# Orientation of ellipsoid

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Sakshi on 13 Jun 2011
Commented: Amin Ataei on 18 Dec 2020
Hello, I am using ellipsoid function to represent an ellipsoid graphically. The input list requires me to enter the coordinates of the centre of ellipsoid and its semi-axes. There is no input for the orientation of the axis of the ellipsoid with respect to the coordinate system. Is there any way, this can be incorporated if my ellipsoids are at angle with respect to x, y and z axis.

Matt Fig on 13 Jun 2011
See the help for the ROTATE function.
For example:
[x, y, z] = ellipsoid(0,0,0,5.9,3.25,3.25,30);
S = surfl(x, y, z);
colormap copper
axis equal
xlabel('X')
ylabel('Y')
zlabel('Z')
pause % Push return to see the rotation take place.
rotate(S,[0 0 1],45)
Amin Ataei on 18 Dec 2020
after rotation the ellipsoid , how can we check if a given point with its coordinante(x,y,z) is inside of ellipsoid.
If ellipsoid is oriented in main axes we can use the equation from ellipse also :
(x/a)2 + (y/b)2 + (z/c)2 < 1 point is inside ellipsoid
(x/a)2 + (y/b)2 + (z/c)2 > 1 point is not inside ellipsoid
but how can we check the point when ellipsoid is rotated? in this case are all point of ellipsoid rotated and we can not use upper equation anymore , right?

### More Answers (1)

You can generate an ellipsoid with the ellipsoid function and while plotting you can use the rotate() suggest by Matt.It should help you.