Digital Signal Processing Reference
In-Depth Information
Figure 6.5
Aerial perspective
the horizon to appear in faded colours or washed in lower light luminance
and contrast, while objects that are near appear to have vibrant or intense
colours with strong contrast. For example, Figure 6.5 shows the mountains
in the horizon always look slightly bluish or hazy. The reasons for this are
small water and dust particles in the air between the eye and the mountains.
The further away the mountains, the hazier they look.
ShadesandShadows
The shadow monocular depth cue has several rules:
•
If an object is solid, it casts a shadow.
•
If there is only one light source, then all shadows fall in the same direction
and the shadow is opposite from the source of light.
•
Objects with shadows falling on them are further away than objects casting
the shadow.
•
If the object is lower than the 'ground plane' (such as a well), the shadow
appears on the same side as the source of light.
When we know the location of a light source and see objects casting
shadows on other objects, we learn that the object shadowing the other is
closer to the light source. As most illumination comes from above, we tend to
resolve ambiguities using this information. The three-dimensional looking
computer user interfaces are a nice example of this. Also, bright objects
seem to be closer to the observer than dark ones. It is clearly visible in the
Figure 6.6.
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