functions in rays.i - b

             best_rays(rays)  
 
     returns 5-element (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 +z-axis.  Namely, theta is the angle from the  
     +z-direction to the ray direction (between 0 and pi), and phi is  
     the counterclockwise angle from the +x-axis to the projection of  
     the ray direction into the xy-plane, assuming xyz is a right-handed  
     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 z-axis.  
     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