Optic flow can be defined as the motion of all the surface elements from the visual world. As you move through the world, the objects and surfaces within the visual environment flow around you. The human visual system can determine your current direction of travel from the movement of these surfaces.

See Optic Flow animations>>
 

The interactive optic flow demo shows how all the tiny bits of texture that define the surfaces of the ground and objects on the world could be used to tell direction of locomotion. When optic flow information hits the back of the eye it is called retinal flow (RF).

Besides retinal flow there are also other sources of information that can assist the observer:

        -The angle at which you orient your head and eyes when looking to a steering target (extra-retinal information) 

        -The visual direction (VD) of a target relative to a reference feature such as a windscreen.  

Our research has been assessing the degree to which observers/drivers rely upon retinal flow (RF), visual direction (VD) and extra-retinal (ER) information for different steering tasks. One technique we use is to spin the ground as you locomote within a computer simulated environment, thereby introducing a systematic bias to the RF information (without changing VD or ER).  We have shown that even with a visual marker you cannot steer accurately to a target if the ground is being rotated (Wilkie & Wann, 2002, 2003).

Further information on Optic Flow can be found in the conferences section >>

Department of Psychology, Royal Holloway, University of London, Egham, Surrey TW20 0EX
Tel/Fax : +44 (0)1784 443526/434347