New Method For 3D Animating By Examples

Computer Animation creates vivid pictures based on Computer Graphics & Image, Art, Mathematics, Physics and other relative subjects. It provides revolutionary method by which people can simulate the change of 3D world. It has been widely used in television, industrial, advertisement and entertainment industries and influences the living of people profoundly. Two fundamental problems in Computer Animation are: (1) How to create great amount of computer animations effectively and economically? and (2) How to reuse the large numbers of existing computer animations effectively?Traditional animation technologies include parametric key frame technology, path-driven anminations, morphing and procedural animations. Some excellent animation softwares have implemented these technologies and have been used commercially. However, the uses of these softwares are limited to a set of trained experts, and easy-to-use interactive modeling and animating is still a challenge topic. On the other hand, 3D sketching programs are good for novices, but their functionalities are very limited only for simple meshes or animations practically. At the same time, despite the tremendous amount of artistic, skillful, and time consuming animation crafts existed, there are few techniques to help with their reuses.With the goal that even non-experts can create authentic 3D animations quickly and easily from existing source animations, in this thesis, we propose a sketch based synthesis approach to create 3D animation of a target character. Our approach consists of the following steps: (a) providing a sketch based mapping between the sources and the target; (b) deforming the target based on the deformations of the corresponding sources by means of differential mean value coordinates; (c) smoothing the deformed target with constrained minimization method to form a key frame of the target animation; and (d) interpolating between key frames created from (c) to produce a complete 3D animation of the target. In addition, based on the above technologies, we develop a mesh based inverse kinematics technology so that user can adjust the results interactively while keeping the original styles of source animations unchanged. We provide new research contributions on all these topics, and integrate them into our newly developed prototype animating system. Our approach is general and does not require the sources and target to share the same number of vertices or triangles, or to have matching connectivity. In our system, source animations can be 3D animations as well as 2D videos or macromedia flashes; and the target can even be unstructured orpoint cloud. Our approach is intuitive and is able to produce highly authentic 3D animations. We demonstrate our approach by constructing a full cart animation from dog, cat, snake and human animations as well as applying a 2D video of the wheel of a car onto the wheels of the cart. Other examples produced from our prototype system are also given in the paper to illustrate the generality and robustness of our approach. Specifically, we make the following contributions in the thesis: Developed a new sketch based method to create the correspondence betweenthe source meshes and the target mesh; Extended mean value coordinates for closed triangular meshes developed into mean value coordinates for unclosed (open) triangular meshes to represent the deformation of meshes; Developed an affine matrix based method for computering deformation andsynthesizing deformation; Developed a method which maps 2D animations to 3D character, Proposed a set of affine matrix based smoothing constraint functions whichcan deal with unstructured data, e.g. point cloud. Proposed a multi-mesh based inverse kinematics; Developed a fast trapeziums based method for shadow volumes to improvethe reality of resulting 3D animation; Implemented the above methods to develop a new integrated 3D animatingprototype system.The dissertation is organized as follows. After introducing some backgrounds and the state of art of computer animation in Chapter 1, we introduce sketch based correspondence creating method in Chapter 2; Chapter 3 describes the deformation transfer technology; Chapter 4 introduces some postprocessing technology of 3D animation; Chapter 5 introduces the mesh based interactive 3D animation creating method; Chapter 6 describes our integrated 3D animating prototype system and illustrates some experiment results; Finally, we conclude this dissertation and discuss some directions for future work.