Added the function ZnPointCartesianToPolar that is the reciprocal of

ZnPointPolarToCartesian.

1 files changed, 21 insertions, 0 deletions

diff --git a/generic/Geo.c b/generic/Geo.c
index 1fde494..cb070e5 100644
--- a/generic/Geo.c
+++ b/generic/Geo.c
@@ -1276,6 +1276,27 @@ ZnPointInAngle(int      start_angle,
 }
 
 /*
+ * PointCartesianToPolar --
+ *	Convert a point in cartesian coordinates (delta_x, delta_y)
+ *  in polar coordinates (rho, theta)
+ *	in a reference system described by angle heading
+ *	(angles running clockwise) to a point .
+ *
+ */
+void
+ZnPointCartesianToPolar(ZnReal heading,
+                        ZnReal *rho,
+                        ZnReal *theta,  /* in degree -180 , + 180 */
+                        ZnReal delta_x,
+                        ZnReal delta_y)
+{
+  ZnReal theta_rad;
+  theta_rad = heading - ZnProjectionToAngle(delta_x,delta_y) - M_PI_2;
+  *theta = ZnRadDeg(theta_rad); 
+  *rho = sqrt( delta_x * delta_x + delta_y * delta_y );
+}
+
+/*
  * PointPolarToCartesian --
  *      Convert a point in polar coordinates (rho, theta)
  *      in a reference system described by angle heading