CGAL users discussion list

[thierry Fernandez <>]

if you want to use alpha_shape for 3d coplanar points, make as follow:

take your plane equation : ax+by+cz=d

compute d=sqrt(a^2+b^2+c^2).

so vector N(a/d,b/d,c/d) is a normalized vector pependicular to your plane.

you have to compute vector u0 = cross product(N,k) and normalize it

pay attention if N and k are colinear compute u0 = cross product(N,i)

now compute v0 = cross product(N,u0) and normalize it.

Now for each 3D point P3 of your plane compute a 2D point P2:

first compute a vector v = P3 - [dot product(P3,N)] N

now P2 x = dot product(v,u0) and P2y=dot product(v,v0)

2015-03-14 14:17 GMT+01:00 cgaljunior <>:

My apologies, but i didn`t get your answer.

i looked for changement basis in CGAL 4.5.X/4.6 but couldn`t find anything
relevant.

Appreciate if you could be more specific.

Best Regards,
Igor



--
View this message in context: http://cgal-discuss.949826.n4.nabble.com/Algorithm-to-extract-approximating-polygon-tp4660582p4660584.html
Sent from the cgal-discuss mailing list archive at Nabble.com.

--
You are currently subscribed to cgal-discuss.
To unsubscribe or access the archives, go to
https://sympa.inria.fr/sympa/info/cgal-discuss