Effect of observer translation on the relative visual direction of objects

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The optic centre of the camera/eye is at the centre of the white sphere. The rays emerging from the sphere show the visual direction of several distant objects and two near objects (green). As the observer moves (see movie), the visual redirection of the near objects change relative to each other (yellow arcs) and relative to the stable background (blue arcs).
As above, but zoomed in. movie
Translation of the eye/camera causes changes in the relative visual direction of objects (see Figure). In other words, the relative position of objects in the optic array changes as the observer moves his/her head and the extent to which they change depends on the depth of the objects. In fact, the amount by which the relative visual direction of objects change with translation of the camera/eye carries unambiguous information about the distance of the objects[1]. This is quite different from the situation for small fields of view where the 'bas relief' ambiguity arises. Within a small region of the image the same motion could result from a surface with shallow depth relief and a large camera/eye translation or a deeper relief and a small camera/eye translation). This information about the depth of objects can be added to the information about visual direction and surface slant and relief to contribute to a 2$\frac{1}{2}$D sketch as discussed in relation to a small patch.

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References

  1. Glennerster, A., Hansard, M. E., & Fitzgibbon, A. W. (2001). Fixation could simplify, not complicate, the interpretation of retinal flow. Vision Research, 41(6), 815-834.