Other monocular cues

**Figure 6.7:** Several more monocular depth cues: (a) *Shadows* resolve ambiguous depth in the *ball and shadow illusion*. (b) The *interposition* of objects provides an ordinal depth cue. (c) Due to *image blur*, one gnome appears to be much closer than the others. (d) This scene provides an *atmospheric cue*: Some scenery is perceived to be further away because it has lower contrast.
$\begin{figure}\begin{center} \begin{tabular}{cc} \psfig{file=figs/floatingballs.... ...ric.ps,width=2.6truein} \\ (c) & (d) \\ \end{tabular}\end{center} \end{figure}$

Figure 6.7 shows several other monocular cues. As shown in Figure 6.7(a), shadows that are cast by a light source encountering an object provide an important cue. Figure 6.7(b) shows a simple drawing that provides an ordinal depth cue called interposition by indicating which objects are in front of others. Figure 6.7(c) illustrates the image blur cue, where levels are depth are inferred from the varying sharpness of focus. Figure 6.7(d) shows an atmospheric cue in which air humidity causes far away scenery to have lower contrast, thereby appearing to be further away.