[Japanese | Thesis | Researches in Minoh Lab | Minoh Lab]

Elastic Deformation of Human Body Model Using Finite Element Method

As a result of rapid progress of computer technology, the computer-synthesi-\\ze d animations using three-dimensional human shape models are used in television ,movies,games and so on. In these fields,there are strong demands to make comput e-synthesized animations of human motions more realistic. The previous methods to synthesize animations of human motions have used human b ody models with rigid parts. But, a human body consists of soft parts. Arms and legs change their shapes as muscles stretch, and the abdomen and the buttocks ch ange their shapes as the fat is deformed by the power of inertia. Therefore, the previous methods cannot synthesize realistic animation of human motions.

In order to obtain computer-synthesized animations of human motions ,an elastic deformation method for three-dimensional human body model using Finite Element M ethod is proposed. We focus on deforming the fat of the abdomen and the the butt ocks as an elastic part.

In our method we prepare an core human body model. The core human body model is put fat on to be the surface human body model. We use a patch model to represent a human body model, which represents a surface of a three-dimentional human body by many polygons connected each other. A patc h model can represent a complex surface within arbitrarily small error if it has enough number of patches. The fat is considered as an elastic part, which is subject to Hooke's laws.

The animations with the deformation of a human body model consisting of soft par ts is more realistic than that without deformation.

The deformation of the fat is described by the displacement of vertices of the e lastic part,which is obtained by Finite Element method.

Finite Element Method is a numerical method to solve a partial differential equa tion. Since the equation of motion of the vertices is discribed by a set of part ial differential equations,displacement of vertices of the elastic part for huma n motions is solved by Finite Element Method with matrix calculations.

Here the elastic part is divided into triangle pillars called finite elements. F irst,the element stiffness matrix of each finite element is calculated, then the y are combined to the global stiffness matrix of the elastic part. With the whol e stiffness matrix, we can obtain the displacement of each vertex of the elastic part by matrix calculations.

We applied this method to simulate three human motions: jumping, walking and run ning. And we obtained the animation of each motions. Each animation consists of 8 frames, which is calculated using this method one b y one. We verified if the animations look realistic.

As a result, since a part of fat of the abdomen of a three-dimensional human bod y model is deformed naturally, the animations of jumping and walking looked real istic. But the animation of running was not realistic, because it is not considered tha t human body has a forward-bent posture in case of running. This problem is to b e solved in further research.

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