lcsim/src/org/lcsim/util/swim
diff -u -r1.15 -r1.16
--- Helix.java 26 Oct 2005 00:36:23 -0000 1.15
+++ Helix.java 28 Oct 2005 07:57:27 -0000 1.16
@@ -20,7 +20,7 @@
* All quantities in this class are dimensionless. It has no dependencies
* except for Hep3Vector (which could easily be removed).
* @author tonyj
- * @version $Id: Helix.java,v 1.15 2005/10/26 00:36:23 jstrube Exp $
+ * @version $Id: Helix.java,v 1.16 2005/10/28 07:57:27 jstrube Exp $
*/
public class Helix implements Trajectory
{
@@ -31,14 +31,14 @@
* @param origin A point on the helix
* @param radius The <em>signed</em> radius of curvature of the helix.
* The conventions is such that for <em>positive</em> radii,
- * the direction is <em>counter-clockwise</em>.
+ * the direction is <em>clockwise</em>.
* @param phi The azimuthal angle of the helix <em>momentum</em> in x-y plane w/rt positive x-axis at the origin
* @param lambda The dip angle w/rt positive part of the x-y plane
*/
public Helix(Hep3Vector origin, double radius, double phi, double lambda)
{
- if (abs(lambda) > PI/2.)
- throw new IllegalArgumentException("lambda = " + lambda + " is outside of -PI/2<lambda<PI/2");
+// if (abs(lambda) > PI/2.)
+// throw new IllegalArgumentException("lambda = " + lambda + " is outside of -PI/2<lambda<PI/2");
this.origin = origin;
this.radius = radius;
this.phi = phi;
@@ -56,17 +56,18 @@
/**
* returns a point on the Helix at a distance alpha from the origin along
- * the trajectory. alpha == 2*PI*radius is one rotation in the x-y plane
+ * the trajectory. alpha == 2*PI*radius/cos(lambda) is one rotation in the x-y plane
*/
public Hep3Vector getPointAtDistance(double alpha)
{
- double darg = alpha*cosLambda/abs(radius) - phi;
+ double darg = alpha*cosLambda/radius - phi;
double x = xCenter + radius*sin( darg );
double y = yCenter + radius*cos( darg );
double z = origin.z() + alpha*sinLambda;
return new BasicHep3Vector(x,y,z);
}
+
public double getDistanceToZPlane(double z)
{
return (z - origin.z())/sinLambda;
@@ -110,7 +111,7 @@
// first, the point needs to be translated into the first period
Hep3Vector xDiff = VecOp.sub(origin, point);
- double zPos = xDiff.z();
+ double zPos = abs(xDiff.z());
int addedQuarterPeriods = 0;
// these are two mutually exclusive cases and two while loops
// may not be the best way to express this
@@ -186,8 +187,8 @@
}
private Hep3Vector origin;
- private double xCenter;
- private double yCenter;
+ double xCenter;
+ double yCenter;
private double radius;
private double sinLambda;
private double cosLambda;
lcsim/test/org/lcsim/util/swim
diff -u -r1.9 -r1.10
--- HelixTest.java 26 Oct 2005 00:36:24 -0000 1.9
+++ HelixTest.java 28 Oct 2005 07:57:27 -0000 1.10
@@ -12,7 +12,7 @@
/**
*
* @author tonyj
- * @version $Id: HelixTest.java,v 1.9 2005/10/26 00:36:24 jstrube Exp $
+ * @version $Id: HelixTest.java,v 1.10 2005/10/28 07:57:27 jstrube Exp $
*/
public class HelixTest extends TestCase
{
@@ -84,26 +84,26 @@
assertEquals(0,helix.getDistanceToInfiniteCylinder(0),1e-14);
}
-// public void testHelix2()
-// {
-// Hep3Vector origin = new BasicHep3Vector(0,0,0);
-// double radius = -1;
-// double phi = Math.PI/2;
-// double lambda = -Math.PI/4;
-// Helix helix = new Helix(origin,radius,phi,lambda);
-//
-// assertEquals(origin, helix.getPointAtDistance(0));
-// double d = Math.PI*2*Math.sqrt(2);
-// assertEquals(new BasicHep3Vector(0,0,-Math.PI*2), helix.getPointAtDistance(d));
-// assertEquals(new BasicHep3Vector(-2,0,-Math.PI), helix.getPointAtDistance(d/2));
-//
-// assertEquals(d/2,helix.getDistanceToZPlane(-Math.PI));
-// assertEquals(d,helix.getDistanceToZPlane(-Math.PI*2));
-// assertTrue(Double.isNaN(helix.getDistanceToInfiniteCylinder(3)));
-// assertEquals(d/2,helix.getDistanceToInfiniteCylinder(2),1e-14);
-// assertEquals(1.4809609793861218,helix.getDistanceToInfiniteCylinder(1),1e-14);
-// assertEquals(0,helix.getDistanceToInfiniteCylinder(0),1e-14);
-// }
+ public void testHelix2()
+ {
+ Hep3Vector origin = new BasicHep3Vector(0,0,0);
+ double radius = -1;
+ double phi = Math.PI/2;
+ double lambda = -Math.PI/4;
+ Helix helix = new Helix(origin,radius,phi,lambda);
+
+ assertEquals(origin, helix.getPointAtDistance(0));
+ double d = Math.PI*2*Math.sqrt(2);
+ assertEquals(new BasicHep3Vector(0,0,-Math.PI*2), helix.getPointAtDistance(d));
+ assertEquals(new BasicHep3Vector(-2,0,-Math.PI), helix.getPointAtDistance(d/2));
+
+ assertEquals(d/2,helix.getDistanceToZPlane(-Math.PI));
+ assertEquals(d,helix.getDistanceToZPlane(-Math.PI*2));
+ assertTrue(Double.isNaN(helix.getDistanceToInfiniteCylinder(3)));
+ assertEquals(d/2,helix.getDistanceToInfiniteCylinder(2),1e-14);
+ assertEquals(1.4809609793861218,helix.getDistanceToInfiniteCylinder(1),1e-14);
+ assertEquals(0,helix.getDistanceToInfiniteCylinder(0),1e-14);
+ }
public void testHelix3() throws IOException
{
@@ -283,16 +283,49 @@
Helix helix1 = new Helix(origin, radius, phi, lambda);
Helix helix2 = new Helix(origin, -radius, phi, lambda);
- // momentum conservation
for (int i=0; i<25; ++i) {
Hep3Vector tangentAtThisPiece_1 = helix1.getTangentAtDistance(i*.37);
Hep3Vector tangentAtThisPiece_2 = helix2.getTangentAtDistance(i*.37);
+ // momentum conservation
assertEquals(tangentAtThisPiece_1.magnitude(), helix1.getTangentAtDistance((i+1)*.37).magnitude());
assertEquals(tangentAtThisPiece_2.magnitude(), helix2.getTangentAtDistance(i*.37).magnitude());
+ // both positively and negatively charged tracks must be moving forward
assertEquals(tangentAtThisPiece_1.z(), tangentAtThisPiece_2.z());
}
}
+ public void testCurvature() {
+ Hep3Vector origin = new BasicHep3Vector(3, 6, 9);
+ double radius = 1.5;
+ double phi = Math.PI/2;
+ double lambda = 0;
+ for (int iPhi=0; iPhi<50; ++iPhi) {
+ Helix helix1 = new Helix(origin, radius, iPhi*phi, lambda);
+ Helix helix2 = new Helix(origin, -radius, iPhi*phi, lambda);
+ Helix helix5 = new Helix(origin, radius, Math.PI-iPhi*phi, lambda);
+ Helix helix6 = new Helix(origin, -radius, Math.PI-iPhi*phi, lambda);
+ assertEquals(helix1.yCenter, helix6.yCenter, 1e-10);
+ assertEquals(helix1.xCenter, helix5.xCenter, 1e-10);
+ assertEquals(helix2.xCenter, helix6.xCenter, 1e-10);
+ assertEquals(helix2.yCenter, helix5.yCenter, 1e-10);
+ }
+ Helix helix1 = new Helix(origin, radius, phi, lambda);
+ Helix helix2 = new Helix(origin, -radius, phi, lambda);
+
+ Hep3Vector h1 = helix1.getPointAtDistance(Math.PI/2*radius);
+ assertEquals(h1.x(), 4.5, 1e-14);
+ assertEquals(h1.y(), 7.5, 1e-14);
+ Hep3Vector h2 = helix2.getPointAtDistance(Math.PI/2*radius);
+ assertEquals(h2.x(), 1.5, 1e-14);
+ assertEquals(h2.y(), 7.5, 1e-14);
+ Hep3Vector h3 = helix1.getPointAtDistance(-Math.PI/2*radius);
+ assertEquals(h3.x(), 4.5, 1e-14);
+ assertEquals(h3.y(), 4.5, 1e-14);
+ Hep3Vector h4 = helix2.getPointAtDistance(-Math.PI/2*radius);
+ assertEquals(h4.x(), 1.5, 1e-14);
+ assertEquals(h4.y(), 4.5, 1e-14);
+ }
+
private void assertEquals(Hep3Vector v1, Hep3Vector v2)
{
