Abstract:
We present a set of interactive, free-form editing operators for direct
manipulation of level-set models that supports the creation and removal
of surface detail. The mathematics, data structures and algorithms needed
to implement numerous level-set modeling capabilities have been developed.
The first component of these capabilities identifies the
Region-of-Influence (ROI) on the surface to be modified, and the
specification of user handles, i.e. a point or a curve within the ROI,
that are used to control the free- form surface edits. The editing
operators include pulling the level-set surface by a handle with the
surface changes occurring symmetrically around the handle or within
the ROI, surface offsetting and carving, deformations towards a profile
curve and localized smoothing. The editing operators are implemented
with specialized speed functions, which are incorporated into the level
set partial differential equation (PDE). The PDE is then evolved to
produce the desired model modification. The specific form of each speed
function is described in detail. The operators have been combined with
an OpenGL interface and the VISPACK level-set library to create a
preliminary interactive level-set modeling system. VISPACKâ's narrow-band
data structures have been extended to localize all computations and
updates to optimize running time and provide interactive performance.
Additional sketch-based level-set editing operators have been implemented
within the system, and are described elsewhere. A variety of level-set
models are presented to demonstrate the effectiveness of the editing
operators.
