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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.

 
 

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