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View Full Version : How to draw an ellipsoid with arbitrary axes?



dolphinmark
11-10-2003, 06:34 PM
Hi,
I'm new to Opengl. Now I have a problem. I dont know how to draw an ellipsoid with arbitrary axes. Now I know three vectors indicating three directions of the axes of the ellipsoid. I also know the lengths of each axes and the center of the ellipsoid. How can I draw such an ellipsoid?
Thank you very much!

--dolphin mark

gator
11-10-2003, 07:25 PM
Does GLU draw quadratics or this kind of stuff? I know it does torus, sphere, etc...

To draw any surface you can think of, all you need are the x,y,z parametric equations
that describe it. So, do a search for them.

[This message has been edited by gator (edited 11-10-2003).]

dolphinmark
11-10-2003, 07:32 PM
I think I can draw a sphere first. Then translate, rotate and scale it to an ellipsoid. But I don't know how to rotate three axes of the current coordinate to arbitrary three orthogonal axes.
Can anyone help me?
Thanks a lot!

gator
11-10-2003, 09:40 PM
I think you need to lookup matrix transformations. If it's an orthogonal matrix, the
columns or rows of matrix should contain the x,y,z axis system. You can use this bit of
info to create a specific local to world matrix transformation.

Then after getting your matrix, it's a matter of multiplying every vertex by it.