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Subject: Re: Interpolation to arbitrary plane through 3D image / decimal truncation issue
Date: Sun, 20 Jun 2010 16:14:05 +0000 (UTC)
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"Yngve Munck-Lindblom" <yngvechr@fys.ku.dk> wrote in message <hvkqa1$n96$1@fred.mathworks.com>...

> But a specific problem: The image frame coordinates are projected onto the RCS axes and by this they lose the perfect linearity normally gained by using linspace making interp3 complaining about my coordinates not being produced by meshgrid. They're very close to being linear (only differences in the last three decimals for double precision numbers). It's yet another numerical thing.
===================

Sounds like you are passing your coordinates to the wrong function arguments. When you call interp3 as follows

interp3(X,Y,Z,V, XI,YI,ZI)

it is X,Y,Z that must be plaid/monotonic, as if produced by meshgrid. However, your projected coordinates should be passed to XI,YI,ZI. There is no such requirement on them.