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SUBROUTINE HIDIV (Z0, Z1,ZE,Z2, MX,MY, NX,NY, LX,LY, S,
X ROT, TILT, PL2)
C$ (Inclined View)
C$ Produce a parallel projection drawing of a single valued
C$ function defined in Cartesian coordinates, exhibiting arcs
C$ on the surface parallel to the coordinate axes. For
C$ greater variety in presentation, the entire figure may be
C$ rotated through an angle, which should be specified in
C$ degrees, and then tilted toward the observer. The scale of
C$ the drawing is adjusted to approximately fill the frame,
C$ and thus depends upon the rotation angle chosen. The
C$ arguments are:
C$
C$ Z0......Cutoff value. Only function values, ZE(I,J), above
C$ (S .GT. 0.0) or below (S .LT. 0) Z0 are visible.
C$ ZE......Array containing the surface. ZE(I,J) =
C$ F(X(I),Y(J)).
C$ Z1,Z2...Span of surface values.
C$ MX,MY...Actual declared dimensions of the array ZE(*,*).
C$ NX,NY...Sections of ZE(*,*) actually used.
C$ LX,LY...Increments in X and Y directions (.GT. 0). Values
C$ of LX and LY larger than 1 produce a coarser mesh
C$ on the drawing without losing the smoothness of the
C$ complete surface. LX should be an integral divisor
C$ of NX-1, and LY of NY-1. If this is not the case,
C$ the next smallest value which satisfies this
C$ requirement is used internally.
C$ S.......=+1.0, graph positive part of function,
C$ =-1.0, graph negative part of function,
C$ = 0.0, graph both positive and negative parts.
C$ If S = 0.0, the cutoff value Z0 has no effect.
C$ ROT.....Angle of rotation in degrees. Positive angles
C$ correspond to looking down the positive Z axis in a
C$ right-handed coordinate system and rotating
C$ counterclockwise. Rotation angles which are
C$ multiples of 90 degrees, or within a degree or so
C$ of such a number, should be avoided, since drawings
C$ then deteriorate because of the way the scan
C$ algorithm in the hidden line routine works.
C$ TILT....Angle of tilt in degrees. Tilt is positive
C$ counterclockwise looking down the horizontal axis
C$ to the origin. Thus TILT=0.0 corresponds to an
C$ overhead view looking down the positive Z axis
C$ toward the origin, and gives a totally
C$ uninteresting display of the X-Y grid. Negative
C$ TILT angles tip the top part of the rotated surface
C$ away from the observer around the horizontal axis.
C$ TILT=-90.0 corresponds to an edge-on view of the
C$ surface. Recommended values are in the range
C$ -20..-70.
C$ PL2.....2-D pen movement subroutine, usually PL2CA
C$
C$ (04-FEB-82)