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Re: Polar to spherical coordinates
- Subject: Re: Polar to spherical coordinates
- From: Patrick Ford <pford(at)bcm.tmc.edu>
- Date: Thu, 27 Apr 2000 21:30:14 -0500
- Newsgroups: comp.lang.idl-pvwave
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- References: <firstname.lastname@example.org> <MPG.email@example.com>
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- Xref: news.doit.wisc.edu comp.lang.idl-pvwave:19433
Oh, if what I wanted was that easy. What I would like is more akin to
the MAP_IMAGE function. I want to convert a 2D array "image" into a 3D
array "image" such as a polar projection to a sphere ( 3D array) and
back again. Using the WHERE function and the CV-COORD function I have
partially done what I need to do. It looks like I will need to create
a look-up-table (LUT) to translate the coordinates.
It still seems like there must be a trivial solution other than to
create a LUT and its inverse. I vaguely recall from some math-sci
course I took in college 20 or so years ago that we used transform to
"transform" from one domain to another. This is what I am looking for,
a function that will do this transform. If I make one, I will post it
so that it will be decreased in size by 80% and speed by 300% as usual
since I still think in FORTRAN or C and not IDL.
In article <MPG.firstname.lastname@example.org>, David Fanning
> Patrick V. Ford (email@example.com) writes:
> > I have a problem that is screaming at me that there must be a simpler
> > solution in IDL than I have devised. I am attempting to relearn IDL,
> > after months of being away from it, and the math after decades from it and
> > I have not found a built-in procedure that does the trick.
> > The problem in its, simplest form, is that I want to take a 2-D polar
> > plot and transform it into a 3-D hemisphere and vice versa. More
> > accurately, a polar plot to a 3-D hemi-ellipsoid with varying axes and
> > thickness, i.e. more than just a surface plot. The manner that I am
> > thinking how to do this is to sample the polar plot along its radius and
> > map it to the hemisphere(with for loops). It seems to me that this is
> > likely common in IDL to map from polar to spherical coordinates and to
> > warp shapes. Since I don't wish to reinvent the wheel, and not a good
> > wheel at that, I would appreciate being pointed in the right direction.
> I'd start by trying to use CV_COORD to map from polar to
> spherical coordinates.