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Plotting Generalized Curves
We have seen how geodesic curves and grid lines can be drawn. The Plot
class includes another method,
AST_GENCURVE,
which allows curves of any form to be drawn. The caller supplies a
Mapping which maps offset along the curve33 into the
corresponding position in the current Frame of the Plot.
AST_GENCURVE,
then takes care of Mapping these positions into graphics coordinates. The
choice of exactly which positions along the curve are to be used to
define the curve is also made by
AST_GENCURVE,
using an adaptive algorithm which concentrates points around areas where
the curve is bending sharply or is discontinuous in graphics coordinates.
The IntraMap class may be of particular use in this context since it allows
you to code your own Mappings to do any transformation you choose.
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AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 210
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2009 Science \& Technology Facilities Council