以滑鼠速寫為基礎的三維動作編輯介面

Abstract

隨著電腦圖學技術的日漸茁壯，電影以及電腦遊戲中的動畫也變得更加精緻並且更為普及。然而為了加入新的技術，近來的三維動畫編輯工具更具有日益複雜的操作介面。這意味著入門使用者將需要花費更多的時間來熟稔三維動畫的編輯過程。為此我們需要一個具備了簡單易用的操作方法以及精簡的使用者介面的編輯系統以引領初學者進入三維電腦動畫的大門。為了驅使三維模型產生動作，以骨幹驅動的三維模型變形是最普遍的方法之ㄧ。藉由賦予模型三維的控制骨幹以及指定骨幹與模型表面之間的連接關係，動畫師得以調整其關鍵影格動作。然而即使各個步驟都極為耗時，動畫師仍需為每一個具有動作的模型手動產生以上所有資訊。這些過程顯得十分繁瑣，特別在當其僅須表達一些初步的構思的時候。為此，減輕花費在指定骨幹及連接關係的時間與勞力亦是十分重要的議題。 針對以上所提出的需求，我們提出了一個直覺化的三維動畫編輯介面。在我們的系統中採用了以滑鼠速寫為基礎的輸入方式來增進系統的易用性以及易學性，並結合了自動產生的骨幹以及連接關係資訊使得使用者得以省略以骨幹驅動三維模型變形的準備工作。在前者中我們將骨幹以三維曲線以及特徵點表示並使其依照使用者輸入的畫筆軌跡產生變形。同時並利用編輯曲線影子的外型以調整三維曲線的深度資訊來幫助使用者更易於編輯三維曲線。而在後者之中為了使變形的結果更加使人滿意我們利用了平滑化來消去變形中可能產生的非預期突起。對於表面原本就凹凸不平的三維模型我們更採取了特殊處理以避免其表面特徵被平滑化的動作去掉。以結果而言，我們的系統提供了高度的使用便利性以及易學性。初學者可以在數分鐘之內學會如何編輯三維模型的動作，同時在數分鐘內產生簡短但有趣的三維動畫。

As computer graphics grows its capability, movies and video games consist of computer animations obtained quality improvement and become more popular. However, authoring tools for making these works also increase their complexity to bring in new technologies. That means ovices for 3D animation have to take more training to join into the industry. Systems with simpler control manner and more concise user interface are needed to introduce them into the palace hull of computer animation. 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. Even each stage is time consuming, the artist must repeat the three stages on every model which needs to be animated. The procedure is annoying especially when he just want to present some primary ideas. For this reason, reducing the time and effort spent in each stage is also important. Based on the demands we mentioned above, an intuitive user interface for animation authoring is introduced. We adopted a sketch based input method for accelerating the learning and also the editing process, and provides automatic skeleton and binding weight generation to omit the preparation needed for skeleton driven key-pose editing. To the former, the skeleton is represented as feature points connected with NURBS and deformed according to the input stroke of the user. Technique for assisting the procedure of editing 3D curve by changing the shadow appearance is also introduced. To the latter, some optimization such as smoothing is adopted to make the deformed result more pleasant. Additional treatment for model with lumpy surface called ‘dual-resolution meshes’ is taken to prevent the detail feature from eliminated by the smooth operator. As a result, our system provides great facility in editing and quite simplicity in learning. Users could pick-up the system in few minutes and create simple but interesting animations also in few minutes.