In the era of the metaverse, self-avatars are gaining popularity, as they can enhance presence and provide embodiment when a user is immersed in Virtual Reality. They are also very important in collaborative Virtual Reality to improve communication through gestures. Whether we are using a complex motion capture solution or a few trackers with inverse kinematics (IK), it is essential to have a good match in size between the avatar and the user, as otherwise mismatches in self-avatar posture could be noticeable for the user. To achieve such a correct match in dimensions, a manual process is often required, with the need for a second person to take measurements of body limbs and introduce them into the system. This process can be time-consuming, and prone to errors. In this paper, we propose an automatic measuring method that simply requires the user to do a small set of exercises while wearing a Head-Mounted Display (HMD), two hand controllers, and three trackers. Our work provides an affordable and quick method to automatically extract user measurements and adjust the virtual humanoid skeleton to the exact dimensions. Our results show that our method can reduce the misalignment produced by the IK system when compared to other solutions that simply apply a uniform scaling to an avatar based on the height of the HMD, and make assumptions about the locations of joints with respect to the trackers.

翻译：在元宇宙时代，自我化身日益普及，能够增强用户在虚拟现实中的临场感与具身性，同时在协作式虚拟现实中通过手势改善沟通。无论采用复杂的动作捕捉方案，还是基于少量跟踪器与逆运动学（IK）的方案，都要求化身与用户体型高度匹配，否则用户可能会察觉到自我化身姿态上的明显偏差。为实现精确的尺寸匹配，传统方法通常需要手动完成，且需由第二人测量用户肢体尺寸并录入系统。这一过程既耗时又易出错。本文提出一种自动测量方法，用户只需佩戴头戴式显示器（HMD）、两只手柄控制器和三个跟踪器，完成一组简单动作即可。该方法能以低成本快速自动提取用户身体尺寸，并将虚拟人形骨架调整至精确比例。实验结果表明，与仅根据HMD高度对化身进行统一缩放并假设关节与跟踪器相对位置的方案相比，本方法能有效减少IK系统产生的姿态对齐误差。