Control splines
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Summary
Control splines are used for facial setups where you want to simulate skin sliding by using a network of curves to simulate where the flow lines of deformation are on your character's face. Some areas are typically aligned with muscles, like the cheeks or forehead, while others align with boundaries, like eyelids and mouths.
Steps
The following is a suggested workflow for this deformation tool:
- Create a network of curves along contour lines of the face.
- You can either draw the curves with the snap tool active to snap the curve to the surface of the face, or you can draw the curve away from the face and use Deform > Shrinkwrap to place it on the surface (you will need to freeze the modeling operators of the curve if you use Shrinkwrap to position the curve).
- If a point from two curves overlaps exactly the control spline deformers will use a single control point. If you want this to happen, you can use Snap to ensure a point on differenct curves lines up correctly.
- Select the network of curves and Create > Skeleton > CreateControlSplines - in the dialogue box you can choose the type of controllers you want to use, how many control there are and how big the icons are.
- When you create these control splines, a group is created in your explorer view called 'envelope_group'. Select your face geometry and envelope this to the envelope group (Deform > Envelope > Set Envelope).
- Then select the Path control objects and set the up-vector object for their path constraints - eg to the head bone.
- Use the controls to deform the surface of the envelope, the amount of deformation effect will be controlled by normal envelope weight editing.
More Information
The resulting deformation network is reasonably complex, so a recommended workflow is to use a curve network of control splines in this way to generate shapes for the enveloped geometry. Then the spline control can be removed and the face geometry can be animated using shape animation which would involve less computation.
Applies To: XSI 4.0 on Win2K,Linux
Posted: 7/6/2004
