Name: GRPOCL
Purpose: polygon clip
Category: GRAPHICS
File: pgplot.src
Author: T.J. Pearson
Use: see description below.
Description:
SUBROUTINE GRPOCL (N,PX,PY, EDGE, VAL, MAXOUT, NOUT, QX, QY)
INTEGER N, NOUT, EDGE, MAXOUT
REAL PX(*), PY(*), QX(*), QY(*)
REAL VAL
Clip a polygon against a rectangle: Sutherland-Hodgman algorithm.
this routine must be called four times to clip against each of the
edges of the rectangle in turn.
Arguments:
N (input, integer): the number of vertices of the polygon (at least
3).
PX, PY (input, real arrays, dimension at least N): world coordinates
of the N vertices of the input polygon.
EDGE (input, integer):
1: clip against left edge, X > XMIN=VAL
2: clip against right edge, X < XMAX=VAL
3: clip against bottom edge, Y > YMIN=VAL
4: clip against top edge, Y < YMIN=VAL
VAL (input, real): coordinate value of current edge.
MAXOUT (input, integer): maximum number of vertices allowed in
output polygon (dimension of QX, QY).
NOUT (output, integer): the number of vertices in the clipped polygon.
QX, QY (output, real arrays, dimension at least MAXOUT): world
coordinates of the NOUT vertices of the output polygon.
Updates: Oct 16, 1998: JPT automatically extracted from source.