// calc angle between vectors A-B and C-B
// angle in range [0, pi]
@Override
public void compute() {
GeoPoint2 A = (GeoPoint2) An;
GeoPoint2 B = (GeoPoint2) Bn;
GeoPoint2 C = (GeoPoint2) Cn;
if (!A.isFinite() || !B.isFinite() || !C.isFinite()) {
angle.setUndefined(); // undefined
return;
}
// get vectors v=BA and w=BC
bx = B.inhomX;
by = B.inhomY;
vx = A.inhomX - bx;
vy = A.inhomY - by;
wx = C.inhomX - bx;
wy = C.inhomY - by;
if (Kernel.isZero(vx) && Kernel.isZero(vy) || Kernel.isZero(wx) && Kernel.isZero(wy)) {
angle.setUndefined();
return;
}
// |v| * |w| * sin(alpha) = det(v, w)
// cos(alpha) = v . w / (|v| * |w|)
// tan(alpha) = sin(alpha) / cos(alpha)
// => tan(alpha) = det(v, w) / v . w
double det = vx * wy - vy * wx;
double prod = vx * wx + vy * wy;
double value = Math.atan2(det, prod);
angle.setValue(value);
}
public final void compute() {
// Check if the points are aligned
double x1 = -A.inhomX;
double y1 = -A.inhomY;
double x2 = -B.inhomX;
double y2 = -B.inhomY;
double x3 = -C.inhomX;
double y3 = -C.inhomY;
double det = (-x2 + x3) * (y1 - y3) + (x1 - x3) * (y2 - y3);
if (Kernel.isZero(det)) {
poly.setUndefined();
} else {
ycoef[0].setValue((x3 - x2) / det);
xcoef[0].setValue((y2 - y3) / det);
constant[0].setValue(((x3 - x2) * y3 + (y2 - y3) * x3) / det);
ycoef[1].setValue((x1 - x3) / det);
xcoef[1].setValue((y3 - y1) / det);
constant[1].setValue(((x1 - x3) * y1 + (y3 - y1) * x1) / det);
ycoef[2].setValue((x2 - x1) / det);
xcoef[2].setValue((y1 - y2) / det);
constant[2].setValue(((x2 - x1) * y2 + (y1 - y2) * x2) / det);
dd.update();
poly.update();
}
}
