The distance of objects from the observer and from each other is critical information for, at the very least, navigation.  There are many familiar cues to depth, such as the linear perspective of train tracks receding in the distance, or the aerial perspective of hazy mountains on the horizon.  Our current interest is in hunting down a new cue to depth that may be hidden in the physical structure of the object itself.

Some natural surfaces, such as rocks, are thought to be self-similar, or fractal.  That is, they look the same no matter how far you zoom in or out (a close-up of a rock should look the same as a distant picture of a cliff).  However, it is clear that rock, just as with water, has different structural constraints at different scales, due to the relative dominance of physical forces (surface tension at small scales, mass at larger, for instance).  This structural differences have consequences for the visual appearance of the materials.  We hypothesize that this is an information source, a new cue, about scale and depth that is likely exploited by the visual system.

Related publications:

presentations:

Blaser, E. (2006). The hidden scale of natural forms: A new cue to depth? The Annual Meeting of the Vision Sciences Society (VSS), Sarasota, FL