Dynamic Wrinkle Simulation for 3D Facial Expressions
Wrinkles are the main factor determining the undulation of the skin surface. Since skin material itself is incompressible, when the skin surface shrinks, the excess skin buckles and forms wrinkles. Facial wrinkles can be classified into two types: expressive wrinkles and wrinkles due to age Expressive wrinkles are temporary wrinkles that appear on the face during expressions at all ages. These wrinkles are caused by the contraction of underlying muscles and are perpendicular to their axis of shortening. The height of the wrinkle bulge depends on the degree of muscle contraction (see Figure 1). The skin cells regenerate themselves at slow rate with age, and tend to favor a specific orientation, thus creating aging wrinkles. In this project, we are only concerned with the expressive wrinkles.
Figure 1: Temporary wrinkles on the face during expressions.
As expressive wrinkles are formed due to compression of the skin surface as a result of muscle contraction, we believe that wrinkle simulation can be greatly facilitated if anatomical face structure is used. Therefore, our goal is to realistically and fast simulate wrinkles according to the influence of virtual facial muscles. We propose a geometric muscle-driven wrinkle model to efficiently simulate realistic expressive wrinkles on the face. Wrinkles are generated on an anatomy-based face model that mimics the layered skin-muscle-skull structure and dynamics of the human face. Corresponding to three types of facial muscles, a geometric model is developed to govern how the wrinkle amplitude evolves locally upon skin deformation. By taking into account the properties of real wrinkles, it provides intuitive parameters for easy control over wrinkle characteristics. During facial animation, wrinkles are generated in the local regions influenced by muscle contraction, simulating resistance to compression of tissues. Our facial animation system automatically adapts the local resolution at which the inadequacy of mesh approximation is detected depending on a refinement criterion, where different levels of resolution are provided in order to reduce the overall complexity by only simulating relevant levels of detail. Thanks to its simplicity and geometric nature, our method simulates wrinkles that can be dynamically rendered at interactive rates.
The original contribution of our method is given in terms of the following advantages:
As expressive wrinkles are formed due to compression of the skin as a result of muscle contraction, our
method is to automatically determine their locations and directions according to influence of facial muscles.
The proposed wrinkle model takes
into account the properties of real wrinkles and provides
intuitive parameters (e.g., width, height and depth) to easily
control wrinkle characteristics.
Our geometric muscle-driven method is efficient in time complexity, simple to implement, and performs fast.
The automatic adaptive refinement that couples multiresolution and deformation maximizes the overall realism while ensuring frame rate.
Simulation of dynamic wrinkles on a skin patch under contraction of the linear muscle, sheet muscle and sphincter muscle.
Muscle structure of the face model.
Simulated facial expressions with wrinkles. They are compared to expression animation without wrinkles and actual expressions.
Simulated facial expressions: (a) neutral face, (b) surprise, (c) frowning, (d) closing
eye, (e) stretching mouth, and (f) fear. Top to bottom: expression without wrinkles, expression
with wrinkles, actual expression generated by a subject (each example).
Dynamic simulation of expressive wrinkles with mesh adaptive refinement.
Papers:
Yu Zhang and Terence Sim. "Realistic and efficient wrinkle simulation using an anatomy-based face model with adaptive refinement". Proc. Computer Graphics International 2005 (CGI2005), IEEE Computer Society Press, to appear, Stony Brook, New York, USA, June 2005.
Yu Zhang, Terence Sim and Chew Lim Tan. "Simulating wrinkles in facial expressions on an anatomy-based face". Proc. 4th International Workshop on Computer Graphics and Geometric Modeling (CGGM2005), Springer-Verlag, ISBN: 3-540-26043-9, pp. 207-214, Atlanta, USA, May 2005.
Copyright 2005 to 2013, Yu
Zhang. This material may not be published, modified or otherwise
redistributed in whole or part without prior approval.
