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Asked by AP
on 28 Oct 2012

Dear All,

I have generated a vector field in 3D. the coordinates are created by meshgrid. Now I need to rotate the domain 90° about y-axis. When I do this and try to plot the isosurface of some values, I get the following error:

Input grid is not a valid MESHGRID.

How can I solve this problem?

Thanks,

Ahmad

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Answer by Matt J
on 29 Oct 2012

You can't perform a coordinate transformation on a meshgrid and still expect it to be a meshgrid. Only certain transforms like translations preserve a mesh. Use griddata or TriScatterdInterp to obtain gridded samples.

Walter Roberson
on 29 Oct 2012

90 degree rotations around the z axis would also preserve the grid structure.

Matt J
on 29 Oct 2012

It would still form a lattice, but the new x-coordinates would not be monotonically increasing.

Walter Roberson
on 29 Oct 2012

isosurface() requires that the X and Y be monotonic, not that they be monotonic increasing.

## 3 Comments

## Image Analyst

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/52124#comment_107884

By using the debugger?

## AP

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/52124#comment_107906

This is the error message that I get in Matlab.

## Matt J

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/52124#comment_107928

How are you performing the rotation? A 90 degree rotation about y should transform (x,y,z) to (z,y,-x). Are you doing this formula directly, or are you using trigonometric functions to generate rotation matrices? If you are using trig functions are you using COS & SIN or are you using COSD & SIND ?