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SUBROUTINE PL3CY (T,Z,R,VISBLE)
C$ (3-D Cylindrical Pen Movement)
C$ Change the angular variables (T,Z,R) to the Cartesian
C$ coordinates X,Y,Z so as to define directly in cylindrical
C$ polar coordinates points which lie upon the surface of a
C$ cylinder and graph their projection on the X-Z plane, where
C$ the Z axis is vertical and the X axis is positive to the
C$ right. Points with positive Y values lie behind the plane
C$ and are marked as invisible. (T,Z,R) are all assumed to be
C$ scaled to the unit interval. The Cartesian coordinates
C$ (X,Y,Z) are adjusted to the unit interval and passed to
C$ MOVA3/LINA3 as (X,Z,Y), so that the default view plane (the
C$ X-Y plane) will receive the image. The cylindrical
C$ coordinate ranges are
C$
C$ 0 .LE. PHI .LE. 2*pi
C$ -infinity .LE. ZETA .LE. +infinity
C$ 0 .LE. RHO .LE. +infinity
C$
C$ See H. Margenau and G.M. Murphy, "Mathematics of Physics
C$ and Chemistry", 2nd Ed., Van Nostrand (1956), Vol 1, p.
C$ 178. These are related to the Cartesian coordinates by
C$
C$ X = RHO*COS(PHI)
C$ Y = RHO*SIN(PHI)
C$ Z = ZETA
C$
C$ The coordinate surfaces are
C$ (1) Right circular cylinders coaxial with the Z axis (RHO =
C$ constant)
C$ (2) Half planes containing the Z axis (PHI = constant)
C$ (3) Planes parallel to the X-Y plane (ZETA = constant).
C$
C$ To obtain coordinates (T,Z,R) expressed on the unit
C$ interval, (PHI,ZETA,RHO) are transformed as follows:
C$
C$ T = PHI/TWOPI
C$ Z = ZETA (simply clipped to 0..1)
C$ R = RHO (simply clipped to 0..1)
C$ (09-APR-82)