IMD 4003: Rigid Bodies II

For IMD 4003: Computer Animation, taught by Chris Joslin

Contents

1. 1. Point and Objects
2. 2. Translation and Rotation
3. 3. Inverse Kinematics

1. Point and Objects

objects are composed of points (vertices) and connected by lines (edges). If you connect vertices with edges in a somewhat organized way, you can create recognizable objects in the World Coordinate System.

2. Translation and Rotation

The value of the vertices (x, y, z) doesn't matter as long as the vertices relate to each correctly. That is, the distance between the vertices is what matters.

Example: Pretend you have a vertex at (0,0,0) and another at (1,0,0). They are connected by an edge. If you move them by 1 positive unit on the x-axis, you get (1,0,0) and (2,0,0). The distance between the 2 vertices are the same - they aren't deformed when you translate them.

For this reason, the translation of an object is easy.

Rotation: if we use xform or setAttr, we are moving the local coordinate system - we are rotating the objects pivot point.

Pivot Points: the point around which the object will rotate.

3. Inverse Kinematics

Because I found inverse kinematics boring and hard to absorb, I never finished these notes (sorry!).