diff -u -r1.1 -r1.2
--- TrackToTrackPOCAInCalorimeter.java	29 Sep 2005 21:04:50 -0000	1.1
+++ TrackToTrackPOCAInCalorimeter.java	14 Oct 2005 17:43:30 -0000	1.2
@@ -1,6 +1,13 @@

 package structural.likelihood; // package org.lcsim.recon.cluster.structural.likelihood;
 

+import hep.physics.vec.BasicHep3Vector;
+import hep.physics.vec.Hep3Vector;
+import hep.physics.vec.VecOp;
+

 import org.lcsim.event.Cluster;

+import org.lcsim.recon.cluster.util.TensorClusterPropertyCalculator;
+import org.lcsim.recon.cluster.util.BasicCluster;
+import org.lcsim.util.swim.Line;

 
 public class TrackToTrackPOCAInCalorimeter implements StructuralLikelihoodQuantity
 {

@@ -10,6 +17,34 @@

 
     public double evaluate(Cluster track1, Cluster track2) 
     {

+        if (track1.getCalorimeterHits().size()<4 || track2.getCalorimeterHits().size()<4) {
+            throw new QuantityNotDefinedException("Need 4+ hits in each cluster to get direction, but they have "
+                                                  +track1.getCalorimeterHits().size()
+                                                  +" and "
+                                                  +track2.getCalorimeterHits().size()
+                                                  +" respectively.");
+        }
+
+        // Need to find directions of the two clusters.
+        Line line1 = MiscUtilities.makeLine(track1);
+        Line line2 = MiscUtilities.makeLine(track2);
+
+        // Find the POCA:
+	double[] distancesAlongLinesToPOCAs = Line.getPOCAOfLines(line1, line2);
+	Hep3Vector nearestPointOnLine1 = line1.getPointAtDistance(distancesAlongLinesToPOCAs[0]);
+	Hep3Vector nearestPointOnLine2 = line2.getPointAtDistance(distancesAlongLinesToPOCAs[1]);
+	// Find the mean of these two points -- that's the POCA
+	Hep3Vector poca = VecOp.mult(0.5, VecOp.add(nearestPointOnLine1, nearestPointOnLine2));
+
+        boolean pocaInCalorimeter = isPointInCalorimeter(poca);
+        if (pocaInCalorimeter) {
+            return 1.0;
+        } else {
+            return 0.0;
+        }
+    }
+ 
+    protected boolean isPointInCalorimeter(Hep3Vector point) {

 	throw new AssertionError("Not implemented");
     }
 }