Purchase this article with an account.
M. Fluckiger, B. Baumberger; Estimation of a Texture Velocity Projected on the Ground Surface . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4087.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The aim of this research is to study the perception of the velocity of an optic flow. The flow is projected on a large floor (5 x 10 m) on which the participants stand upright. In this kind of situation they must in fact estimate an optical velocity gradient. The Texture Flow Generator (TFG), that projected a moving texture of circular luminous dots on the ground, was the same as the one used to record produced speed in locomotor performances in previous experiments. Methods: In 3 experiments with different psychophysical methods, subjects had to reproduce, with a joystick, the visual speed presented in different gaze position. Results: The values of differential thresholds are comprised between 10 and 20 % and increase with global optical velocity. No significant effect is observed from the different gaze positions. These thresholds are much higher than those observed in an adjustment of the speed of locomotion in the same optical environment. Conclusions: The results demonstrate that the estimation of the velocity of a texture when standing still (as in the present experiments) involves a different perceptual processing than when perception is coupled with a displacement of the participants as in walking. Moreover, the data do also hint at the difficulty to extrapolate from classical psychophysical results, obtained with small vertical screens and homogeneous textures, to the perception of optical flow in a large visual environment.
This PDF is available to Subscribers Only