This study aims to achieve two interrelated goals:
first, to rigorously elucidate the theoretical
foundations of classical differential formulations, and
second, to systematically assess the computational
efficiency and geometric fidelity of discrete curvature
quantification. The investigation relies on three
methodological pillars: a detailed analysis of
curvature integration principles in smooth manifolds,
an exploration of vertex-centric summation
techniques for triangulated surfaces, and a
comparative framework delineating the similarities
and differences between these approaches. By
synthesizing these perspectives, the research seeks to
clarify how discrete methods balance computational
feasibility with abstract geometric-topological
relationships, ultimately fostering optimized
frameworks that maintain critical invariants and
bridge theoretical concepts with real-world
applications.
2 LITERATURE REVIEW
The shift from local analysis to global topological
research in differential geometry was marked by
Chern's (1944) groundbreaking intrinsic
demonstration of the Gauss-Bonnet theorem via fiber
bundle theory. This not only unified the relationship
between curvature integrals and the Euler
characteristic but also highlighted the deep
connection between topology and manifold
geometry. For example, topological invariants such
as Pontryagin classes have a direct relationship with
manifold structures (Besse 1987). However, Chern's
proof relies on the smoothness of manifolds, making
it inapplicable to discrete or irregular structures like
triangular meshes or complex networks commonly
used in computer graphics.
This limitation spurred the development of
discrete differential geometry. Thurston's (1980)
angle defect model, for instance, simplified curvature
computations by summing angles around vertex
neighborhoods, ensuring that discrete curvature on
triangulated surfaces complies with the global
topological constraints of the Gauss-Bonnet theorem.
Despite this advancement, discrete methods remain
highly sensitive to grid quality, as emphasized by
Hildebrandt et al. (2006). Poor grid quality,
especially near non-uniform triangulations or
singularities, can introduce significant errors. This
challenge was further underscored in Wardetzky et
al.'s (2007) analysis of discrete Laplace operator
convergence, which showed that while discrete
curvature may converge to continuous values in
smooth regions, errors can exceed 20% in high-
curvature areas such as conical vertices.
The fundamental distinction between classical
differential methods and discrete graph-theoretic
approaches lies in their mathematical tools. Chern
(1944) and Milnor (1963) employed differential
forms, covariant derivatives, and fiber bundle theory,
with the core idea being the integration of local
differential data to capture global topological
information. For example, on compact Riemannian
manifolds, the integral of Gaussian curvature equals
exactly 2πχ, a result used in general relativity to prove
the topological rigidity of certain spacetime
manifolds (Gallot et al. 1990). However, the
computational cost of this continuous framework is
high, and it is difficult to adapt to digital modeling
needs. In contrast, discrete methods redefine
curvature using topological and graph-theoretic tools
like simplicial complexes and adjacency matrices.
Meyer et al.'s (2003) discrete exterior calculus
(DEC), for example, transforms curvature
computation into linear algebra operations, making
the processing of complex surfaces several orders of
magnitude more efficient. Bobenko and Suris (2008)
caution, however, that discrete methods are
inherently approximate: under non-flat metrics, angle
defects only approximate continuous curvature, with
accuracy limited by grid resolution. Springborn et al.
(2008) partially addressed this in their study of
discrete conformal geometry, proving that optimizing
edge weight distributions in triangulations can make
discrete curvature precisely match the theoretical
values of continuous conformal structures. This
improvement, however, introduces nonlinear
optimization problems that significantly increase
computational complexity.
Despite the advantages of both methods, existing
research reveals three key gaps. First, although
classical and discrete approaches have been
extensively explored within their respective domains
(Crane et al. 2013; Gu and Yau 2008), few studies
directly compare their computational accuracy and
topological fidelity on identical geometric objects.
Polthier and Schmies's (1998) Voronoi correction
method reduces discrete curvature errors, but its
effectiveness has only been verified on 2D surfaces,
with higher-dimensional extensions still
inconclusive. Second, Banchoff (1967) attempted to
extend the discrete Gauss-Bonnet theorem to 3D
manifolds but found that additional constraints, such
as combinatorial conditions for dihedral angles in
tetrahedra, were required, drastically increasing
theoretical complexity and computational cost. This
contrasts with Regge's (1961) discrete general