Computer Aided Ferret Design
My thesis topic was in tailoring Surface Pasting
to create ferrets. Ferrets are small bundles of personality from
the mustelid family. They have long narrow bodies that can assume
almost any curved shape, so splines are the natural tool for modelling
Previous techniques in surface pasting have the following problems that
makes it hard to model ferrets:
- pasting patches limits features to rectangular bumps, inadequate
for modelling arms, legs, eyes or ears
- the underlying rectangular structure of the feature is often visible
- the feature warps to the curvature of the base surface, not always
in a predictable way
modelled with patch pasting
Based on these observations, I improve modelling with
surface pasting in three ways.
1. Projective cylindrical pasting
I created a projective interface for pasting generalized cylinders.
The boundary points at the end of a cylinder are projected in the
direction of the cylinder's spine to achieve approximate C0
and C1 pastes.
pasting; approximate C0 and C1 pastes
This improvement allows me to build and paste arms and legs modelled
with generalized cylinders. In addition, cylinders with concave cross
sections can be pasted as well. And by trimming the outside of the
base surface rather than the inside, we have an effective method of
capping cylinders with concave cross sections.
C0 and C1 capping of a cylinder
with a ferret shaped cross section
2. Centroid projective patch pasting
I replaced the normal displacement patches with centroid
displacement patches. Control points are displaced from a centroid
which is used for pasting onto the base. All boundary points are
projected according to the coordinate frame of the centroid, which
also allows a somewhat unintuitive method of creating arbitrarily
shaped boundaries. Because inner control points are displaced from
the same location, the feature shape does not warp as much compared
to standard pasting.
standard pasting (centre), centroid projective pasting (right)
3. Trimmed patch pasting
I created the pasting of trimmed features. Patches are trimmed
and a cylinder created to blend the feature onto the base. This
allows easy creation of features with non rectangular boundaries
such as eyes and ears.
The final ferret is created with cylindrical body and limbs, trimmed
eyes and ears, and the limbs are capped for an approximate manifold.
from the side
to the patch pasted model, the new model is much better!
there is plenty of room for improvement before we approximate the
And if we can model ferrets, we can model plenty of other things!
Here are some things to read
Here are some talks to look at