CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 11/07/2014 10:16 AM, hmzhangmin wrote:
> Hi Sebastien,
>
> Thanks very much for your reply.
> I have read the document just now.
>
> In my understanding, we can construct an AABB tree for the mesh which we
> generated for a 3D surface, then we can call
> AABB_tree::closest_point_and_primitive which takes the point of each vertex
> as input. Now we get a Point_and_primitive_id object, the returned point
> will have the same coordinates with the input point, because all the vertex
> in a triangle mesh lies on the original 3D surface.
> Also a primitive ID is returned, from this ID we know the facet which just
> contains the input vertex.
>
> So, we still don't know the u/v parameter of each vertex in the original
> surface.

Maybe I don't get what you mean by u/v. I though it was the parametric 
coordinates on the original surface (given a parametrization of the 
original surface). If you have a points on the original surface then you 
get the u/v.

Sebastien.

> In OpenCascade, we can call a function to generate triangle mesh for a 3D
> surface, the result contains an array which stores coordinates for all
> vertexes, it also contains an array which stores all the u/v parameter pair
> for all vertexes.
>
> I'm not sure whether my understanding is right or not, please correct it
>
> Thanks very much,
> Min
>
>
>
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