Is the given data obj correct?

[xuzheng0927]

I am looking at the very simple quad_mesh object and found something weird. In the picture, when calculating cotan values of vertex i, the vertex of angle beta acquired by using mesh.to_vertex(mesh.next_halfedge(e_ij)) is on the upper-left corner, which does not have an edge connected to vertex i at all. That makes it impossible to get the right laplacian beltrami matrix. The woody object is too big to check, so is it possible this data file also has the same issue?

[nlguillemot]

I manually consulted the meshed_quad.obj file, and the obj file itself doesn't look wrong.

[xuzheng0927]

So for every half edge of vertex i, the vertices alpha and beta should be connected to vertex i, right? But I got the following output:

calculating vertex 0
p_i: 0.5,-0.5,0
p_j: -0.5-0.5,0
p_b: -0.5,0.5,0
p_a: 0,0,0

There is no edge between p_i and p_b. What could be wrong? Toooo confused.

[xuzheng0927]

I used the mesh_laplacian_cotangent.m in Dropbox and got this result (same as my manual calculation):

-2,0,0,0,2
0,-2,0,0,2
0,0,-2,0,2
0,0,0,-2,2
2,2,2,2,-8

The result got from the github code (should be wrong because vertex 0~4 only have 3 edges):

-4 1 0 1 2
1 -4 1 0 2
0 1 -4 1 2
1 0 1 -4 2
2 2 2 2 -8

Is it possible that the mesh.next_halfedge function has something wrong?

[nlguillemot]

It would be really really weird if mesh.next_halfedge had a bug since it's been used for so long.

[xuzheng0927]

Ok, then I'll need to write a function not using mesh.next_halfedge and see
if the result can be different.

On Thu, Nov 17, 2016 at 11:49 PM, Nicolas Guillemot <
notifications@github.com> wrote:

It would be really really weird if mesh.next_halfedge had a bug since
it's been used for so long.

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