ylfink@water.waterloo.edu (ylfink) (07/16/88)
DEPARTMENT OF COMPUTER SCIENCE
UNIVERSITY OF WATERLOO
SEMINAR ACTIVITIES
COMPUTER GRAPHICS SEMINAR
- Monday, July 18, 1988
Mr. Dave Forsey, a graduate student of this department,
will speak on ``Hierarchical B-Spline Refinement''.
TIME: 3:30 PM
ROOM: DC 1302
ABSTRACT
Refinement is usually advocated as a means of gaining
finer control over a spline curve or surface during
editing. For curves, refinement is a local process.
It permits the change of control vertices and
subsequent editing of fine detail in one region of the
curve while leaving control vertices in other regions
unaffected. For tensor-product surfaces, however,
refinement is not local in the sense that it causes
control vertices far from a region of interest to
change as well as changing the control vertices that
influence the region. However, with some care and
understanding it is possible to restrict the influence
of refinement to the locality at which an editing
effect is desired. We present a method of localizing
the effect of refinement through the use of overlays,
which are hierarchically controlled subdivisions. We
also introduce two editing techniques that are
effective when using overlays: one is direct surface
manipulation through the use of edit points and the
other is offset referencing of control vertices.