Automatic mesh generation within the context of non-manifold geometric
models is far from a commercial reality. While manifold objects are t
he most commonly encountered domains in many applications, other appli
cations such as those requiring multiple material models and mixed-mod
el representations (combinations of 1-D, 2-D and 3-D domains) fall bey
ond the realm of the existing automatic meshing procedures as they req
uire a non-conventional modeling environment, namely the non-manifold
topology (NMT) based environment. This paper focuses on automatic mesh
generation issues in the context of two such applications. (i) finite
element modeling for multiple material models and (ii) geometric abst
ractions requiring a mixed-model representation. Specifically, the pap
er describes a geometry utility system, built around an NMT data struc
ture and geometry-based meshing algorithms that ensure the validity of
the mesh for non-manifold domains.