lcsim/src/org/lcsim/recon/tracking/spacegeom
diff -u -r1.1 -r1.2
--- TwoSegment.java 25 Jul 2007 16:59:29 -0000 1.1
+++ TwoSegment.java 7 May 2008 21:39:02 -0000 1.2
@@ -1,137 +1,154 @@
-package org.lcsim.recon.tracking.spacegeom;
-/**
- * A line segment in two dimensions.
- *
- *
- *@author Norman A. Graf
- *@version 1.0
- *
- */
-
-public class TwoSegment
-{
- private TwoSpacePoint _a;
- private TwoSpacePoint _b;
- private double _length;
-
- /**
- * Constructor
- *
- * @param a beginning TwoSpacePoint
- * @param b ending TwoSpacePoint
- */
- public TwoSegment(TwoSpacePoint a, TwoSpacePoint b)
- {
- _a = a;
- _b = b;
- _length = TwoSpacePoint.distance(_a,_b);
- }
-
-
- /**
- * Fetch the starting point
- *
- * @return beginning TwoSpacePoint
- */
- public TwoSpacePoint startPoint()
- {
- return _a;
- }
-
-
- /**
- * Fetch the ending point
- *
- * @return ending TwoSpacePoint
- */
- public TwoSpacePoint endPoint()
- {
- return _b;
- }
-
-
- /**
- * Return the length of the segment
- *
- * @return length of the segment
- */
- public double length()
- {
- return _length;
- }
-
-
- /**
- * calculate the minimum distance between this segment and a point p
- *
- * @param p The TwoSpacePoint
- * @return the distance between the point and this segment
- */
- public double minimumDistance(TwoSpacePoint p)
- {
- double u = ( ( ( p.x() - _a.x() ) * ( _b.x() - _a.x() ) ) +
- ( ( p.y() - _a.y() ) * ( _b.y() - _a.y() ) ) )/(_length*_length);
- double xint = ( _a.x() + u * (_b.x() - _a.x()) ) - p.x();
- double yint = ( _a.y() + u * (_b.y() - _a.y()) ) - p.y();
- double dist = Math.sqrt( xint*xint + yint*yint );
- return dist;
- }
-
-
-
- /**
- * return intersection point of two line segments
- *
- * @param a The first line segment
- * @param b The second line segment
- * @return The intersection point of the two segments.
- * null if lines are parallel or intersect outside of segment boundaries.
- */
- public static TwoSpacePoint intersection(TwoSegment a, TwoSegment b)
- {
- // set some things up
- double x1 = a.startPoint().x();
- double y1 = a.startPoint().y();
- double x2 = a.endPoint().x();
- double y2 = a.endPoint().y();
- double x3 = b.startPoint().x();
- double y3 = b.startPoint().y();
- double x4 = b.endPoint().x();
- double y4 = b.endPoint().y();
-
- double denom = (y4-y3)*(x2-x1)-(x4-x3)*(y2-y1);
-
- if(denom==0) return null;// lines are parallel
-
- double numa = (x4-x3)*(y1-y3)-(y4-y3)*(x1-x3);
-
- if(numa==0) return null; // lines are coincident, no unique intersection
-
- double ua = numa/denom;
-
- if(ua<0 || ua >1.) return null; // intersect outside of segment a
-
- double numb = (x2-x1)*(y1-y3)-(y2-y1)*(x1-x3);
- double ub = numb/denom;
- if(ub<0 || ub >1.) return null; // intersect outside of segment b
-
- // should now have a valid intersection point...
- double xend = x3+ub*(x4-x3);
- double yend = y3+ub*(y4-y3);
-
- return new CartesianTwoPoint(xend, yend);
-
- }
-
-
- /** String representation of this object
- *
- *
- * @return String representation of this object
- */
- public String toString()
- {
- return "TwoSegment from "+_a+" \n to "+_b +" \n length: "+_length;
- }
-
-}
+package org.lcsim.recon.tracking.spacegeom;
+import static java.lang.Math.atan2;
+import static java.lang.Math.PI;
+/**
+ * A line segment in two dimensions.
+ *
+ *
+ *@author Norman A. Graf
+ *@version 1.0
+ *
+ */
+
+public class TwoSegment
+{
+ private TwoSpacePoint _a;
+ private TwoSpacePoint _b;
+ private double _length;
+
+ /**
+ * Constructor
+ *
+ * @param a beginning TwoSpacePoint
+ * @param b ending TwoSpacePoint
+ */
+ public TwoSegment(TwoSpacePoint a, TwoSpacePoint b)
+ {
+ _a = a;
+ _b = b;
+ _length = TwoSpacePoint.distance(_a,_b);
+ }
+
+
+ /**
+ * Fetch the starting point
+ *
+ * @return beginning TwoSpacePoint
+ */
+ public TwoSpacePoint startPoint()
+ {
+ return _a;
+ }
+
+
+ /**
+ * Fetch the ending point
+ *
+ * @return ending TwoSpacePoint
+ */
+ public TwoSpacePoint endPoint()
+ {
+ return _b;
+ }
+
+
+ /**
+ * Return the length of the segment
+ *
+ * @return length of the segment
+ */
+ public double length()
+ {
+ return _length;
+ }
+
+ /**
+ * Return the azimuthal angle of this segment, the angle from point 1 to 2
+ * zero & 3pi/4 is vertical
+ * pi and 2pi is horizontal
+ * @return the angle from point 1 to point 2
+ */
+ public double phi()
+ {
+ double x = _a.x() - _b.x();
+ double y = _a.y() - _b.y();
+ double phi = atan2(y,x);
+ if(phi<0) phi+= 2.*PI;
+ return phi;
+ }
+
+
+ /**
+ * calculate the minimum distance between this segment and a point p
+ *
+ * @param p The TwoSpacePoint
+ * @return the distance between the point and this segment
+ */
+ public double minimumDistance(TwoSpacePoint p)
+ {
+ double u = ( ( ( p.x() - _a.x() ) * ( _b.x() - _a.x() ) ) +
+ ( ( p.y() - _a.y() ) * ( _b.y() - _a.y() ) ) )/(_length*_length);
+ double xint = ( _a.x() + u * (_b.x() - _a.x()) ) - p.x();
+ double yint = ( _a.y() + u * (_b.y() - _a.y()) ) - p.y();
+ double dist = Math.sqrt( xint*xint + yint*yint );
+ return dist;
+ }
+
+
+
+ /**
+ * return intersection point of two line segments
+ *
+ * @param a The first line segment
+ * @param b The second line segment
+ * @return The intersection point of the two segments.
+ * null if lines are parallel or intersect outside of segment boundaries.
+ */
+ public static TwoSpacePoint intersection(TwoSegment a, TwoSegment b)
+ {
+ // set some things up
+ double x1 = a.startPoint().x();
+ double y1 = a.startPoint().y();
+ double x2 = a.endPoint().x();
+ double y2 = a.endPoint().y();
+ double x3 = b.startPoint().x();
+ double y3 = b.startPoint().y();
+ double x4 = b.endPoint().x();
+ double y4 = b.endPoint().y();
+
+ double denom = (y4-y3)*(x2-x1)-(x4-x3)*(y2-y1);
+
+ if(denom==0) return null;// lines are parallel
+
+ double numa = (x4-x3)*(y1-y3)-(y4-y3)*(x1-x3);
+
+ if(numa==0) return null; // lines are coincident, no unique intersection
+
+ double ua = numa/denom;
+
+ if(ua<0 || ua >1.) return null; // intersect outside of segment a
+
+ double numb = (x2-x1)*(y1-y3)-(y2-y1)*(x1-x3);
+ double ub = numb/denom;
+ if(ub<0 || ub >1.) return null; // intersect outside of segment b
+
+ // should now have a valid intersection point...
+ double xend = x3+ub*(x4-x3);
+ double yend = y3+ub*(y4-y3);
+
+ return new CartesianTwoPoint(xend, yend);
+
+ }
+
+
+ /** String representation of this object
+ *
+ *
+ * @return String representation of this object
+ */
+ public String toString()
+ {
+ return "TwoSegment from "+_a+" \n to "+_b +" \n length: "+_length;
+ }
+
+}
