The purpose of using 3D avatars, or animation itself is the ability to do things that you can’t do in real life. In our simulation we will need to be able to change the avatar’s appearance in many ways. Among some of these transformations we are looking into ways of aging the avatar, and controlling their body weight to make them more obese or healthy depending on the situation they are presented with in the simulation.
Below is a an animated picture of one method of achieving this effect. Many graphics applications have morph features that allow an object to change, from one shape to another, as long as it has the same geometry (the points and faces are the same).
Although the method described above is ideal, as it allows the artist to shape or sculpt the model as needed, such an effect has been achieved in the past (in games and realtime applications) through the use of bone animation.
Below is another picture that shows how this same effect can be achieved with this method. The bones influencing the shape are highlighted in red.
We can also use bump and normal maps to help obtain this aging effect. These could be used to create wrinkles on the character without having build them into the actual model.
A bump map is basically a black and white image that tells the computer to interpret the darker areas as depressions on a surface, and the lighter parts as elevations.
A normal map is similar to the bump map, but it uses 3 colors to give a more 3 dimensional feel of what the object looks like, and how light reacts to its surface.
The following images are some examples of each. The first image shows a bump map implemented on some environment objects in the Unity 3D engine. The second image illustrates a normal map applied on a 3D object.