Design Realization lecture 8 John Canny 9/18/03

Preamble  Handouts include the Maya bible chapters on skeletons and IK.  First assignment models are due on the swiki today.  New Dell PCs arrived so there will be more machines running Maya unlimited.

Last Time  Kinematics – skeletons and joint hierarchies.  Local coordinate systems.  Inverse kinematics.

This time – kinematics & constraints  Lets start with the joint-creating tool:  (Animation) →Skeleton → Joint tool  Use default settings  Draw each joint (front view usually).  Adjust “joint” transforms so all moving axes are Z axes.  Recall that X displacement should give link length.

Binding skin  Actually very easy.  Select the skin to be bound, and the top link of the joint hierarchy to bind it to.  Then select Skin → Bind skin And choose either rigid or smooth bind.

IK and constraints  IK allows us to position a given joint.  To control other attributes, we use constraints.  E.g. we can create a handle which is used as a constraint for both position and orientation.

Handles  The goal is to use IK, constraints and attributes to create full control “handle” for the object.  example

Dynamics  Dynamics deals with physical properties of objects:  Mass, moments.  Stiffness and damping (restitution).  Friction (static and dynamic).  Movement is governed by:  Newton’s laws (free movement).  Coulomb’s laws (friction).  Restitution models (many).

Dynamics  Dynamics deals with physical properties of objects:  Mass, moments.  Stiffness and damping (restitution).  Friction (static and dynamic).  Movement is governed by:  Newton’s laws (free movement).  Coulomb’s laws (friction).  Restitution models (many).

Dynamics  Note: free bodies don’t simply spin. Newton’s laws imply a more complicated motion…  Rolling and sliding objects have strange behavior: movies.  Impulse = Fdt

Wrapup  Chair designs due on Swiki today.  Who still needs the 2 nd round of CD data?  Make sure you have a copy of assignment 2.