CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

On 09/23/2014 04:43 PM, vahid wrote:
> Actually, what I want to do is to project the query point on the
> surface, and use the closest point on the surface to distribute some
> information from the query point to the nodes of the closest triangle.
> My question specifically is that when CGAL returns the coordinates of
> the vertices of the triangle which includes the closest point, how can I
> find out the ID numbers of the vertices. For instance, if my surface has
> thousands of vertices and triangles, and I have found the closest point
> on the surface with the triangle that passes through that point, how can
> I find out the ID numbers of the vertices constructing that triangle
> (instead of their coordinates). That means if I call points a, b, c, d,
> etc as points 1, 2, 3, 4, ... then is there any way for CGAL to give me
> the ID number of the three vertices making the closest triangle (such as
> points 1, 2, and 4)?
> Thanks,
> Vahid

What you have as input is a soup of triangles (that is with no 
relationships with each other). So there is even no notion of
vertices for the whole set of triangles.

What you can easily get is the id of the triangle (since the 
closest_primitive() function will return the iterator corresponding
to the input triangle). Provided you have you own way to index
vertices from a triangle id, then you can associate your information.

Sebastien.

> On Tue, Sep 23, 2014 at 3:52 AM, Sebastien Loriot (GeometryFactory) [via
> cgal-discuss] <[hidden email]
> </user/SendEmail.jtp?type=node&node=4659884&i=0>> wrote:
>
>     On 09/22/2014 09:58 PM, vahid wrote:
>
>     > Thank you so much Sebastien for your help.
>     >
>     > I can get the vertex coordinates of the closest triangles by using:
>     > std::cerr << "closest primitive is: " << *closest_primitive << 
> std::endl;
>     > which gives me the coordinates of all the three vertices constructing 
> the
>     > triangle, consecutively. How can I get the location of the points 
> separately
>     > instead of having them all together? (I guess it is an easy process, 
> but I
>     > am a beginner in both CGAL and C++) .
>     >
>     > My other question is that then how can I know which points are involved 
> with
>     > this triangles? I mean in the same example, is there a way so I can 
> know for
>     > instance points a,b, and d are the ones that are making the closest 
> triangle
>     > to the query point without performing a search among all the points?
>     >
>     The closest point is a point that is not necessarily a triangle vertex,
>     it is the closest points on the set of triangles provided.
>
>     If you want to perform nearest neighbors queries, you should use this
>     package:
>
>     
> http://doc.cgal.org/latest/Spatial_searching/index.html#Chapter_dD_Spatial_Searching
>
>     Sebastien.
>
>      > Vahid
>      >
>      >
>      >
>      > --
>      > View this message in context:
>     
> http://cgal-discuss.949826.n4.nabble.com/The-triangle-closest-to-a-query-point-tp4659854p4659870.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
>
>
>
>
>     ------------------------------------------------------------------------
>     If you reply to this email, your message will be added to the
>     discussion below:
>     
> http://cgal-discuss.949826.n4.nabble.com/The-triangle-closest-to-a-query-point-tp4659854p4659874.html
>
>     To unsubscribe from The triangle closest to a query point, click here.
>     NAML
>     
> <http://cgal-discuss.949826.n4.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml>
>
>
>
>
>
> --
>
> Vahid Abdollahi
>
> PhD Candidate
> CFD Lab, Mechanical Engineering Department
> McGill University, Montreal, QC, Canada
> Phone: (+1) 514 8051374
> [hidden email] </user/SendEmail.jtp?type=node&node=4659884&i=1>
>
> ------------------------------------------------------------------------
> View this message in context: Re: The triangle closest to a query point
> <http://cgal-discuss.949826.n4.nabble.com/The-triangle-closest-to-a-query-point-tp4659854p4659884.html>
> Sent from the cgal-discuss mailing list archive
> <http://cgal-discuss.949826.n4.nabble.com/> at Nabble.com.