yv[upper], xv[lower], yv[lower]);
for (int j = 0; j < xvLength; ++j)
{
if (j == i || j == lower || j == upper)
continue;
if (myTri.IsInside(xv[j], yv[j]))
return false;
}
return true;
}