Don Slaterdslater@andrew.cmu.edu

Wanda Dannwpdann@andrew.cmu.edu

Joint Operations

Copyright 2012 Wanda Dann, Don SlaterAll rights reserved

Objects often (not always) have internal joints that can be animated to control subparts of the model.

A joint connects a subpart of the body to the rest of the body

A joint can be turned or rolled but cannot be moved

Internal Joints

Biped X-ray

Quadruped X-ray

A subpart may be connected to another subpartRotating one subpart may also rotate other subpartsExamples:

Turning the left shoulder joint will turn the entire arm of the alien, including the forearm, wrist, hand, fingers, etc.

Turning the left elbow joint will turn the alien’s forearm, wrist, hand, fingers, etc.

Subpart LocationConnected subparts

To access a joint, click on the arrow next to the object’s name in the instance list.

In the Code Editor

In the Scene Editor

By clicking on Show Joints and adjusting the opacity in the Scene Editor, you are able to see the joints of any model.

• Add axes object to the scene

• Move and orient the axes to the joint

• The white axis points forward, red to the right, green up

Orientation of a joint

Orientation: whole vs. part

The orientation of a subpart is not necessarily the same as the orientation of the whole object.

A subpart cannot be moved

A move would detach the joint (and its connected subpart) from rest of the model, so a move action is NOT allowed for a subpart of an object.

Translational Motion: Joints

A subpart’s joint acts as its pivot point for rotation of the subpart.

Two forms of rotational motion: turn

forward, backward left, right

roll left, right

Rotational Motion: Joint/Subpart

Rotation of a joint

Turn forward/backward

Red Handle: Turns joint forward and backward

Turn left/right

Green Handle: Turns joint left and right

Roll left/right

Blue Handle: Rolls joint left and right