Previous: pl2tp Up: ../plot79_p.html Next: pl3ca
SUBROUTINE PL2TR (U,V,VISBLE)
C$ (2-D Triangular Pen Movement)
C$ Change the variables (U,V) to the Cartesian coordinates
C$ (X,Y) so as to define points directly in triangular
C$ coordinates and graph their projection on the X-Y plane,
C$ where the Y axis is vertical and the X axis is positive to
C$ the right. (U,V) are both assumed to be scaled to the unit
C$ interval. The Cartesian coordinates (X,Y) are adjusted to
C$ the unit interval and passed to MOVA2/LINA2.
C$
C$ Triangular coordinates (U,V,W) are defined as the
C$ perpendicular distances of a point from each of the three
C$ edges of an equilateral triangle. These are not
C$ independent, since such a triangle has the property that
C$ U+V+W is equal to the height. Taking a triangle of unit
C$ height gives U+V+W=1, which is the standard convention
C$ adopted for triangular coordinates. The edges are chosen
C$ so that U is measured from the left edge, and V from the
C$ bottom edge. These are easily remembered, since (U,V) is
C$ then almost like (X,Y), and V is vertical. The triangle is
C$ sketched as follows:
C$
C$
C$ **
C$ E * * E
C$ D * * D
C$ G * * G
C$ E * * E
C$ - * * -
C$ U * * W
C$ ****************
C$ EDGE-V
C$
C$ (09-APR-82)