Icon - Department of Computer Science - University of Victoria

Figure 3.2: An implicit model before (a) and after (b) spatial deformation is applied.
The green sphere represents a deformation field and the part inside the green sphere
is bent.
Modeling (PCM) [19] was proposed to simulate deformations of implicit objects under
collisions. Collisions are basically simulated by splitting the process into 2 steps:
collision detection and collision response. PCM introduced a new step called contact
modeling between those two steps. During the contact modeling step, the scalar fields
of implicit objects are deformed and the contact surface between them is generated.
C 1 continuity can be preserved even after collisions. This idea was extended into
[37, 10] which discussed local deformations, volume preservation, and blending control
for PCM. Schmitt et al. [49] proposed a deformation method for F-rep models [40, 39].
A more flexible deformation is possible than the methods described above by defining
another F-rep object as a deformation field. This principle is applied not only to
geometry but also attributes. For example, texture, one of the attributes, can also
be deformed by following geometric deformation.
The above methods work well for implicit models, but none of them are FFD
methods because they are not satisfied with the two important FFD properties (Sec-
tion 3.1). In this research, a more controllable and user friendly deformation technique
is investigated to achieve FFD for implicit surfaces using a sketch-based approach.
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