Warren W H, Blackwell A W, Kurtz K J, Hatsopoulos N G, Kalish M L
Department of Psychology, Brown University, Providence, RI 02912.
Biol Cybern. 1991;65(5):311-20. doi: 10.1007/BF00216964.
All models of self-motion from optical flow assume the instantaneous velocity field as input. We tested this assumption for human observers using random-dot displays that simulated translational and circular paths of movement by manipulating the lifetime and displacement of individual dots. For translational movement, observers were equally accurate in judging direction of heading from a "velocity field" with a two-frame dot life and a "direction field" in which the magnitudes of displacement were randomized while the radial pattern of directions was preserved, but at chance with a "speed field" in which the directions were randomized, preserving only magnitude. Accuracy declined with increasing noise in vector directions, but remained below 2.6 degrees with a 90 degrees noise envelope. Thus, the visual system uses the radial morphology of vector directions to determine translational heading and can tolerate large amounts of noise in this pattern. For circular movement, observers were equally accurate with a 2-frame "velocity field", 3-frame "acceleration" displays, and 2-frame and 3-frame "direction fields", consistent with the use of the pattern of vector directions to locate the center of rotation. The results indicate that successive independent velocity fields are sufficient for perception of translational and circular heading.
所有基于光流的自我运动模型都将瞬时速度场作为输入。我们使用随机点显示对人类观察者测试了这一假设，该显示通过操纵单个点的寿命和位移来模拟平移和圆形运动路径。对于平移运动，观察者从具有两帧点寿命的“速度场”和“方向场”判断航向方向时同样准确，在“方向场”中位移大小是随机的，但方向的径向模式得以保留，而从“速度场”判断时则是随机猜测，在“速度场”中方向是随机的，仅保留大小。随着矢量方向噪声的增加，准确性下降，但在90度噪声包络下仍保持在2.6度以下。因此，视觉系统利用矢量方向的径向形态来确定平移航向，并且能够容忍这种模式下的大量噪声。对于圆周运动，观察者在两帧“速度场”、三帧“加速度”显示以及两帧和三帧“方向场”下同样准确，这与利用矢量方向模式来定位旋转中心是一致的。结果表明，连续的独立速度场足以用于感知平移和圆周航向。
