CGAL users discussion list

[Bo Zhou <>]

 wrote:
> I am a student and would like to learn more about CGAL, but I'm having
> difficulties. 
> according to the example:  demo/Convex_hull_3/incremental_hull_3_demo.cpp 
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> int main ()
> {
>   Convex_hull_3 CH(3);  // create instance of the class with dimension == 3
>
>   // generate 250 points randomly on a sphere of radius 100
>   // and insert them into the convex hull
>   CGAL::Random_points_in_sphere_3<Point_3, Creator> gen(100);
>
>   for (int i = 0; i < 250 ; i++, ++gen)
>      CH.insert(*gen);
>   assert(CH.is_valid());
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
>   Point_3 p(int x,int y,int z);
>   CGAL::Random_points_in_sphere_3<p, Creator> gen(100);
>
> the above statement is wrong, how to implement????
>
>
> I would like to generate points for two balls, but he always puts the points 
> in
> origin. So d would include the items in the coordinates (x, Y, Z) that I set. 
>
> how make? 
>
> thaks!
> Leandro
>   
Hello,

You should consider the point set on sphere generated by CGAL is in a 
*Local Coordinates.* If you want to generate to separated two balls, you 
should translate the points on sphere by multiply a translate matrix in 
order to "move rotate scale" the ball. Take one OpenGL book for more 
information about coordinates transformation.

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