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MGHGRDENSITYRECT__DEFINE

MGHGRDENSITYRECT__DEFINE

Class Name


  MGHgrDensityRect

Purpose


  This class implements a "density plane", ie a representation of 2-D
  numeric data on a flat surface using colour or grey-scale
  density. A rectangular array of cells (quadrilaterals) is set out
  and the data values are represented by the colour at the centre of
  the cells (STYLE=0) or at the vertices (STYLE=1).
  This density plot implementation (MDR) uses a rectangular
  IDLgrPolygon with a texture-mapped image. The image has fixed
  dimensions and data are regridded onto it. Compared with
  MGHgrDensityPlane (MDP--an implementation based on an IDLgrSurface
  or an IDLgrPolygon), an MDR is rendered faster (especially on
  large datasets) but takes longer to initialise or to recalculate
  for new data. The other major difference is that missing-data
  cells in an MDR have byte value 0 whereas in an MDP they are
  omitted from the object. The missing-cell behaviour of an MDR
  could be changed using a true-colour, transparent image.
  An MGHgrDensityRect (MDR) is very similar to an MGHgrDensityRect2
  (MDR2), the difference being that in the MDR2 the image is not
  texture-mapped on a polygon. The MDR2 is faster than the MDR but
  doesn't fit well in a 3D environment.

To Do


  Make initialisation more robust: allow DATAX, DATAY and/or DATA_VALUES
  to be initially undefined.
###########################################################################
  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, 1998-09:
    Written, based on earlier density plot implementations.
  Mark Hadfield, 2002-07:
    Now allows a curvilinear horizontal grid via 2-dimensional
    DATAX and DATAY arrays.



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