During this tutorial you will be creating a low resolution ‘stand-in’ model of the reovirus sigma 1 protein (the tentacle-like trimeric protein that extends out of the virus’ turrets). The 3 monomers are thought to be in a flexible conformation during the early phases of the viral life cycle – once the surface of the virus loses its sigma3 coating (upon cleavage by chymotrypsin in the gut lumen), the sigma1 trimer transitions to a coiled-coil conformation and rigidifies. Therefore, we would like to animate each monomer as a flexible/trembling arm initially, and then have it erect and coil as a triple helix (with the other 2 rigid monomers).

Technically, in Maya, we can achieve this by creating a skeleton or joint-chain within the structure, and then bind (or ‘skin’) that skeleton to the geometry. We will then apply inverse kinematics to this skeleton in order to simplify its animation – we will ‘key’ the position of the inverse kinematic handle (IK handle) over time and then explore how to loop that motion cyclically in the graph editor. To achieve a ‘trembling’ motion on the sigma1 tentacles, there are several options to explore: 1) we will apply a simple expression to the x, y, z translate values of the IK handle, and 2) we will use values sampled from a fractal texture (yes, a texture!) to drive the movements of the IK handle. Finally, when the flailing monomers are ready to rigidify and twist around one another, we will apply a twist deformer to the trimer geometry.

Download pdf Maya 103: Animation