[GeoLib] Check if two 3d vectors are parallel.

GeoLib/AnalyticalGeometry.cpp

@@ -55,6 +55,24 @@ Orientation getOrientation(const GeoLib::Point* p0, const GeoLib::Point* p1,
 	return getOrientation((*p0)[0], (*p0)[1], (*p1)[0], (*p1)[1], (*p2)[0], (*p2)[1]);
 }
 
+bool checkParallelism(double const*const v, double const*const w)
+{
+	// normalise
+	const double len_v(sqrt(MathLib::scpr<double,3>(v,v)));
+	const double len_w(sqrt(MathLib::scpr<double,3>(w,w)));
+
+	double coeff[3] = {
+		(v[0]*len_w) / (w[0]*len_v),
+		(v[1]*len_w) / (w[1]*len_v),
+		(v[2]*len_w) / (w[2]*len_v)
+	};
+
+	if (abs(coeff[0]-coeff[1]) < std::numeric_limits<double>::epsilon() &&
+		abs(coeff[0]-coeff[2]) < std::numeric_limits<double>::epsilon())
+		return true;
+	return false;
+}
+
 bool lineSegmentIntersect(const GeoLib::Point& a, const GeoLib::Point& b, const GeoLib::Point& c,
                           const GeoLib::Point& d, GeoLib::Point& s)
 {

GeoLib/AnalyticalGeometry.h

@@ -114,6 +114,14 @@ bool lineSegmentsIntersect (const GeoLib::Polyline* ply,
                             std::size_t &idx1,
                             GeoLib::Point& intersection_pnt);
 
+/**
+ * Check if the two vectors \f$v, w \in R^3\f$ are in parallel
+ * @param v double array of length 3
+ * @param w double array of length 3
+ * @return true if the vectors are in parallel, else false
+*/
+bool checkParallelism(double const*const v, double const*const w);
+
 /**
  * A line segment is given by its two end-points. The function checks,
  * if the two line segments (ab) and (cd) intersects. Up to now only