nmwsharp / nonmanifold-laplacian

A robust Laplace matrix for general (possibly nonmanifold) triangle meshes, and point clouds [Sharp & Crane SGP 2020]
MIT License
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Angular sort in tufted cover impacts eigenvalue calculation #4

Open svorderw opened 4 months ago

svorderw commented 4 months ago

Hello!

I have been looking at your project to calculate eigen information on pointclouds. During the construction of the tufted cover there is an angular sorting of the faces around the non-manifold edge. In the corresponding paper you mention that the Laplacian should be robust to the orderings, but I observe a significant difference in the eigenvalues if I compare the construction with and without angular sort. The difference is shown in the following picture.

image

I have produced a "minimal failing example" for reproducibility on a branch. The branch contains the addition of the Eigensolver and a control for the sorting. If you give me access rights, I can push the branch to your project, and you can try it yourself.

I was wondering if you had any insight why I observe these differences. Is it a floating-point issue? Is the tufted cover not unique and depends on ordering? @nmwsharp

Many thanks in advance, and let me know if there is a better channel do discuss this, Sophia Vorderwuelbecke

svorderw commented 3 months ago

@sitic