CGAL users discussion list

[杨成林 <>]

Hello Alliez,

Thanks for your immediate response.
In the PCA component,users can only get the eigenvector corresponding
to the largest eigenvalue in line-fitting or the eigenvector
corresponding to the smallest eigenvalue in plane-fitting.The other
eigenvectors seem to be inaccessible,though they are also very useful.

2009/2/13 Pierre Alliez 
<>:
> Hello wildabc (I was unable to recover your first name from your email,
> hence I take your gmail adress),
>
> Many thanks for sending feedback on this bug - I will double check this and
> correct it as soon as possible. Should you have any other suggestions I
> would be pleased to improve the PCA component as well.
>
> best regards,
>
> Pierre Alliez
> INRIA Sophia Antipolis - Mediterranee Project-team GEOMETRICA
> http://www-sop.inria.fr/members/Pierre.Alliez/
> Tel: +33 4 92 38 76 77
> Fax: +33 4 97 15 53 95
>
>
>
> 杨成林 a écrit :
>>
>> Hello
>>
>> I am new to CGAL.I use  linear_least_squares_fitting_3 to estimate
>> normals from point-cloud.But it can't give correct results
>> sometimes.After examining the source code,I think line 709-710 in
>> PCA_util.h(CGAL 3.4) may be incorrect.
>>
>> eigen_values[2] is the smallest eigenvalue,so "eigen_values[2] ==
>> eigen_values[1]" means Degeneracy."eigen_values[0] == eigen_values[1]"
>> just means the points distribute isotropically in the plane,but the
>> fitting plane exists uniquely.
>>
>> I change this two lines to "if(eigen_values[2] != eigen_values[1])".It
>> works well.
>>
>
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