X-Git-Url: http://shamusworld.gotdns.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fgeometry.cpp;h=95d12c65068b16715086191e1d70c7e01483dcbd;hb=bf5a50feb0f84a4627a65c5b82c3ca2d2eefe54b;hp=4cd229f76da7967d10811ed3ff803a0d46427e92;hpb=c20f82651fdc4dd26172bcb71a85e6eb29eacd43;p=architektonas

diff --git a/src/geometry.cpp b/src/geometry.cpp
index 4cd229f..95d12c6 100644
--- a/src/geometry.cpp
+++ b/src/geometry.cpp
@@ -39,6 +39,29 @@ double Geometry::ParameterOfLineAndPoint(Point tail, Point head, Point point)
 }
 
 
+double Geometry::DistanceToLineFromPoint(Point tail, Point head, Point point)
+{
+	// Interpretation: given a line in the form x = a + tu, where u is the
+	// unit vector of the line, a is the tail and t is a parameter which
+	// describes the line, the distance of a point p to the line is given by:
+	// || (a - p) - ((a - p) . u) u ||
+	// We go an extra step: we set the sign to reflect which side of the line
+	// it's on (+ == to the left if head points away from you, - == to the
+	// right)
+	Vector line(tail, head);
+	Vector u = line.Unit();
+	Vector a_p = tail - point;
+	Vector dist = a_p - (u * (a_p).Dot(u));
+
+	double angle = Vector::Angle(tail, point) - line.Angle();
+
+	if (angle < 0)
+		angle += TAU;
+
+	return dist.Magnitude() * (angle < HALF_TAU ? +1.0 : -1.0);
+}
+
+
 Point Geometry::MirrorPointAroundLine(Point point, Point tail, Point head)
 {
 	// Get the vector of the intersection of the line and the normal on the