基於骨幹結構調整之以速寫為基礎的模型動作編輯

動畫的使用在現今的時代是十分常見的，但是要作一個動畫往往需要很多的精力以及很多的時間，而做一個三維的動畫更是被許多人所畏懼，因為它不僅僅需要去規劃所想要表達的動作之外，也需要考慮到三維顯示的複雜性。然而，電腦圖學技術的日益進步使得這些困難的步驟可以更快、更精確的達成，從前好幾天才有辦法作到的事情，現在利用電腦可能只要一分鐘；隨著電影和遊戲的發展，其中動畫變得更加精緻並且更加普及，但了為了加入這些新的技術，近來的三維動畫編輯工具更具有是益複雜的操作介面，也就是說使用者需要花費更多的時間來熟悉三維動畫的編輯過程。雖然說對於專業的使用者而言，這些複雜的操作是必要的，但是對於剛入門的使用者而言，這些過多的操作反而會讓他們害怕退，甚至於失去信心，這樣子反而對於初學者是一種阻礙。所以我們認為一種簡單易懂容易操作的一個三維動作編輯系統是必要的。而為了驅動三維模型來產生動作，以骨幹驅動的三維模型變形是最普遍的方法之一，藉由賦予模型三維的控制骨幹，以及骨幹與模型表面的連接關係，動畫師得以直覺且迅速的操作模型的變形。不過，骨幹的生成以及和模型表面的連接關係的生成是重要卻耗時的，動畫師如何減輕這部份的花費也是一個很重要的議題。針對以上所提出的問題跟需求，我們提出了一個直覺化的三維動作編輯介面，我們的系統自動為輸入的模型生成其骨幹以及骨幹模型表面之間的關聯，接著，使用者可以利用滑鼠速寫的方式來輸入新的骨幹位置，進而驅動模型的變形，然後將變形之後的影格設為關鍵影格，使用者就可以藉由多個關鍵影格來完成一個動畫。因為在變形時可能會有非預期的突起，我們在變形之後會作平滑處理來消去它，但為了保留模型表面的一些特徵，我們使用了一個特別的方法來保留模型表面。另外由於我們的骨幹是自動生成的，也時候未必符合我們的需求，所以我們的系統也提供了使用者增加或減少關節的功能，而在關節處我們也會產生較多的三角形來表示，這樣的話在做變形的時候可以減少因為取樣不夠所造成的錯誤。簡而言之，我們的系統提供了一個直覺操作的介面，由於其便利性跟易學性，初學者可以在幾分鐘之內學會如何操作三維模型的動作，同時在數分鐘之內產生簡短但有趣的三維動畫。

關鍵字

骨幹；調整；速寫；動作編輯

並列摘要

The use of computer animation is very common now, but authoring tools for making these works also increase their complexity to bring in new technologies. 3D computer animation is more difficult because of the complexity of it. So, the user must spend much time to be familiar the tool, and spend much time to edit the computer animation. There are many commercial tools now, but they are very hard to learn because of its complexity. Though as to professional user, the complicated operation is essential. , but as to just non-professional user, these too much operation will let them fear to retreat instead. So we think that it is essential that one user-interface for the non-professional user to user. One of the general solutions for driving the motion of a 3D object is by constructing a skeleton and defining the binding relationship and then adjusting the key-pose of it. skeleton-driven deformation is the one of the common method to drive the deformation of the 3D model, but the generation of the skeleton is hard and time-consuming. Based on the demand of above demands, we introduce an institute 3D animation edit interface. Our system can generate the skeleton of the model and generate the relationship between the skeleton and the surface of the model automatically. We adopted a sketch based input method for accelerating the learning and the editing process. We can easily generate an interesting computer animation by set some key frames by our interface. Because of the artifacts during deformation, some optimization such as smoothing is used, and we used displacement map to preserve the detail of the model. We also can manipulate the structure of the skeleton to fit the model better. This process will make the editing more institute and more interesting , it also can user more triangles to preserve the detail when doing some deformation. As a result, our system provides user a institute interface, which is easy to learn and to do some animation. Non-professional also can be familiar to the system in few minutes, and create simple but interesting animations also in few minutes.

並列關鍵字

skeleton ； manipulation ； sketch ； pose

參考文獻

[SSDZ98] K. Siddiqi, A. Shokoufandeh, S. J. Dickinson, and S. W.Zucker. Shock graphs and shape matching. In Proceedings of the 1998 IEEE International

[WSJZWL92] William J. Schroeder, Jonathan A. Zarge, and William E. Lorensen. Decimation of triangle meshes. Computer Graphics (SIGGRAPH ’92 Proc.), 26(2):65–70, July 1992.

[CTK00] J.-H. Chuang, C.-H. Tsai, and M.-C. Ko. Skeletonization of three-dimensional object using generalized potential field.IEEE Transaction on Pattern Analysis and Machine Intelligence, 22(11):1241–1251, 2000.

[CKB04] Parag Chaudhuri, Prem Kalra., and Subhashis Banerjee. A system for view-dependent animation. Computer Graphics Forum, 23(3):411–420, 2004. (Eurographics 2004 Conference Proceedings).

[DR05] Pose-independent Simplification of Articulated Meshes Christopher DeCoro_ Szymon Rusinkiewiczy Computer Graphics Laboratory Princeton University [I3D 05]

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基於骨幹結構調整之以速寫為基礎的模型動作編輯

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