Changeset 34257 for trunk/psLib/src/math/psEllipse.c

Timestamp:

Jul 31, 2012, 3:55:33 PM (14 years ago)

Author:

eugene

Message:

update the comments to ellipse functions

File:

• trunk/psLib/src/math/psEllipse.c (modified) (2 diffs)

trunk/psLib/src/math/psEllipse.c

@@ -8 +8 @@
 #include "psTrace.h"
 #include "psEllipse.h"
+
+// we have four representations of the elliptical profile of a Gaussian
+// f = exp(-z) where z describes the elliptical contour at any flux level:
+
+// sigma shape: z = 0.5((x/sx)^2 + (y/sy)^2 + sxy*x*y)
+// sigma axes : z = 0.5((x/sa)^2 + (y/sb)^2), x,y rotated by theta 
+// moments    : z = 0.5(x^2/Mxx + y^2/Myy + x*y*Mxy)
+// polarization : e0, e1, e2
 
 // ellipse rotation (major, minor, theta) -> (x2, y2, xy)
@@ -107 +115 @@
 }
 
-// ellipse rotation (x2, y2, xy) -> (major, minor, theta)
+// ellipse rotation (x2, y2, xy) -> (major, minor, theta).  NOTE: major, minor are the
+// 1-sigma lengths in the major,minor directions assuming the moments represent a Gaussian
+// profile
 psEllipseAxes psEllipseMomentsToAxes(psEllipseMoments moments, double maxAR)
 {