Organic Modeling and Animation - Part One (Modelin

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Sep 03, 2005

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Figure Thirteen

Sculpt deformers allow for the interactive massing of form via spherical objects which can be moved, rotated and scaled. These deformers can be placed on selected vertices, individual surfaces, or onto multiple surfaces. There are three types of Sculpts--- Stretch, Project and Flip--- all of which have animatable controls for dropoff and magnitude. Stretch, the default, deforms the surface based on the relative position of the Sculpt object and a 'Locator' object, whose purpose is to define the origin of the deformation. Flip mode, which I use most often, causes the geometry to be attracted or repelled by the the Sculpt object based on the shape, rotation or position of the deformer. Figure 13 shows several variations of Lanker's head created in under ten minutes using Flip mode Sculpt deformers. The main problem I've run into is hard edges at the edge of the Sculpt deformation, but this is very quickly remedied using Artisan's Smooth mode as described eariler. The tightly packed isoparms creating the hard edge can be spread apart smoothly using a pressure sensative drawing tablet.


Figure Fourteen


Figure Fifteen

Lattice deformations, like Sculpts, can be added to either components or objects. If placed on multiple surfaces, shared edges will maintain their appropriate relationships as long as the entire seam is a member to the deformer. The main benefit of Lattices is the ease with which we can change the overall shape of a dense area by manipulating only a few Lattice Points. Furthermore, Maya allows us to place deformers upon deformers, meaning that we can add a Sculpt to a Lattice which itself was added to a Lattice whose edit points may be members of a Cluster. Figure 14 shows an example of using a combination of Lattices to completely change the head. First a Lattice was added to the mouth region to reshape it. Then a Lattice was added to the entire surface to tweak its overall shape some more. Finally, another, less subdivided, Lattice was added to the larger Lattice to reshape things again. Figure 15 shows the result of placing Lattices and Sculpts onto multiple surfaces, giving Lanker a few extra pounds without breaking our seams. Again, edges will not separate as long as the deformer was added to both surfaces which share the edge.


Figure Sixteen

Wire deformers allow us to sculpt surfaces using curves as the source of deformation. These curves offer complete control over strength, enveloping, dropoff, and crossover effects, which occur when wires cross. Furthermore, multiple Wire Dropoff Locators can be positioned any where along the curve to create varying effects. Wrinkle deformers offer some preset controls for creating large numbers of wires which can be created tangentially or radially, branching out from a region of the deforming surface. The most useful technique for creating curves to use as wires or wrinkles is to select the desired surface and make it 'Live' using Modify/MakeLive, allowing us to draw a curve directly onto the surface. This 'Curve on Surface' should then be duplicated using Curves/Duplicate Curve to create a free, standalone curve. Curves on Surface as wires are of little use, as you will not be able to deform the surface in any direction other than U or V; but our duplicated curve will work fine. You may want to move it a small amount away from the surface before turning it into a Wire, just to make it easier to see. Figure 16 shows a combination of Wires, Wrinkles, Clusters and Dropoff Locators.

Conclusion


Figure Seventeen

The combination of Maya's deformation tools illustrated in this tutorial allows for a quick and intuitive modeling process. Figure 17 shows all the targets which I sculpted for the head, focusing on major muscle groups, such as the currogator, frontalis, triangularis, and so on. Using BlendShape, we will be able to merge these targets to create slider driven expressions, such as happy and sad, and phomenes such as 'oo' and 'ah'.

Part two of this article will focus on skeletons, forward/inverse kinematics, expressions, and custom object attributes. The series will conclude in part three with skeleton-driven surface deformations and animation techniques including advanced constraint keyframing, facial animation and sound synchronization.



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