我們提出一個新的三維動作資料檢索系統，使用手繪介面畫出人物肢體的動作路徑和關鍵姿勢做為輸入，以類似卡通漫畫當中描述動作的方式來進行資料庫檢索，不需要使用鍵盤輸入文字或是產生一個新的動作資料做為輸入，而只要繪畫簡單的二維線條，提供使用者以更方便且直覺的操作方法，快速的從動作資料庫中將目標動作取出。系統會利用人物骨架的資訊，讓使用者在單一視角下以二維的筆觸，產生出三維的曲線做為各關節點的動作軌跡。我們計算出動作資料每個關節點在時間軸上不同位置所形成的軌跡，將資料庫當中的動作資料轉為以多個曲線來表示。藉由比對軌跡的方式，讓使用者輸入的二維筆觸和資料庫當中的動作資料得以比較，此外可免去在傳統動作資料檢索系統當中費時的時間對齊程序。比較軌跡時，我們利用球諧波函數(Spherical Harmonic Functions SHFs) 將曲線轉到頻率域，以少數的係數來表示原先複雜的動作資料，大幅降低資料的維度，可以加快資料比較的速度。我們的系統可以輸入數個代表不同動作的關鍵姿勢和筆觸，將搜尋到的各個動作做串連，可產生一個有趣且內容豐富的三維動畫。

We introduce a novel system for rapidly retrieving target motion from a large motion database. Most previous works often request the user to pick a motion clip from a database or even from a motion capture (MOCA) system as query input, while our system simply request the user to sketch some motion strokes on a blank canvas with a selected articulated figure. A natural pen-and-paper like sketching interface is proposed to provide novel query input to 3D motion database. In the spirit of our scenario, the user sketches some motion strokes on a selected character in a single view to query motion. This is more analogues to our experience with drawing using pen and paper on a blank canvas in traditional comics. In this thesis, the motions in the database and 2D hand-drawn strokes are represented by a complete set of orthonormal, spherical harmonic basis functions (SHFs). With this compact encoding, the spatiotemporal variances of motions and strokes are represented by only a few coefficients of SHFs. This new representation of motion trajectories can avoid computationally-intensive time-alignment which is a common routine in many previous works. Furthermore, the similarity measurement can be computed efficiently by simply matching the coefficients of SHFs in a hierarchical manner. Therefore, our system has a good potential to real-time answering the queries. Finally, we also demonstrate an application of the proposed system to generate interesting 3D animation from 3-5 frame hand-drawn comic strips.

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