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On Mar 24, 4:40*am, broli <Brol...@gmail.com> wrote:
> hello i am trying to implement a hald edge data structure.
>
> In my project, I have to read a file that contains the geometrical
> specifications of a 3d object which has been converted into a
> triangular mesh. I have specified the format of the file in a previous
> thread -
>
> http://groups.google.co.in/group/com...f95654400d414d
> (ignore the program bit just read about the format of file)
>
> ^^ I have stored all this information in a vertex list. Sequentially
> in the way they occur. After the coordinates, the file specifies 3
> indices into the vertex list(which point to 3 vertices) needed to
> define a triangle.
>
> Now I'm successfully able to code a program read the data from the
> file
> with the help of data structures that I created for vertex, object and
> But now, I want to implement adjacency queries for which I need half
> edge data structure. I do not understand how to create a half edge
> data structure from this plethora of information (i.e. vertex list and
> triangle list). I looked on *flipcode and found some information about
> the structures involved -
>
> * struct HE_edge
> * * {
>
> * * * * HE_vert* vert; * // vertex at the end of the half-edge
> * * * * HE_edge* pair; * // oppositely oriented adjacent half-edge
> * * * * HE_face* face; * // face the half-edge borders
> * * * * HE_edge* next; * // next half-edge around the face
>
> * * };
>
> * struct HE_vert
> * * {
>
> * * * * float x;
> * * * * float y;
> * * * * float z;
>
> * * * * HE_edge* edge; *// one of the half-edges emantating from the
> vertex
>
> * * };
>
> * *struct HE_face
> * * {
>
> * * * * HE_edge* edge; *// one of the half-edges bordering the face
>
> * * };
>
> Now my main question : How do I fit all this data into the structures
> above ?? Do I need to loop through each vertex in the vertex list and
> each triangle in triangle list ??

You want news:comp.graphics.algorithms.algorithms (especially since I
see that elsethread you are asking about efficiency).