RESEARCH.
ALIAS WAVEFRONT'S - MAYA 1.0.
Maya 1.0 primarily uses keyframe based morphing techniques. Like
'Realistic
Human Faces' it can use a global blending method or a local regional
blending method. Maya uses what it calls Blendshapes to generate
the morph targets. These are essentially copies of the base geometry
which form morph targets. Maya achieves local morphing by storing
the control points of the base geometry, and displacing them to the new
positions of the target geometry. This is very efficient in terms
of physical memory as the newly created target shapes can be deleted and
just the points stored, thus speeding up screen update.
These morph shapes are then placed inside a user interface consisting of
rows of slider bars, for easy interaction. (see
Fig 3.)
Fig . 3. Blend Shape User Interface.
It is important to note that standard morphing
isn't the only option for facial animation within Maya. The actual weighting
of the morph targets can be scaled to produce deformations beyond the target
shapes. Maya also implements a 'world' and 'local' morphing.
World morphing means that the base shape moves to the target's position,
scale and rotation. Local means that the base shape only takes on
the appearance of the target. Target's can be 'chained' together
so that manipulating one slider deforms the base through a sequence of
targets. Shapes that possess different topologies can also
be morphed. Most animation systems specify that the target shapes
possess the same number of cv's or vertices as the base.
Maya also implements a range of deformation tools which can not only be
used for modelling, but also for animating. The 'Wire' tool is one
such option. The wire deformer allows geometry to be deformed based
on free-form curves. The surfaces are deformed simply by manipulating
the points on the curve. (see Fig 4.)
Base wires, a wire deformer's secondary influence,
are duplicate curves that Maya creates when you assign the curve to be
a wire deformer.
The base wire acts as an anchor to the wires: the deformation occurs on
the geometry in a straight line from the base wire to the wire deformer.
Maya allows the user to create curves called 'holders'. Holder curves
allow deformation of the object up to the point of the holder, regardless
of the drop-off applied to the wire. The significance of this
in terms of eyebrows are tremendous.
Standard deformation lattices can also be applied to the object and used
for animation. In fact any deformation tool within Maya can be used
for animation. In this report I have only listed the relevant deformers
for facial animation. In theory any
of the other deformation tools could be used for facial animation.
I have focused on those which I feel were originally intended for the creation
of facial expressions.
Fig . 4. Wire Deformer.