Figure 2. Screenshot of teddy and sample 3D models created using
Figure 3. modeling session in teddy. the user can create a 3D model
using simple sketching operations.
the silhouette of the base primitive, and the system generates the corresponding 3D geometry. The user then draws
a stroke across the model and the system cuts the model at
the line. The user can also add parts to the base model by
drawing two strokes. Figure 2 right shows several 3D models
created using the system.
Several sketching systems for free-form shapes were developed after Teddy. The original Teddy system used polygonal
meshes, but some later systems experimented with other
representations such as voxels20 and implicit surfaces.
Some systems extended the interface to support subsequent
editing by direct manipulation. ShapeShop21 represents
a model as a collection of blob primitives and allows the
user to move or scale each primitive. Fibermesh19 keeps the
original stroke as a control curve on the model surface and
allows the user to adjust the shape by deforming the curves.
However, all these systems are designed for purely virtual 3D
models without consideration of the physical properties of
materials. Plushie is innovative in that it shows the feasibility of using a sketching interface for free-form shapes in the
design of physical objects.
3. DESiGninG Ph YSiCaL moDELS With
Another key aspect of our work is the tight integration of
physical simulation into the 3D modeling process. In traditional applications, modeling and simulation are completely separate. A virtual model is created in 3D modeling
software without considering any physical constraints,
and it is then passed to a simulation environment. If the
simulation result reveals a problem, the user returns to
the model to fix the problem. We made this process more
efficient by running the simulation concurrently with the
82 CommuniCationS oF thE aCm | DeCeMBeR 2009 | vOL. 52 | NO. 12
modeling to create only models that are physically realizable. In this way, the user can more efficiently explore the
design dimensions within realistic constraints. From the
user’s point of view, the model generated by the system
may not correspond exactly to the shape that was input,
but it will be a physically realizable shape reflecting the
Some recent systems have tried to incorporate fast physical simulation into an interactive design process. Igarashi
and Hughes developed a mark-based interface for putting
clothing on a virtual character,
10 and Decaudin et al. proposed a system for designing an original garment via sketching.
6 Both used simple geometric simulations to represent
the physical properties of cloth material. Masry and Lipson
described a system in which the user can quickly build a CAD
model by sketching and immediately apply a finite element
analysis to the model.
15 However, the model construction is
computed before the simulation in these systems, and no
dynamic feedback loop exists between the simulation result
and the original user input.
Several efforts have also been made to support the design
of physical objects by end users in the computer graphics
research community. Mitani and Suzuki16 and Shatz et al.
presented automatic segmentation of a 3D model into surface patches that can be perfectly flattened onto a plane
without distortion for constructing paper craft models.
Similarly, Julius et al. proposed similar method for plush
toys14 allowing small distortion. Pillow system17 facilitates
the manual segmentation of a model by providing automatic
flattening and by showing the result of physical simulation.
These systems make plush-toy design more accessible, but
the fundamental challenge of creating an original plush toy
is still unresolved.
4. thE PLuShiE SYStEm
The system consists of two windows: one shows the 3D
plush-toy model being constructed and the other shows
the corresponding 2D pattern (Figure 4). The user works on
the 3D view, interactively building the 3D model by using a
sketching interface. The 2D view is mainly for reference but
the user can also edit the 2D pattern directly when desired.
The 3D model is produced from a physical simulation of
the assembled 2D pattern. After each input from the user,
Figure 4. a screen snapshot of the Plushie system.