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find a cell from its centroid coordinates

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Old   March 2, 2018, 03:34
Default find a cell from its centroid coordinates
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annan
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Dear all,

Does anyone know how to find a cell when its centroid coordinates are known ?
I have the coordinates x[0] and x[1], and I want to find the corresponding cell in my UDF

Thank's a lot
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Old   March 2, 2018, 09:30
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Doruk Yelkenci
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Hi Annan;

Here is how I would do it. I hope it gives you the idea.

real a,b;
int i;
real x[N_D];

begin_c_loop (c,t)
{
C_CENTEROID(x,c,t);
if(x[0]>a-0.00001 && x[1]>b-0.00001 && x[0]<a+0.00001 && x[1]<b+0.00001) // a and b are the coordinate values
{
i=c;
}
}
end_c_loop(c,t)

I dont know if the +-0.000001 (just a small value) would be able sufficient to find the cell you can work on it for your case. Ansys gives error if commands have real=real.

In the end the integer "i" will be the number of the cell you are looking for.

Best Regards,
Doruk
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Old   March 5, 2018, 06:36
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Hi Annan,

doruk's solution should work (in serial and 2D, but easily fixed to work in 3D). It is currently only a sketch -- for example, you would probably want a thread loop for all values of t. But this is clearly an O(N) process, where N is the number of cells.

A more efficient algorithm is available built-in, but the syntax is slightly fiddly and version-dependent -- google for CX_Find_Cell_With_Point, for example CX_Find_Cell_With_Point: problem.

Good luck!
Ed
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