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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.
###########################################################################
  Copyright (c) 2000-2014 NIWA:
  http://www.niwa.co.nz/
  Licensed under the MIT open source license:
  http://www.opensource.org/licenses/mit-license.php
###########################################################################

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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