Animating facial expressions, particularly using blend shapes, can be difficult and time consuming. Early testing at this stage is imperative, to guarantee that you won't have to redo work at a later stage.
The best approach for testing the face is to try and create some of the more extreme facial expressions your lead artist has indicated will be needed for the character, and see how it holds up. These could include a shouting face with the mouth wide open, and maybe a face with the lips puckered up and eyes closed.
Begin by hiding everything that is not related to the face. Figure 6.38 shows what you should be left with: just the head and eyes.
Figure 6.38. Create a duplicate of the current head and eyes to work on.
Create a copy of these elements to work on, and hide the originals.
We work on copies so that we don't inadvertently edit the main head. We'd have problems if we couldn't undo an operation or get back to the base geometry.
Place the duplicate head and eyes into a group, calling it Angry, and begin working on this piece to create an angry, shouting look like the one in Figure 6.39. You can achieve this by simply moving vertices, but make sure you edit both sides of the face.
Figure 6.39. Create an angry, shouting face.
While editing the face, look out for any areas that don't deform correctly. In particular, look for polygons that appear concave when adjusted.
The main face looks okay, but the lips may cause a problem when animated. At the moment the upper and lower lips meet in the corners; the resulting pinch is unnatural and may cause some rendering artifacts (Figure 6.40, left). To prevent this, we want the lips to form a complete loop, as shown in Figure 6.40 on the right.
Focus in on the lips of the original head model (Figure 6.41a).
Figure 6.41. Alter the lips, removing the pinch that occurs in the corners when they animate.
As shown in Figure 6.41b, create a cut around the outside of the corners of the lips.
Weld all the new vertices together, creating the new outside edge of the lips (Figure 6.41c).
Select the edges leading into the old corner of the lips and use the Flip Triangle Edge tool (Edit Polygons > Flip Triangle Edge) to rotate them (Figures 6.41d and 6.41e).
Convert the polygons highlighted in Figure 6.41f into quads.
Adjust the lips, fixing the overall shape.
Figure 6.40. As is, the lips will not animate well.
In this state, the lips don't look much different, but when we open her mouth again (Figure 6.42) you will see the difference.
Figure 6.42. The new mouth
Let's test another facial expression.
Hide the Angry face group, and create another duplicate of the original. Call it Pucker and group it.
Test the eyes and lips by closing the eyes and puckering up the lips (Figure 6.43).
Figure 6.43. Sculpt the face to close the eyes and pucker the lips.
When I generated this face, I noticed a few minor areas that could use improvement:
The eyeballs were too far forward, so I had to move them back. This meant I had to edit the shape of the eyes slightly.
Looking from the side, the eyelids were almost flat. A real eyelid follows the curve of the eyeball, so I adjusted the vertices to correct the overall shape.
Now we implement all the alterations we did for our duplicates in our main model and we are done.
The face will now hold up to the mouth being opened wide and also tightly closed. The eyes will successfully open and close, too. Deformation testing is now complete.
Save your work as Kila_DeformTest.mb.