Intersection between two circles (3)
Given O1(x1,y1,z1), O2(x2,y2,z2), the center of the circles and r1 and r2, 
  their Radius
Given M(x,y,z) the intersection, then another way is ...
 O1H = x
 
  O1H = x 
MH = h
0102 = d
H02 = d - x
(1) R12 
  = h2 + x2
(2) R22 
  = h2 + (d - x )2 
  = h2 + d2 -2dx + 
  x2
(2) - (1) R22 
  - R12 = d2 
  - 2dx
 
=> x = (d2 
  - R22 + R12)/2d
(1) h = +/- squareroot(R12 
  - x2)
M = O1 + O1 
  H +/- HM
Then O1H = x. O1O2/||O1O2||      
  then inverse -x and y of  O1O2/||O1O2|| vector to get an orthogonal vector