anchor.diff:    s_rot  = s
     xp_rot = xp
   
  -  s_shift  =  s_rot*c_cnTilt+x_rot*c_snTilt
  -  x_shift  = -s_rot*c_snTilt+x_rot*c_cnTilt
  +  s_shift  =  s_rot*c_cnTilt + x_rot*c_snTilt
  +  x_shift  = -s_rot*c_snTilt + x_rot*c_cnTilt
     xp_shift = xp_rot + cry_tilt
   
     ! 2nd: shift back the reference frame
  
positive.code:   end if
  
    ! 3rd: shift to new S=Length position
    x = xp*(c_length-s) + x
    z = zp*(c_length-s) + z
    s = c_length
  
    nabs = 0
  
negative.code:   c_orient = cdb_cryOrient(icoll)
    c_miscut = cdb_cryMiscut(icoll)
    cry_bend = cry_length/c_rcurv
    c_cBend  = cos_mb(cry_bend)
    c_sBend  = sin_mb(cry_bend)
    c_cpTilt = cos_mb(cry_tilt)
    c_spTilt = sin_mb(cry_tilt)
    c_cnTilt = cos_mb(-cry_tilt)
  