Controlling Both Sides of the Face with Blend Shapes and Controllers

by Brian Immel

This tutorial extends the process and knowledge of SDK Blend shapes and talks about setting up head models, control objects, and blend shapes for animating both the left and right side of the face for the purpose of facial animation.

 

1. Create the models for each position of the brow (four heads: up and in on both right and left sides).

2. Name each head according to its function: brow_L_up, brow_L_in, brow_R_up, brow_R_in.

3. Select both the left brow heads and the bridge head last. Go to Deform > Create Blend Shape > Option Box. Type in Brow_Left for the name of the blend shape. Go to the Advance tab, and select Parallel for the Deformation Order. This step is very important. Otherwise, your sets of blend shapes will not work. If left to Default, Maya will only calculate one blend shape node at a time once another blend shape node has reached it's limit.

4. Select both the right brow heads and the bridge head last. Go to Deform > Create Blend Shape > Option Box. Type in Brow_Right for the name of the blend shape. Go to the Advance tab, and select Parallel for the Deformation Order.

5. Create a locator and name it brow_control.

6. Create the text Brow and scale it so that if fits nicely above the locator controls. Ungroup all the curves created within this grouping.

7. Parent these curves to the locator and then lock all the attributes so that they cannot be manipulated in the future.

8. Freeze transformations and lock the location (limits of Tx 1 and –1 and Ty of 1 and –1) just like we did in the One Control, Four SDKed Blend Shapes tutorial. Lock out all the attributes that we will not be using for this control object.

9. Use the Set Driven Key window just like we did with the four basic visimes to control the brows.
Select both the blendshape nodes and load them as the Driven in the SDK window. It may be difficult to select both blend shape nodes so use the Hypergraph. Select the bridge head and hit the f key (focus selected) to see the selected node in the Hypergraph window. Hit the Input and Output Connections button to see all the nodes connected the the bridge head. The illustration to the right shows what this may look like and which nodes to select. Note the highlighted nodes and the icons (these are blend shape nodes).

10. Set up the SDKs of the brow controller (driver) to the blend shapes of the brows (driven) just like we did for the mouth visimes control.
TranslateY will handle the brows going up (TranslateY=1) and the brows going in (TranslateY=-1).

• Basic premise:
  If Ty = 1 then Brow_Up left and right blendshapes = 1.
  If Ty = -1 then Brow_In left and right blendshapes = 1.
• Note: If you did not set up your blend shape nodes to with the deformation order of Parallel, you will notice what looks like an error or problem with the blend shape ‘canceling’ one another out or not blending fully. You will need to delete history off the bridge head and rebuild the blend shape connections with the proper deformation order.

11. To control which side is active (left, right or both), we need to set up TranslateX to turn the left and right sides on and off. To do this we need to tell TranslateX to handle the envelopes of each blendshape (Brow_Left and Brow_Right).

• Basic premise:
  If Tx = 1 then the envelope to all left heads = 0.
  If Tx = -1 then the envelope to all right heads = 0.

• This illustration shows the end result with all the controls working to their extremes.

12. Now that we’ve set up the brows, we can apply this process to the happy/sad mouths, nose sneer, eye blinks and emotional eyes (if any). Refer to illustrations below for the values, settings and grid layout to the rest of the head set ups.

Enjoy!