Our main emphasis in making "Catz: Your Computer Petz" was to create five distinct, interactive and autonomous cat characters that express life-like personality. This illusion of life was achieved by concentrating our efforts on only what the user would perceive. We worked backwards from what we had the ability to show, and therefore did not waste time implementing an elaborate brain that couldn’t express itself. The different Cat personalities include prowling hunter Catz, lazy Catz, finicky Catz, playful Catz and scaredy Catz.

We developed many different animation methods of achieving this goal, most of which can animate simultaneously in real-time. We found that many simple animation and sound layers operating independently will combine to create a complex life-like product. Some of these layers include facial expression, general body movement, posture, head tracking, and vocal expression. A network of 3D real-time animation causes the user to never see exactly the same animation twice.

The use of constrained randomness creates unpredictable behavior, which is critical to create the illusion of life. Many repeating animations (e.g., walking or breathing) in Catz have alternate loops which are shuffled randomly to avoid the perception of repetition. Also randomness is peppered throughout the Cat’s high level decision making process.

Beyond life-like autonomy we focused on making the user’s interaction with the Cat as direct as possible. The mouse controls an animating hand-shaped cursor that allows users to stroke the Cat. The Cat immediately reacts in a variety of ways depending on what spot on its body is being petted, how fast, and how the Cat feels at the time. Also the user can pick the Cat up by the scruff of the neck and drag it around the desktop.

The toys and objects in the Cat’s environment (yarnball, food bowl, etc.) also have direct object-like interaction for both the user and the Cat. All this direct interaction allow users to feel they are touching something alive. We tried to allow the Cat to have as much access to toys as the user; for example, if hungry and unfed the Cat can scratch the food bowl out of the supply shelf itself.

In addition we created a Mouse character which lives in a mouse hole on the desktop. This simple character is a first experiment with the complex problem multiple character interaction. The user can lure the Mouse out of its hole with the cheese, but must the Mouse must beware of the Cat. The user can participate in the Cat-Mouse relationship in several ways, such as holding the Mouse for the Cat to capture, holding the Cat so the Mouse can run freely, moving the mouse hole so the Mouse can’t hide, and so on.

Catz: Your Computer Petz is available for PC and Macintosh CD-ROM.