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MGH_POLYCLIP

MGH_POLYCLIP

Name


  MGH_POLYCLIP

Purpose


  Clip an arbitrary polygon on the X-Y plane to a line parallel
  to the X or Y axis using the Sutherland-Hodgman algorithm.

Category


  Graphics, Region of Interest, Geometry

Calling Sequence


  result = MGH_POLYCLIP(clip, dir, neg, polin, COUNT=count)

Return Value


  The function returns the clipped polygon as a [2,n] array. The
  second dimension will equal the value of the COUNT argument, except
  where COUNT is 0 in which case the return value is -1.

Positional Parameters


  cval (input, numeric sclar)
    The value of X or Y at which clipping is to occur
  dir (input, integer scalar)
    Specifies whether clipping value is an X (dir = 0) or Y (dir =
    1) value.
  neg (input, integer scalar)
    Set this argument to 1 to clip to the negtive side, 0 to clip to
    the positive side.
  polin (input, floating array)
    A [2,m] vector defining the polygon to be clipped.

Keyword Parameters


  COUNT (output, integer)
    The number of vertices in the clipped polygon.

Procedure


  The polygon is clipped using the Sutherland-Hodgman algorithm.
  This function is based on JD Smith's implementation of the
  Sutherland-Hodgman algorithm in his POLYCLIP function. He can
  take all of the credit and none of the blame.
###########################################################################
  This software is provided subject to the following conditions:
  1. NIWA makes no representations or warranties regarding the
    accuracy of the software, the use to which the software may
    be put or the results to be obtained from the use of the
    software. Accordingly NIWA accepts no liability for any loss
    or damage (whether direct of indirect) incurred by any person
    through the use of or reliance on the software.
  2. NIWA is to be acknowledged as the original author of the
    software where the software is used or presented in any form.
###########################################################################

Modification History


  Mark Hadfield, 2001-10:
    Written, based on JD Smith's POLYClIP.



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