An Ames room is constructed so that from the front it appears to be an ordinary cubic-shaped room.
But this is a trick of perspective and the true shape of the room is trapezoidal: the walls are slanted and the ceiling and floor are at an incline, and the right corner is much closer to the front-positioned observer than the left corner (or vice versa).
As a result of the optical illusion, a person standing in one corner appears to the observer to be a giant, while a person standing in the other corner appears to be a dwarf. The illusion is convincing enough that a person walking back and forth from the left corner to the right corner appears to grow or shrink.
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VIDEO Ames Room
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Ames Room 3D demonstration
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Explaination : How Ames Room Works??
When you look (through a peephole -- to remove any cues from stereopsis) into an Ames Room, the room looks normal and cubic, but its true shape is cleverly distorted. The floor, ceiling, some walls, and the far windows are actually trapezoidal surfaces. Although the floor appears level, it is actually at an incline (the far left corner is much lower than the near right corner). The walls appear perpendicular to the floor, although they are actually slanted outwards.
This diagram shows how the Ames Room forms an identical image of a normal cubic room on your retina. If a straight line (representing a ray of light) is drawn from one corner of an imaginary cubic room to your eye, the corner can meet this ray at any point along its length and still appear cubic.
Since the two visible corners of the room subtend the same visual angle to the eye through the peephole, the two corners appear to be the same size and distance away. The left corner, however, is actually twice as far away as the right corner. When the view sees the room from another angle the true shape of the room is revealed.
The retinal image produced by the distorted room is identical with (and therefore indistinguishable from) that of a normal cubic room. In fact, there are an infinite number of possibilities that will give rise to this same retinal image.
The Size Illusion
When you look through a peephole into an Ames Room, a person seen standing in the left corner will always appear substantially smaller than when seen standing in the right corner. The person looks too small because the image is smaller than what would be expected for the apparent distance of that part of the room. The illusion of normality is so convincing that as the person is seen walking about the room, he or she appears to be growing and shrinking rather than approaching and receding.
The generally accepted explanation for the Ames Room size illusion is that the apparently cubic perspective overrides your perception of size constancy. In other words, the size illusion is somehow caused by the strange shape of the room (A rather peculiar explanation, since one does not normally have such effects when walking into oddly designed rooms).
Seckel and Klarke have shown, however, that the room contributes little (if only charm) to the illusion. By using scale models, they found that only an apparently horizontal path against a perspective background is necessary to produce the size illusion. The figure's relative height (or elevation to the apparent horizon is what's important). The room (walls and ceiling) can be omitted.
While the additional apparent perspective lines are among several factors enhancing the illusion, their main affect is to hide correct perspective cues, not to create the illusion. In addition, the perspective cue of relative head height is not significant, compared to ground level.
In the Ames Room, the person appears to travel along an apparently horizontal and level surface. There is no observed rise in relation to the horizon as the figure recedes.
This is important, because a figure receding on a level surface will rise in the visual field, given the fixed relative position of the viewer and the figure.
On a level surface as someone recedes into the distance the level of their feet rise and the level of their head lowers in relation to a true horizontal.
