Maths - Conversion Matrix to Axis Angle

By: Vladimir Smutny - smutny
file Matrix to Axis Angle slight correction  
2006-05-10 11:30

Dear Mr. Baker, 
I believe that the Java(?) code on the page 
https://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToAngle/index.htm 
does not reflect sign analysis done in the table. 
When there is some of the vector component close to zero, then sign of the other components depend on the sign of nondiagonal terms which is not reflected in the code. So the relevant part of the code shall probably read instead of  
if (xZero && !yZero && !zZero) y = -y; 
else if (yZero && !zZero) z = -z; 
else if (zZero) x = -x; 
 
but  
if (xZero && !yZero && !zZero)  
if (!yzPositive) y = -y; 
else if (yZero && !zZero) 
if (!xzPositive) z = -z; 
else if (zZero)  
if (!xyPositive) x = -x; 
 
I am not sure about syntax but I am quite positive about the fact (my implementation is in Matlab, so I cannot copy working code). 
 
Best Regards, 
Vladimir Smutny 


metadata block
see also:

 

Correspondence about this page

Book Shop - Further reading.

Where I can, I have put links to Amazon for books that are relevant to the subject, click on the appropriate country flag to get more details of the book or to buy it from them.

cover Introductory Techniques for 3-D Computer Vision by Emanuele Trucco, Alessandro Verri

 

This site may have errors. Don't use for critical systems.

Copyright (c) 1998-2017 Martin John Baker - All rights reserved - privacy policy.