how to draw a tilted circle?

Question

bsd 2011-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/17361-how-to-draw-a-tilted-circle

Hai,

The following code draws a circle in the x-z plane in 3D.

radius=1;
center=[2 4 2];
theta=linspace(0,2*pi);
rho=ones(1,100).*radius;
[x,z]=pol2cart(theta,rho);
x=x+center(1);
z=z+center(3);
y=center(2)*ones(1,length(x));
figure;
h=plot3(x,y,z);
grid on;
axis square;

By default the above circle is vertical in the x-z plane. I need to draw a circle which is inclined or tilted at some angle. How could I do this?

Looking forward for your reply.

BSD

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Walter Roberson 2011-10-3

Duplicate is at http://www.mathworks.com/matlabcentral/answers/17160-how-to-draw-an-inclined-circle

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Answer 1

Jan 2011-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/17361-how-to-draw-a-tilted-circle#answer_23419

在 MATLAB Online 中打开

You have X-, Y- and Z-coordinates. Now you want to tilt the obejct. This can be done by applying a rotation matrix, e.g. for a rotation around the Z-axis by the angle a :

R = [ cos(a), sin(a), 0; ...
     -sin(a), cos(a), 0; ...
      0,      0,      1];

This matrix must be multiplied to the array of coordinates. See also: Wiki: Rotation Matrix

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Walter Roberson 2011-10-4

Generate the circle around (0,0,0), rotate it, and then translate the circle by the coordinates of the new center that you want.

Or if you already have a circle existing and decide later that you want to tilt it, then translate it to (0,0,0), rotate it, and then translate it back.

bsd 2011-10-5

It is working. Excellent... Thank you...

BSD

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Answer 2

Walter Roberson 2011-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/17361-how-to-draw-a-tilted-circle#answer_23414

The answer hasn't changed since your previous time asking.

If you wish to do it mathematically instead of the way I suggested before, then say as much (at which point I would say, "So, did you read the documentation to find out what that routine actually does ?")