The Associated Discrete Laplacian in $\mathbb{R}^3$ and Mean Curvature with Higher order Approximations

Abstract: In $\mathbb{R}^3$, the primal and dual constructions yield completely different discrete Laplacians for tetrahedral meshes.In this article, we prove that the discrete Laplacian satisfies the Euler-Lagrange equation of the Dirichlet energy in terms of the associated discrete Laplacian corresponding to the dual construction. Specifically, for a three simplex immersed in $\mathbb{R}^3$, the associated discrete Laplacian on the tetrahedron can be expressed as the discrete Laplacian of the faces of the tetrahedron and the associated discrete mean curvature term given by the ambient space $\mathbb{R}^3$. Based on geometric foundations, we provide a mathematical proof showing that the dual construction gives a optimal Laplacian in $\mathbb{R}^3$ compared to the primal construction. Moreover, we show that the associated discrete mean curvature is more sensitive to the initial mesh than other state-of-the-art discrete mean curvatures when the angle changes instantaneously. Instead of improving the angular transient accuracy through mesh subdivision, we can improve the accuracy by providing a higher order approximation of the instantaneous change in angle to reduce the solution error.