隨著物理模擬技術的成熟，目前相當多電影與遊戲都加入物理模擬技術，使物件之間互動更為自然。但是要在三維物理模擬環境下，重現動作捕捉器動畫相當困難，因為不容易維持模擬人體的平衡。
本篇論文提出新方法，可以在物理模擬環境下，即時(real-time)控制三維兩腳角色重現目標動作捕捉器動畫，並動態對外界影響做出反應。本篇論文是利用倒單擺代表整個人體，並即時去改變動作路徑，使模擬人體身體與動作捕捉動畫人體維持相同的狀態。除了重現動作捕捉器記錄下來的動畫外，在不同的地形與外力影響下，亦可維持平衡。此外，用於控制人體做出目標姿勢的技術中，最常見的控制技術是比例微分控制器(Proportional - Derivative controllers)。但是此種控制器需要微調參數，不同動作的參數皆不同。因此本篇論文提出一個速度驅動控制器(velocity-driven)，只需要粗略設定一組參數，即可做出各種類型的動畫。
本篇論文提出的控制器，可以在即時(real-time)運算下，控制模擬的人體跟隨目標動畫。並可以隨時改變地形、給予外力、改變姿勢，或使用者給予的動作限制，皆可立即(real-time)反應在模擬人體上，並保持平衡。

This paper present a physics-based approach to generate 3D biped character animation that can react to dynamical environments in real-time. Our approach utilizes an inverted pendulum model to on-line adjust the desired motion trajectory from the input motion capture data. This on-line adjustment produces physically-plausible motion trajectory adapted to dynamic environments, which is then used as the desired motion for the motion controllers to follow in dynamics simulation. Rather than using the Proportional-Derivative controllers whose parameters usually cannot be easily set, our motion following control adopts a velocity-driven method which computes joint torques based on the desired joint angular velocities. Physically-correct full body motion of the 3D character is computed in dynamics simulation using the computed torques and dynamical model of the character. Our experiments demonstrate that MOCAP-following with real-time response animation can be achieved easily. Besides, physically-plausible motion style editing and automatic motion transition can also be generated naturally.

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