| Re: Polar to spherical coordinates [message #19911 is a reply to message #19807] |
Thu, 27 April 2000 00:00  |
Patrick V. Ford
Messages: 14
Registered: February 1997
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Junior Member |
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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.
Thanks
In article <MPG.136e22dd5bfafe0c989aeb@news.frii.com>, David Fanning
<davidf@dfanning.com> wrote:
> Patrick V. Ford (pford@bcm.tmc.edu) 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.
>
> Cheers,
>
> David
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