Modeling a face using Maya or any other 3D art program is tough to do without having the result end up looking like a zombie. See the film Final Fantasy: The Spirit Within if you don't know what I'm talking about. This six-part video will help you avoid this problem in your own 3D models by teaching you how to 3D model a face using the head extrusion method in Maya. You'll need a photo to start with (the creator does not supply the one he used here) but once you have that you should be able to follow along and improve your skills.
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