人机交互技术3—输入设备.pptx

Input Devices Tracker: some hardware to measure (or to track) the position and orientation of an object in real-time. Typical objects for tracking include the head, hands, and limbs of the user. The tracked position and orientation are typically relative to a reference coordinate system. 1. 3D Position Trackers Accuracy Jitter Drift Latency Tracker performance is typically measured using the following parameters: 1.1 Accuracy Accuracy refers to the similarity of the object’s actual position and the measurement by the tracker. It is typically not a constant and it degrades with distance from the origin of the reference coordinate system. The distance at which the accuracy is acceptable defines the tracker’s operating range. 1.2 Jitter（震动） Jitter refers to the changes in tracker output when the tracked object is stationary. These changes are typically random and fluctuate（波动） around the true value. The amount of jitter changes over the tracker workspace, and is influenced by environmental conditions. 1.3 Drift（漂移） It may require periodically resetting the error by some secondary tracker. Drift refers to the inaccuracy that grows as time passes, due to factors such as error accumulation. 1.4 Latency In the case of a 3D tracker, latency refers to the time between the change in object position or orientation and the time the sensor outputs it. Large delay between the motion and the visual feedback causes simulation sickness, such as headaches, nausea（恶心）, and dizziness（眩晕）. Latency refers to the time delay between the moment of action and that of receiving the signal. Possible methods to reduce the latency: Using faster communication lines. Synchronizing the tracker measurement, communication, rendering, and display loops. This will help reduce the update rate of the whole system. 2. Tracker Update Rate This is the number of measurements that the tracker reports every second, typically over 30. The larger this update rate is, the better the dynamic response of th