On 2010-04-20 08:23-0700 David MacMahon wrote: > Hi, Maurice and Alan, > > On Apr 20, 2010, at 0:39 , Maurice LeBrun wrote: > >> The general remapping of coordinates is a crucial part of it. > > I think you are referring to the 0/2pi coordinate "seam" when transforming a > rectilinear grid to a polar grid.
I should emphasize for my simple test case that theta(x,y) = arctan2(y, x) is the function you are contouring on a rectilinear x, y grid, and that no remapping of coordinates away from an x, y coordinate system is desired. So the question is whether there is a practical way with our current API to contour that simple test case without the contours going crazy at the discontinuity? I believe the answer is (although I am not completely positive since I have never tried it) the user-defined transformation function could simply interpolate the grid of theta values in x and y without doing any coordinate transformation but demand local continuity of theta by adding or subtracting 2 pi when necessary. And similarly for the more general case described by Ed. BTW, if somebody believes my idea for proper contouring of the simple test case would work and is willing to implement it, then that would make a nice additional page for example 9 to refer to if this topic ever comes up again. Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); PLplot scientific plotting software package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________ ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Plplot-devel mailing list Plplot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/plplot-devel
