Facial Modeling and Animation

Hierarchical B-splines are an advanced free-form modelling and animation system for 3D character animation and related applications. "Dragon" is the name of an interactive modelling system based upon Hierarchical B-splines, written for the Silicon Graphics workstation platform. Based on a radical reconception of smooth-skinned surfaces and their movement, Dragon provides intuitive sculptural control over complex shapes both during design and subsequent animation.

Due to the unique hierarchical organization of both surface and motion data, generic templates can be used to accelerate the development of custom characters and animations without sacrificing individuality and functionality. Unlike polygonal models scanned from real world data, Dragon's surfaces remain completely flexible and editable, resulting in an expressive range traditionally un-achievable with a single continuous model. Moreover, libraries for both joint motion and skin deformation can be transferred between characters with similar morphology and blended with local actions and expressions.

The model was created in SoftImage, (Thanks to Chris Welmann and Ian Pearson for lending us an early prototype for the character "Mouse" in the YTV television series "ReBoot"). The original standard bicubic B-spline was imported to the "Dragon" editor and a hierarchy automatically constructed. The surface was attached to a jaw to allow it to open and close the mouth. Groups of control vertices were then moved around to created various facial expressions.

None of the expressions below took more than 20 minutes to build, the shortest took about five minutes (we timed it). Three of these expressions were chosen as key shapes, the spline surface was exported back to SoftImage, and the key shapes were interpolated to create the final animation taking another 15 minutes.

Here are some more expressions:

And some more...

Muscle Models

Carol Wang's MSc thesis involved adding a facial animation system to the basic hierarchical B-spline editor. (Carol did her MSc degree at the University of Calgary co-supervised by Brian Wyvill and David Winter. She is now working for Side Effects Software Inc. (Toronto).). The system is based upon Ekman's Facial Action Coding System (FACS) and involves simulating the effect of various muscle groups upon the shape of the face. About 46 different muscles (23 each for each side of the face) are used.



27) the basic model for the head. This surface was orginally created by Carol and subsequently modified by Goesta Struve-Dencher and David Forsey .

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28-32) This is a miscellaneous collection of heads derived from the base. The whole collection was built in a couple of hours.

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33-36) This is a collection of facial expressions intending to show sadness, fear, disgust and a smirk.

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37-38) Facial expressions for the dragon head created by moving the underlying skeleton. The smile was added by moving one control vertex.

The following figures show the use of a procedural offset method and a Behavior Map to create surface folds and creases on an otherwise smooth hierarchical B-spline surface.

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39-40) Folds on a plane, and creases on a human forehead.

Body Modelling and Animation:

Example Facial Animations:

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Last updated by David Forsey on 1 Feb. 95.