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Laurence R. Harris, Richard T. Dyde, Michael R. M. Jenkin; Where's the floor?. Journal of Vision 2006;6(6):731. doi: 10.1167/6.6.731.
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© ARVO (1962-2015); The Authors (2016-present)
The floor of a room is the surface that is most likely to provide support. What is the contribution of the room's structural features to the perception of which surface this is?
Using the Immersive Visual Environment at York (IVY) twelve subjects were placed in three simulated box-like rooms with no features. The rooms had a constant depth, a height-to-width ratio that varied from 1:1 to 1:3 and were presented at different roll orientations in an interleaved manner. The far wall was coloured purple and the other four visible surfaces were randomly assigned one of four colours on each trial and subjects indicated ‘the floor’ by pressing correspondingly coloured buttons on a game-pad. Each surface was described by its normal vector. The vectors of the chosen surfaces were summed to provide the average orientation of the perceived floor for each room orientation.
We tested three models of how people determine the floor. Subjects might choose the surface (1) closest to orthogonal to gravity (flipping point of wall-to-floor at 45°), (2) closest to orthogonal to gravity on each side of the room's diagonal (flipping point when diagonal of room vertical), or (3) based on a weighting function dependent on each surface's length and orientation. Contrary to expectations, subjects did not necessarily choose the surface closest to orthogonal to gravity. The weighted-surface model best described the data with each surface being weighted by its relative length raised to the power 1.25 (r2 = 0.9).
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