Abstract: This article studied the application of cubic-spline to realize the velocity control along specified path in visual simulation system.In this system，arc length of the curve between two points is calculated by Simpson method，and then observer’s position and orientation at every frame are deduced by bisection.In order to realize real time velocity control of observer in virtual environment，storing data of the current frame’s position and setting appropriate iteration precision were addressed so as to decrease the calculation for getting observer’s position and orientation of next frame.This algorithm has good effect in practice and has been applied successfully in urban mass transit simulation system．

Key words: visual simulation, virtual reality, spline curve, arc-length integration

摘要： 在视景仿真系统中，利用三次样条曲线实现固定路径浏览中速度实时控制。通过Simpson法计算两点之间曲线弧长，二分法迭代得到观察者每一帧时所处的视点和视角。为达到虚拟环境中的实时性要求，提出了保存观察者当前帧所处视点和设定适当的迭代精度，从而降低得到下一帧观察者视点和视角所需的计算量，实现观察者运行速度的实时性控制。该方法在实际仿真中取得了较好的效果，并已成功应用于某城市轨道交通视景系统中。

关键词: 视景仿真, 虚拟现实, 样条曲线, 弧长积分