Tessellate a plane of points
===

I have a file filled with 3d points. The points form a plane. Here is an example file:

    25
    1 -1 0
    1 -0.5 0
    1 0 0
    1 0.5 0
    1 1 0
    0.5 -1 0
    0.5 -0.5 0
    0.5 0 0
    0.5 0.5 0
    0.5 1 0
    0 -1 0
    0 -0.5 0
    0 0 0
    0 0.5 0
    0 1 0
    -0.5 -1 0
    -0.5 -0.5 0
    -0.5 0 0
    -0.5 0.5 0
    -0.5 1 0
    -1 -1 0
    -1 -0.5 0
    -1 0 0
    -1 0.5 0
    -1 1 0

This file states that there are 25 points in the plane, and lists the points. The points are regularly spaced. Based on this information, how could I form triangles out of the point data and store it in a `std::vector<Tri>` where `Tri` is a

    struct Tri 
    {
      double x, y, z;
    };