.PS
include(liborth.m4)
cct_init

# Usual defs...
qrt=dimen_/4;
hlf=dimen_/2;
dim=dimen_;

Org: Here

orthogaxes(5*dim)

# Need to put the colour down first, then overwrite the black theta phi
# lines. Note that the dotted line gets obliterated correctly. Order :-)
orthogmove(4*dim, pi_/4-pi_/40, pi_/3-pi_/30); 
A:line to Org
orthogmove(4*dim, pi_/4-pi_/40, pi_/3+pi_/30); 
B:line dotted to Org
orthogmove(4*dim, pi_/4+pi_/40, pi_/3-pi_/30); 
C:line to Org
orthogmove(4*dim, pi_/4+pi_/40, pi_/3+pi_/30); 
D:line to Org

# line must be a closed path. This is seriously sexy.
line invis shaded "green" from A.start to B.start \
  then to D.start then to C.start then to A.start;\
  move to Org

orthogphicirc(4*dim, pi_/2, 0, pi_/2)

orthogthetacirc(4*dim, 0, 0, pi_/2)
orthogthetacirc(4*dim, pi_/2, 0, pi_/2)

orthogphicirc(4*dim, pi_/4-pi_/40, 0, pi_/2)
orthogphicirc(4*dim, pi_/4+pi_/40, 0, pi_/2)

orthogthetacirc(4*dim, pi_/3-pi_/30, 0, pi_/2)
orthogthetacirc(4*dim, pi_/3+pi_/30, 0, pi_/2)

orthogmove(4*dim, pi_/2, pi_/3-pi_/30); line to Org; 
orthogmove(4*dim, pi_/2, pi_/3+pi_/30); line to Org;

orthogphicirc(2*dim, pi_/2, 0, pi_/3-pi_/30)
# Cunning use of the (tiny) last line fragment drawn...
arrow from last line.start to last line.end
orthogmove(2.5*dim, pi_/2, pi_/3/2); "$\phi$"

move to Org
orthogphicirc(2.6*dim, pi_/2, pi_/3-pi_/30, pi_/3 + pi_/30)
arrow from last line.start to last line.end
orthogmove(3*dim, pi_/2, pi_/3); "$d\phi$"

orthogmove(4*dim, pi_/2, pi_/3);
spline <- down_ dim/3 right_ dim/3 then right_ dim/2
" $r\ d\phi$" ljust_

orthogmove(4*dim, pi_/4-pi_/40, pi_/3+pi_/30)
line to Org + (0, 4*dim*cos(pi_/4-pi_/40))
orthogmove(4*dim, pi_/4-pi_/40, pi_/3-pi_/30)
line to Org + (0, 4*dim*cos(pi_/4-pi_/40))
spline <- from last line.center down_ dim/3 left_ dim/3 \
  then left_ 2*dim
right_  
"$r \sin\theta$  " rjust_

move to Org
orthogthetacirc(1.2*dim, pi_/3-pi_/30, 0, pi_/4-pi_/40)
arrow from last line.start to last line.end
orthogmove(1.5* dim, (pi_/4-pi_/40)/2, pi_/3-pi_/30); "$\theta$"

move to Org
orthogthetacirc(2*dim, pi_/3-pi_/30, pi_/4-pi_/40, pi_/4+pi_/40)
arrow from last line.start to last line.end
orthogmove(2.5*dim, pi_/4, pi_/3-pi_/30); "$d\theta$"

orthogmove(4*dim, pi_/4, pi_/3+pi_/30);
spline <- up_ dim/3 right_ dim/3 then right_ 0.75*dim;
" $r\ d\theta$" ljust_

orthogmove(4*dim, pi_/4-pi_/40, pi_/3)
spline <- up_ dim/3 left_ dim/3 then up_ dim/3 right_ \
  dim/3 then up_ dim/3 right_ dim
" $r\sin\theta\  d\phi$"  ljust_

orthogmove(4*dim, pi_/4, pi_/3); dot
spline <- down_ dim/3 right_ dim/3 then down_ dim/5 \
  right_ 1.5*dim
" $dA = r^2 \sin\theta\ d\theta\ d\phi$" ljust_

"\tiny StdCoord" at (2*dim,-2*dim)
.PE