Game Development Reference
In-Depth Information
Two of the most popular methods today of real-time facial animation use either joints or
blend shapes
. Joint-based animation simply uses a series of joints placed around the face
that, when moved, serve to animate the character's face. Blend shapes, or
morph targets,
use duplicates of the face as a reference. The main face then morphs into the vertex-modi-
fied reference shapes.
This chapter demonstrates how to set up your characters using joints and using blend
shapes,sothatyoucanmakeupyourownmindaboutwhichonetouseinaparticularsitu-
ation.
Your choice will depend heavily on the game engine, so consult with the lead programmer
first before embarking on a particular method. In addition, discuss the matter with your
manager before you start work. Find out exactly what the character will need to do. If all it
will ever do is blink, then there is no need to spend time creating multiple face shapes.
Joint-Based Facial Animation Setup (Kila)
Themostobviouswaytoanimateacharacter'sfaceistousejoints,becausewearealready
employing them to animate the body. We simply place joints at certain places around the
character's face, which will then act like muscles, moving the vertices around and animat-
ing the face.
Where do we put facial joints to get the best facial expressions on Kila?
We need one to operate the mouth, opening and closing the jaw.
For the eyes, we'll add joints that operate the eyelids.
Joints at several locations around the mouth will give movement to the lips, en-
abling the character to form words.
The eyebrows contribute a lot to facial expression, so we can add joints to move
these as well.
If our budget allows, we can add the ability to animate the tongue.
Two more joints will add movement to the cheeks.
This list includes quite a few extra joints, so for your own project, make sure you have
room in your budget. In this chapter, we will implement them all.
Joint Placement
As we did with Kila's breasts, we will rely mostly on the translations of joints to animate
the face. We only need to add joints to the left side of her face, and then mirror these to
create the right side.
