Vincent CHEUTET1,2, Jean-Philippe PERNOT1,2, Jean-Claude LEON1, Franca GIANNINI2, Bianca FALCIDIENO2
1 : Laboratory 3S
Integrated Design Team
38034 Grenoble
France
e-mail: [vincent.cheutet, jean-philippe.pernot, jean-claude.leon]@hmg.inpg.fr
http://www.3s.hmg.inpg.fr/
2 : IMATI-CNR
16149 Genova
Italy
e-mail: [vincent, jean, giannini, falcidieno]@ge.imati.cnr.it
http://www.ge.imati.cnr.it/
Abstract
Free form shapes are often used
to fulfil both aesthetic and design constraints applied to parametric models currently
adopted in CAD environments. Up to now, designers and engineers have mainly access
either to indirect manipulations of free form surfaces using their control network or
to low-level deformation functions at prescribed points and along a line on a surface.
Based on a study of designers’ activity, a free form deformation feature approach is
proposed to create CAD tools that better fit their way of working. The proposed category
of features aims at enforcing the visual effect of the so-called character lines,
extensively used by designers to specify the shape of an object. For this reason,
in the proposed approach 3D lines are used to drive surface deformation over
specified areas.
One type of these features is based on G0 or G1 discontinuities along the
character lines. Traditionally, a designer using a CAD system creates these
features by generating several patches. Our approach proposes a method to
create discontinuities on a single patch, using the trimming properties of the
surface. Examples are provided and analysed using curvature maps to address the
quality issue of the resulting shape as well as its capability to generate a
wide variety of shapes.