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Index › Programming Questions & Help › OpenGL and 3D Libraries › calculating the axis of rotation
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calculating the axis of rotation (Read 764 times)
Henrik
calculating the axis of rotation
Apr 12th, 2006, 12:42pm  
Hello,
As my brain is starting to smoke, and google cant seem to give me an understandable answer, turn to you for a possible solution.
my problem is as follows:
I have a point defined in polar coordinates (Zrotation, Yrotation and distance), now i need to find out what the absolute rotation is, by that i mean a single rotation around a defined axis that returns the same point in space.
I've been speculating that this angle is sqrt(Zrotation^2 + Yrotation^2) but i havent been able to verify this. Is there anyone out here that have a better understanding of this than me? also i would like to know how to calculate the axis of this rotation.
hope my explanation is understandable:

regards

Henrik
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JohnG
Re: calculating the axis of rotation
Reply #1 - Apr 13th, 2006, 12:24pm  
You can get the axis of rotation by doing a cross product of the original vector (0 rotation, but some distance) and the resultant vector (after the y/z rotations), but you'll have to convert from polar to cartesian co-ordinates.
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Henrik
Re: calculating the axis of rotation
Reply #2 - Apr 13th, 2006, 4:28pm  
Thanks again my geometric friend!
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Henrik
Re: calculating the axis of rotation
Reply #3 - Apr 14th, 2006, 2:54pm  
btw, to get the combined angle, is the formula totalAngle = sqrt(zAngle^2 + yAngle^2) correct?

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JohnG
Re: calculating the axis of rotation
Reply #4 - Apr 14th, 2006, 3:48pm  
I don't know.. but it looks like it should work... Test it and see Smiley
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