Abstract: In order to achieve fast collision detection in robot assisted virtual surgery, an algorithm based on changeable direction hull was proposed. It combined fixed direction hull algorithm with the two characteristics in virtual scene, complex motion of surgical instrument end and continuous deformation of soft tissues. Action mode between instruments and soft tissue was analyzed and deformation of soft tissue was predicted. Then the set of box directions was changed to improve the tightness of bounding volume trees. Accordingly, collision detection was accelerated with decreased interaction tests. The simulation results show that collision information can be obtained through the proposed algorithm and the new method implements faster compared with fixed direction hull algorithm.

Key words: virtual surgery, collision detection, changeable direction hull, hierarchical bounding volume, kinematics, fixed direction hull

摘要： 为了实现机器人辅助虚拟手术中快速精确的碰撞检测,提出了基于可变方向凸包的层次包围盒碰撞检测算法。在虚拟场景中,手术器械末端运动复杂多变且软体组织持续形变,分析器械和软组织的作用形式,根据器械运动学参数,预测软组织的变形,将其与固定方向凸包检测方法相结合,通过改变方向向量集合,提高包围盒树的紧密性,进而减少相交测试的次数,加速碰撞检测。仿真实验证明了可变方向凸包的碰撞检测算法可以实现精确的碰撞检测；与固定方向凸包算法相比在快速碰撞检测方面具有优越性，当软组织包含的面片数目越多时,快速性优势越显著。

关键词: 虚拟手术, 碰撞检测, 可变方向凸包, 层次包围盒, 运动学, 固定方向凸包