/**
* Classify a point with respect to an edge, i.e. left, right of edge etc.
* @param pt :: A point as V2D
* @param edge :: A test edge object
* @returns The type of the point
*/
PointClassification classify(const V2D &pt, const PolygonEdge &edge) {
V2D p2 = pt;
const V2D &a = edge.direction();
V2D b = p2 - edge.start();
double sa = a.X() * b.Y() - b.X() * a.Y();
if (sa > 0.0) {
return OnLeft;
}
if (sa < 0.0) {
return OnRight;
}
if ((a.X() * b.X() < 0.0) || (a.Y() * b.Y() < 0.0)) {
return Behind;
}
if (a.norm() < b.norm()) {
return Beyond;
}
if (edge.start() == p2) {
return Origin;
}
if (edge.end() == p2) {
return Destination;
}
return Between;
}
/**
* Angle between this and another vector
*/
double V2D::angle(const V2D &other) const {
double ratio = this->scalar_prod(other) / (this->norm() * other.norm());
if (ratio >= 1.0) // NOTE: Due to rounding errors, if "other"
return 0.0; // is nearly the same as "this" or
else if (ratio <= -1.0) // as "-this", ratio can be slightly
return M_PI; // more than 1 in absolute value.
// That causes acos() to return NaN.
return acos(ratio);
}
