How to make virtual figures look real in an animation remains a challenging problem in computer graphics. Researchers have converged their exploration routes to employing biomechanical modeling techniques to simulate different parts of the body. Such physics-based simulation techniques give researchers hope that the virtual figures will act realistically at a very detailed level.

Before the research conducted by the authors of this paper, many other researchers had modeled human body parts biomechanically--in a discrete fashion. The advance made by Lee, Sifakis, and Terzopoulos is that they undertook a detailed biomechanical modeling of the entire upper human body, including most of the articular bones and muscles. Their research confronts the combined challenge of modeling and controlling a large number of parts at the same time, modeling their interactions, modeling the realistic deformations of muscles, and the performance issues in such a large-scale simulation. They detail their approach to solve this challenge. Their numerical experiments are pretty thorough and the results are promising.

There are some limitations in the paper. First, the muscles’ material model is greatly simplified to save computational load; it would have been better if there had been a discussion about the effects of material models on muscle deformation. Second, it is not clear how the authors take into account the contact between muscles. Such contact can affect muscle deformation, sometimes to a great extent.