1. Design Realization lecture 7 John Canny 9/15/03

2. Preamble  Blog for Maya is up now, but you need to be added as an author. Mail one of the current authors.  We will finish project review today.

3. Last Time  Materials and textures.  Displacement and bump mapping.  Texture coordinates.  Qualities of movement.  Keyframing  Specify sample poses and transitions.  Edit trajectories like curves.  Elements of a movement.  Anticipation, Action, Recovery.

4. Kinematics  Kinematics (from kinema/cinema to move).  Kinematics typically involves chains of joints, to represent movement of living things.  Transformations are applied from the beginning to the end of a kinematic chain:  E.g. from shoulder to fingers

5. Kinematics  If p is a point and T is a transformation matrix, then Tp is the new position of p.  If joints are numbered from 1,…,n, then the position of a point on the last link is: T 1 T 2 (T 3 … (T n p))  In other words, the finger is moved by the shoulder, elbow and wrist joints.

6. Local joint coordinates  Because transformation matrices change coordinates of points, the position of joint axes is not unique.  The standard method is to use a local coordinate system for each link.  Z axis is aligned along the joint.  X axis is aligned normal to both joints.  Therefore X displacement measures link length.

7. Local joint coordinates  Maya places the local coordinate transforms information in a “joint” attribute.  You always see the joint transform as a zero rotation, with an X displacement to the next joint (the link length).

8. Inverse Kinematics  Whenever we reach for something or take a step, we have to solve for many joint angles – this is inverse kinematics.  Maya provides several kinds of solver that allow you to control hands, feet etc. directly.  They create virtual objects (handles) that can be moved and keyed in the usual way.

9. Todo  Chair designs due on Swiki by Thursday.  Make sure you get added to the blog editors list.  Extra material: shaders and MayaBible  Just copy onto your disk