SUBROUTINE PLT3DH

   PLT3DH is a routine which operates in a similar as PLOT but in 3-d. It is, however, independent of PLOT3D. A relative  origin is maintained (separate from the PLOT routine parameters) which is initalized by INIT3DH. PLT3DH calls PLOT after transforming (x,y,z). PLT3DH is also independent of the  SKETCH routine. Lines plotted with PLT3DH are always completely visible. To use the hidden line removal SKETCH must be used.

CALL PLT3DH (x,y,z,i)

x,y,z (R): coordinates of point (in 3 space)
i     (I): plot function parameter
           =  0: line color control
                  x is the line color
                  if x < 0 screen is cleared
                  if x >= 0 plotting angle (in PLOT) becomes y
           =  2: draw to (x,y,z) with 'pen down'
           = -2: same as i=2. Point (x,y,z) becomes new origin
           =  3: move to (x,y,z) with 'pen up'
           = -3: same as i=3. Point (x,y,z) becomes new origin
           =  9: erase to (x,y,z) (erase on Ramtek is color 0)
           = -9: erase to (x,y,z) becomes new origin