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Topic: Navigating in a rotated grid?
Replies: 3   Last Post: Nov 17, 2010 7:03 AM

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JS

Posts: 49
Registered: 8/4/08
Re: Navigating in a rotated grid?
Posted: Nov 17, 2010 7:03 AM
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> Well, the rotation matrix above seems like the way to go.
> Why is this not a "nice" result?
> Can you provide an example?
> Can you use interp1 (or one of its variations)
> to get your "even" spacing?
>
>
>

> > /JS

Hi,

Thanks for your reply!

Yes, for now I have had to resort to rotating the grid to be "upright"
and interpolate the rotated grid onto a perfect (even-spaced) one with
GRIDDATA. Given the small discrepancies, this interpolation does not
change much, so it is acceptable for now.

An example would be this. Imagine a grid with unit spacing, rotated 10
degrees clockwise thus forming a diamond with the lower left corner
set in (0,0). If I position myself in this left corner (0,0) and I
wish to move to the next point along the lower edge of the grid (to
read off the Z coordinate associated with that point), which in the
"upright" version of the grid would be (1,0), how do I find that point
easily in the rotated grid? Since I know the spacing to be 1, and the
angle to be 10 degrees, I can of course predict the coordinates where
the point should be in the "upright" system and then look for it in
the list. But this just appears to be a clumsy solution. This is the
same as rotating the the entire grid up and handling the uneven
coordinates with some rounding scheme.

But I have now thought about it for a while and I guess there is no
"correct", elegant way of doing this, that is, defining my own
coordinate system, with axes parallel to the grid's edges.

Thanks for looking!

/JS




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