Skeleton-driven Animation Transfer based on Consistent Volume Parameterization

隨著多媒體技術的日新月異，藉由電腦動畫創造的虛擬角色在數位產業中也有越來越受到重用的趨勢。然而在實務上，當動畫師要為一個虛擬角色創作一連串的動畫時，除了設計其三維模型之外還要為其製作骨幹、設定骨幹與表面間的影響係數、以及編輯每一個時間點的姿勢。這些工作可以說是非常繁雜而瑣碎的。尤其當動畫師要為一大群虛擬角色編輯類似的動作時，更往往需要重複進行許多同樣的工作。 因此，我們提出一個以減輕動畫師負擔為目標的系統。這個系統讓使用者輸入一個已經編輯好動畫的虛擬角色，以及一個還沒有任何動畫資訊的三維模型。接著，使用者只需要在模型上標示出兩兩對應的特徵點位置，系統即能自動建立模型之間的同步表面參數化，進而延伸得到兩者之間的體積對應關係。利用這些對應關係，系統得以將來源角色的動作轉移到目標角色身上，至此便完成了三維模型的骨幹動畫轉移工作。 透過此系統所產生的目標角色動畫，因為已經有了完整的骨幹、影響係數、動畫姿勢等等資訊，且可以相容於實務上常用的動畫製作軟體中，因此動畫師不需要額外的設定，就可以馬上再為這個角色創作其他動畫片段。除此之外，只要透過簡單的複製以及對時間軸參數的調整，動畫師就能藉由我們系統的幫助來打造含有大量角色的動畫場景。這些應用都能大幅降低動畫師製作角色動畫時所需的時間與精力。To edit or create the animation of a 3D character model has always been an important but time-consuming task, since the animator usually needs to set up the character's skeleton, paint its binding weights, and adjust its key-poses. Therefore, systems and algorithms have been proposed to improve the animating pipeline in both efficiency and quality concern. Hence, we propose an animation transfer system in this thesis to take a well-edited character animation as the input. Then, the system can transfer the skeleton, binding weights, and other attributes of the given character model to another static model with only few corresponding feature points specified. The transferring process is based on a mapping between the space around two character meshes. In this thesis, the mapping is called consistent volume parameterization, which inherits consistent surface parameterization. With this method, the skeleton, binding weights, and other attributes transferred by our system are nicely generated and ready to be edited. Hence, the animator can start to create a skeleton-driven animation for the new character model without any prior setting. Moreover, our system is also capable of cloning a skeleton-driven animation to several other character models which can be used in a crowd animation.1 Introduction 8 1.1 Motivation . . . . . . . . . . . . . . . . . . 8 1.2 Overview . . . . . . . . . . . . . . . . . . . 11 1.3 Contribution . . . . . . . . . . . . . . . . . 12 1.4 Organization . . . . . . . . . . . . . . . . . 13 2 Related Work 15 2.1 Surface Parameterization . . . . . . . . . . . 15 2.2 Consistent Surface Parameterization . . . . . .15 2.3 Volume Parameterization . . . . . . . . . . . 17 2.4 Model Editing . . . . . . . . . . . . . . . . 18 3 System Overview 22 4 Animation Data 24 4.1 Skeleton . . . . . . . . . . . . . . . . . . . 24 4.2 Binding Weights . . . . .. . . . . . . . . . . 26 4.3 Key-Frame Poses . . . . . .. . . . . . . . . . 27 5 Consistent Surface Parameterization 29 5.1 Feature Point Speci‾cation . . . . . . . . . . 30 5.2 Base Domain Construction . . . . . . . . . . . 30 5.3 Inter Surface Parameterization . . . . . . . . 35 6 Consistent Volume Parameterization 37 6.1 Mean Value Coordinates . . . . . . . . . . . . 37 6.2 Volume Mapping . . . . . . . . . . . . . . . . 38 7 Animation Transfer 42 7.1 Skeleton Transfer . . . . . .. . . . . . . . . 42 7.2 Binding Weights and Motion Data Transfer . . . 44 8 Results 46 8.1 Performance . . . . . .. . . . . . . . . . . . 47 8.2 Consistent Surface Parameterization . . . .. . 48 8.3 Consistent Volume Parameterization . . . . . . 50 8.4 Animation Transfer . . . . . . . . . . . . . . 51 8.5 Crowd Animation . . . . .. . . . . . . . . . . 52 9 Conclusions and Future Work 63 Bibliography 6