Motion and texture shape cues modulate perceived material properties.

Specular and matte surfaces can project identical images if the surface geometry and light field are appropriately configured. Our previous work has shown that the visual system can exploit stereopsis and contour cues to 3D shape to disambiguate different surface reflectance interpretations. Here, we test whether material perception depends on information about surface geometry provided by structure from motion and shape from texture. Different surface textures were superimposed on a fixed pattern of luminance gradients to generate two different 3D shape interpretations. Each shape interpretation of the luminance gradients promoted a different experience of surface reflectance and illumination direction, which varied from a specular surface in frontal illumination to a comparatively matte surface in grazing illumination. The shape that appeared most specular exhibited the steepest derivatives of luminance with respect to surface orientation, consistent with physical differences between specular and diffuse reflectance. The effect of apparent shape on perceived reflectance occurred for a variety of surface textures that provided either structure from motion, shape from texture, or both optical sources of shape information. In conjunction with previous findings (Marlow, Todorović, & Anderson, 2015; Marlow & Anderson, 2015), these results suggest that any cue that provides sufficient information about 3D shape can also be used to derive material properties from the rate that luminance varies as a function of surface curvature.