best_rays

best_rays(rays)
returns 5element (x,y,z,theta,phi) representation of RAYS.
The first dimension of RAYS may be length 3, 5, or 6 to represent
the ray(s) in TDG/DIRT coordinates (x,y,theta), "best" coordinates
(x,y,z,theta,phi), or internal coordinates (cos,sin,y,z,x,r),
respectively. The first dimension of the result always has length 5.
The "best" coordinate system is the easiest to visualize:
(x,y,z) represents any point on the ray, while (theta,phi)
represents the ray direction in standard spherical coordinates
relative to the +zaxis. Namely, theta is the angle from the
+zdirection to the ray direction (between 0 and pi), and phi is
the counterclockwise angle from the +xaxis to the projection of
the ray direction into the xyplane, assuming xyz is a righthanded
coordinate system.
As a specification of a ray, this system is doubly redundant because
the point (x,y,z) could be any point on the ray, and the underlying
mesh through which the ray propagates is cylindrically symmetric about
the zaxis.
However, the slimits parameter  used to specify the points along
a ray where the transport integration starts and stops  is
measured from the point (x,y,z) specified as a part of the
(x,y,z,theta,phi) ray coordinate. Thus, any change in the point
(x,y,z) on a ray must be accompanied by a corresponding change in
the slimits for that ray.
interpreted function, defined at i/rays.i line 40
