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MGHGRCOLORPLANE__DEFINE

MGHGRCOLORPLANE__DEFINE

Class Name


  MGHgrColorPlane

Purpose



  The MGHgrColorPlane implements a flat, coloured surface consisting
  of a rectangular array of quadrilateral cells, optionally with
  some of the cells omitted. Colours are either uniform over the
  cells (STYLE=0) or interpolated from the vertices (STYLE=1). A
  "colour plane" is a lot like an image, but has more flexibility in
  the pixel geometry & shading.
  The MGHgrColorPlane is used as a base for the density plot class,
  MGHgrDensityPlane.
  I have two different colour plane implementations: the
  MGHgrColorPolygon displays data using an IDLgrPolygon and the
  MGHgrColorSurface displays data using an IDLgrsurface. These two
  implementations are largely interchangeable but have various
  strengths and weaknesses. In the past I have dithered about which
  one should be labelled "MGHgrColorPlane". Now the MGHgrColorPlane
  is just a trivial subclass of one of them. Last time I looked it
  was MGHgrColorSurface-see MGHgrColorPlane__Define below.
  I haven't yet sorted out the full story about performance of the
  two colour-plane implementations. For interpolated colour (STYLE=1)
  they are about the same but for block colour (STYLE=0) the
  IDLgrSurface-based implementation takes somewhat longer to draw
  to a window and (I think) *much* longer to draw to a Postscript file.
  I think this is because it is based on a lego-style surface.
  In versions 5.4
  and before, the IDLgrSurface-based implementation looked very odd
  when the horizontal grid was rotated with STYLE = 0. This was
  fixed in version 5.5.
  Both the MGHgrColorPolygon and the MGHgrColorSurface inherits from
  IDLgrModel, to which the surface or polygon is added. This avoids
  the need to carry a 2-D array of Z information around with the
  object.
  For further information see the documentation for the
  MGHgrColorPolygon and MGHgrColorSurface classes.
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  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.
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Modification History


  Mark Hadfield, 2000-12:
    The name MGHgrColorPlane has been used for various classes in
    the past. Now it is a trivial subclass of the polygon-based
    colour plane, MGHgrColorPolygon.
  Mark Hadfield, 2001-07:
    Now a subclass of the surface-based colour plane,
    MGHgrColorSurface.



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