CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 04/23/2014 03:39 AM, Ivan Middleton wrote:
> I was just comparing the results of CGAL's implementation of Loop
> subdivision with my own implementation, and found a very bad error in CGAL.
>
> On line 240 of include/CGAL/Subdivision_mask_3.h we find:
>
> FT Cn = (FT) (5.0/8.0 - std::sqrt(3+2*std::cos(6.283/(double)n))/64.0);
>
> The square root should instead be a squaring operation! (A much more
> minor point is that it surely wouldn't hurt to use a more accurate value
> for 2pi.)
>
> This number Cn is what's called beta (or n*beta) in most references. See
> for instance page 70 of
>
> http://mrl.nyu.edu/publications/subdiv-course2000/coursenotes00.pdf
>
> Best regards,
> Ivan

Thanks for the report, it will be fixed in the next release of CGAL.


Best,

Sebastien.