13. One or more non-transitory computer-readable storage medium comprising a plurality of instructions to cause a computing device, in response to execution of the instructions by the computing device, to cause the computing device to: detect and track a user gesture that corresponds to a canned facial expression, the user gesture including a duration component corresponding to a duration the canned facial expression is to be animated, and in response to a detection and tracking of the user gesture, output one or more animation messages that describe the detection or the tracking of the user gesture or identify the canned facial expression, and the duration; and drive an avatar model, in accordance with the one or more animation messages, to animate the avatar with animation of the canned facial expressions for the duration; wherein to animate the canned facial expression comprise to blend one or more pre-defined shapes into a neutral face during a start period, to hold the avatar at the canned facial expression for the duration during a keep period, and to terminate animation of the canned facial expression by un-blending the one or more pre-defined shapes to return the avatar to the neutral face during an end period.
13. One or more non-transitory computer-readable storage medium comprising a plurality of instructions to cause a computing device, in response to execution of the instructions by the computing device, to cause the computing device to: detect and track a user gesture that corresponds to a canned facial expression, the user gesture including a duration component corresponding to a duration the canned facial expression is to be animated, and in response to a detection and tracking of the user gesture, output one or more animation messages that describe the detection or the tracking of the user gesture or identify the canned facial expression, and the duration; and drive an avatar model, in accordance with the one or more animation messages, to animate the avatar with animation of the canned facial expressions for the duration; wherein to animate the canned facial expression comprise to blend one or more pre-defined shapes into a neutral face during a start period, to hold the avatar at the canned facial expression for the duration during a keep period, and to terminate animation of the canned facial expression by un-blending the one or more pre-defined shapes to return the avatar to the neutral face during an end period. 17. The computer-readable storage medium of claim 13 , wherein the computing device is further caused to accept definition of the user gesture, including finger movement trajectory, hand gestures, or facial gestures in defining the user gesture.