Wednesday, April 02, 2008

Eye Movements 3

Continuing his posts on animating eyes, Kevin writes:

Eye movements can be classified into seven different types:

Convergence is a motion of both eyes relative to each other that ensures that an object is still foveated by both eyes when its distance from the observer is changed. The closer the object is, the more the eyes point towards each other. This movement can be voluntarily controlled, but is normally the result of a moving stimulus.

Saccades are the principal method for moving the eyes to a different part of the visual scene, and are sudden, rapid movements of the eyes. Saccades can be initiated voluntarily, but are ballistic: that is, once they are initiated, their path of motion and destination cannot be changed. Visual input is suppressed during a saccade ...

Pursuit motion is a much smoother, slower movement than a saccade; it acts to keep a moving object foveated. It cannot be induced voluntarily, but requires a moving object in the visual field. One frequent failing of thoughtless animation is having the eyes demonstrate pursuit motion when there is no object being followed by the character’s eyes.

Nystagmus is a saw-toothed pattern of eye movements that occurs as a response to the turning of the head (acceleration detected by the inner ear) or the viewing of a moving, repetitive pattern (the train window phenomenon). It consists of smooth `pursuit’ motion in one direction to follow a position in the scene, followed by a fast motion in the opposite direction to select a new position. This is an eye movement that has probably never been animated, and if it was, it would probably get rejected by the supervisor or director because it would look so odd ...

Click on the link above for Kevin's complete post on lall seven types of eye movements ... and his take on animation of those little round orbs in the upper part of the face ...


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