This dissertation presents a method to transfer the deformation style from one character to another by parameterization of skin deformation for faithful skin deformation. And also presents a method to exaggerate character animation by exaggerating character motion and skin deformation to make more convincing and expressive animation.
For the style transfer of skin deformation, we decompose skin deformation into time-varying signals and basis matrices using dimension reduction techniques, and then approximate the time-varying signals using radial basis functions with respect to joint angles that define skeletal motion. The subsequent parameterization yields a fast and intuitive control of characters and allows us to capture and transfer a derived deformation style to another skeleton-skin structure without considering the input dimension of the deformation data. This style transfer can be used as a basis for realistically animating variants of sample characters who have the same skeletal topology.
Cartoon-style exaggeration can be divided into two parts; exaggeration of skeletal motion and exaggeration of skin deformation. To exaggerate skeletal motion of virtual character, we adopt anticipation and reaction from the principles of traditional 2-dimensional animation techniques. Anticipation and reaction of a motion play a role in exaggerating the motion, because they enlarge the length of the motion path and the amount of movement. To exaggerate skin deformation of virtual character, we use simple mass-spring simulation for each vertex of character skin, to express squash-and-stretch, follow-through and secondary deformation from the principles of traditional animation techniques. Since the simulation of mass-spring is processed on graphics processing unit, we can get the exaggerated and expressive skin deformation results very quickly.
Style transfer and exaggeration methods are implemented and processed on graphics processing unit and they can be used in same time. Therefore we can get the faithful and expressive animation results in real time in the interactive animation environments.