Description
Characters can change the expressions in their faces by activating one or more Facial Action Units, abbreviated as Action Units (AU). Each AU activates a different part of the face, say, raising an eyebrow or widening the nose. The AUs can be combined together to form more complex facial expressions
Note that the facial movements expressed by the <face> BML command are separate from lip synching, which manages the mouth and tongue shapes in order to match speech. There are AUs that can operate on the tongue, mouth and lips, but they would be activated separately from the lip sync activation. For example, if you wanted your character to open his mouth and raise his eyebrows to express surprise, the open mouth expression should be activated by triggering AU 26 which lowers the jaw. While a similar expression could be accomplished by using a viseme which would lower the jaw, visemes are typically only activated in response to speech, while AUs are activated via BML commands.
Requirements
Characters need to have a Face Definition set up with any number of AUs.Please see the section on Configuring Characters for more detail. Note that both joint-driven faces and blendshape-driven faces are supported. In the case of joint-driven faces, an static pose will correspond to each AU. In the case of blendshape-driven faces, SmartBody will transmit an activation value for that shape, and it is the task of the renderer to interpret that activation value and activate the appropriate shape.
Usage
<face type="facs" au="1" amount="1"/>
Complex facial movements will contain numerous <face> commands using different attributes. For example, a happy expression could be AU 6 and AU 12:
<face type="facs" au="6" amount="1"/><face type="facs" au="12" amount="1"/>
or sadness could be AU 1 and AU 4 and AU 15:
<face type="facs" au="1" amount="1"/><face type="facs" au="4" amount="1"/><face type="facs" au="15" amount="1"/>
Parameters
| Parameter | Description | Example |
|---|---|---|
| type | Type of facial expression. Only 'facs' is currently supported. | <face type="facs" au="1" amount="1"/> |
| side | Which side of the face will be activated; LEFT, RIGHT or BOTH | <face type="facs" au="1" side="LEFT" amount="1"/> |
| au | Action Unit number | <face type="facs" au="26" amount="1"/> |
| start | when the face movements starts | <face type="facs" au="26" amount="1" start="2"/> |
| ready | when the face movement is fully blended in, default is .25 seconds | <face type="facs" au="26" amount="1" start="0" ready="1"/> |
| stroke | the mid-point of the face movement | <face type="facs" au="26" amount="1" stroke="4"/> |
| relax | when the face movement starts blending out, default is .25 seconds | <face type="facs" au="26" amount="1" relax="2"/> |
| end | when the face movement ends | <face type="facs" au="26" amount="1" start="0" end="4"/> |