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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
I have changed the way that VisAD handles missing data and data excluded by SelectRange. Specifically, it no longer destroys topology unless there are actually missing values for RealTypes mapped to spatial DisplayRealTypes (e.g., XAxis, YAxis & ZAxis). Instead, missing or de-selected values now force color=black. This is ambigous with the situation that color is actually black, but I think that users would prefer that ambiguity to displays turning into isolated sets of points. I welcome feedback on this, if anyone disagrees. You can see the change by running 'java DisplayTest 21' in the visad/examples directory. This will not fix the case where a RealType mapped to a spatial DisplayRealType has missing values, since the spatial topology really is destroyed. The workaround here is for applications to explicitly resample data to a new Set which has an intact topology in displayed coordinates. The examples/SatDisplay.java application illustrates this nicely - it reads a McIDAS GVAR area with pixels off the earth and then displays it in earth coordinates. If SatDisplay tried to display the image without resample, the transform to earth coordinates by visad.data.mcidas.GVARCoordinateSystem would create missing latitude and longitude values for off-earth pixels and hence an invalid topology. The resample is done to a Set in earth coordinates (which must have a valid topology in earth coordinates). Thanks to Don Murray of Unidata for the SatDisplay.java application. Cheers, Bill ---------------------------------------------------------- Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI 53706 hibbard@xxxxxxxxxxxxxxxxx 608-263-4427 fax: 608-263-6738 http://www.ssec.wisc.edu/~billh/vis.html
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