A method for the approximation of the three principal curvatures at po
ints on a discretized, triangulated 3D manifold in 4D space (referred
to as 3-surface) is presented. The approximation scheme is based on th
e fact that a parametric 3-surface can locally be approximated by the
graph of a trivariate function. Using a local coordinate system, a lea
st square polynomial approximation is constructed for the estimation o
f the principal curvatures at each 3-surface point. Curvature is extre
mely useful for the analysis of qualitative characteristics of surface
s. The technique presented is an example of extending existing surface
interrogation methods to multivariate data. Such a generalization is
valuable for scientific visualization.