diff -u -r1.8 -r1.9
--- HPSEcal.java	14 Apr 2011 22:15:46 -0000	1.8
+++ HPSEcal.java	22 Apr 2011 01:06:23 -0000	1.9
@@ -20,21 +20,27 @@

 /**
  * LCDD model for the HPS inner ECal.
  * 

- * The dimensions element defines x1, x2, y1, y2, and z as half the full dimension of a crystal.

+ * Coordinate System Notes:

  * 

- * The layout element defines the placement of the crystals.  The beamgap defines the
- * offset from the beamline in the Y coordinate, in the natural Geant4 coordinate system.
- * The nx attribute defines the number of crystals in the X coordinate.  The ny attribute
- * defines the number of crystals in Y, on each side of the beamline.  For example, to 
- * get 4 rows of crystals in Y, then ny would be 2.

+ * Beam travels in +X direction.
+ * Magnetic field is -Z (????).
+ * Y is the bend plane.

  * 

- * The position element has a z attribute that defines the distance from the origin
- * to the front face of the crystal array.

+ * The dimensions element defines the crystal HALF dimensions: x1, x2, y1, y2, and z.
+ * 
+ * The layout element defines the placement of the crystals.
+ * 
+ * <ul>
+ * <li>beamgap - offset from the beamline in the Y coordinate</li>
+ * <li>nx - number of crystals in X</li>
+ * <li>ny - number of crystals in Y along each side of beam</li>
+ * <li>dface - distance from origin to the face of the calorimeter along X</li>
+ * </ul>

  * 
  * @author Jeremy McCormick
  * @author Tim Nelson
  * 

- * @version $Id: HPSEcal.java,v 1.8 2011/04/14 22:15:46 jeremy Exp $

+ * @version $Id: HPSEcal.java,v 1.9 2011/04/22 01:06:23 jeremy Exp $

  */
 public class HPSEcal extends LCDDSubdetector
 {

@@ -51,42 +57,36 @@

     
     void addToLCDD(LCDD lcdd, SensitiveDetector sens) throws JDOMException
     {

-        // Get the half-dimensions of the calorimeter crystal.

+        if (sens == null)
+            throw new RuntimeException("SensitiveDetector is null!");
+        
+        // Crystal dimensions.

         Element dimensions = node.getChild("dimensions");
         double dx1 = dimensions.getAttribute("x1").getDoubleValue();
         double dx2 = dimensions.getAttribute("x2").getDoubleValue();
         double dy1 = dimensions.getAttribute("y1").getDoubleValue();
         double dy2 = dimensions.getAttribute("y2").getDoubleValue();
         double dz = dimensions.getAttribute("z").getDoubleValue();

-        
-        System.out.println("x1="+dx1);
-        System.out.println("x2="+dx2);
-        System.out.println("y1="+dy1);
-        System.out.println("y2="+dy2);
-        System.out.println("z="+dz);
-        

+                
+        // Crystal material.

         Element mat = node.getChild("material");
         String materialName = mat.getAttributeValue("name");
         

+        // Layout parameters.

         Element layout = node.getChild("layout");
         double beamgap = layout.getAttribute("beamgap").getDoubleValue();
         int nx = layout.getAttribute("nx").getIntValue();
         int ny = layout.getAttribute("ny").getIntValue();
         double dface = layout.getAttribute("dface").getDoubleValue();

-        
-        System.out.println("beamgap="+beamgap);
-        System.out.println("nx="+nx);
-        System.out.println("ny="+ny);
-        System.out.println("dface="+dface);
-        

+                
+        // Setup crystal logical volume.

         Trapezoid crystalTrap = new Trapezoid("crystal_trap", dx1, dx2, dy1, dy2, dz);
         Volume crystalLogVol = new Volume("crystal_volume", crystalTrap, lcdd.getMaterial(materialName));

+        crystalLogVol.setSensitiveDetector(sens);

         
         lcdd.add(crystalTrap);
         lcdd.add(crystalLogVol);

-        
-        Define define = lcdd.getDefine();
-        

+                      

         // Mother volume dimensions.
         double mx, my, mz;
         double margin = 1.1;

@@ -94,10 +94,9 @@

         my = ny*Math.max(dy2, dy1)*margin;
         mz = dz*margin;  
 

-        // Envelope box and logical volume for one section (upper and lower each use this for placement).
-        // TODO Turn off visualization of envelope vol.  Set daughters visible.

+        // Envelope box and logical volume for one section of ECal.

         Box momBox = new Box("mom_box", mx*2, my*2, mz*2);

-        Volume momVol = new Volume("mom_volume", momBox, lcdd.getMaterial("Air"));

+        Volume momVol = new Volume("mom_volume", momBox, lcdd.getMaterial("Air"));       

         
         lcdd.add(momBox);
         lcdd.add(momVol);

@@ -136,7 +135,8 @@

 
         double ycorrtot = 0;
         double zcorrtoty = 0;

-        //double fudgeFactor = .01;        

+        
+        Define define = lcdd.getDefine();

 
         for (int iy=1; iy<=ny; iy++)
         {

@@ -151,19 +151,20 @@

             
             for (int ix=0; ix<=nx; ix++)
             {                             

-                // Factor for even/odd.

+                // Coefficient for even/odd crystal

                 int coeffx = 2*ix;
                 if (!oddx)
                 {
                     coeffx -= 1;

+                    // For even number of crystals, the 0th is skipped.

                     if (ix==0)
                         continue;
                 }