Abstract
The perception of a glossy surface in a static monochromatic image occurs when a bright highlight is embedded in a compatible context of shading and a bounding contour. Although some studies address perception of gloss for whole objects, an observer may adopt an attitude of scrutiny in viewing a glossy surface, whereby the impression of gloss is partial and non-uniform at image regions at some distance from a highlight.
We investigated differential perception of gloss within a single object by using a rating scale and small probe points to indicate image locations. Experimental factors included luminance near highlights, highlight size, surface curvature and surface discontinuity.
Observers' gloss ratings were never uniform across a surface, but decreased as a function of a distance from a highlight. Rated gloss was not a function of the luminance near the probe point, however. When, by design, the distance from a highlight was uncoupled from the luminance value at corresponding probe points, the decrease in gloss ratings depended on distance and not on luminance level. Experiments with surfaces of a different curvature indicate that gloss ratings changed as a function of estimated surface distance or distance in depth, rather than as a function of the image distance of probe points from a highlight.
Also, surface continuity between a highlight and the probe point is important for the full propagation of perceived gloss.
Supported in part by: ONR N00014-01-1-0624 and AFOSR F49620-01-1-0397.