> In the real world, we have an intuitive understanding of how big something should be and if we see two objects that look the same size, but if we know that th

> In the real world, we have an intuitive understanding of how big something should be and if we see two objects that look the same size, but if we know that they aren’t, we infer that one object is more distant than the other. I see your point. As a painter, physiology and perception play as significant role in my treatment of space as perspective. My original quibble was that these terms are being confused with each other. We infer space from many cues. When I paint a pastoral landscape (e.g. trees on a hill) I create depth by employing a whole lot of spatial devices. Most significantly by considering the depth planes (foreground, middle ground etc) and their relative differences. These differences can be of average lightness, local contrast (i.e. dynamic range), edge sharpness (distant objects tend to be more fuzzy), hue (distant objects tend to be more blue) etc etc. None of these have anything to do with perspective. However, the moment I paint a building, it is 90% an issue of perspective. Perspective is a device for projecting cubes onto a picture plane. The 3 points of 3 point perspective relate to the three visible sides of the cube. It is a mechanical process entirely within the domain of physics. This is why Ibn al-Haytham's treatise on optics simultaneously addressed perspective. > Yes I’m self aware enough to know that my opinions come from one semester in art class over 25 years ago. Its seems that it was a fruitful semester. :)