Computational Modeling of Depth-Ordering in Occlusion through Accretion or Deletion of Texture

Harald Ruda¹, Gennady Livitz², Guillaume Riesen³, Ennio Mingolla4
¹Northeastern University, ²Northeastern University, ³Northeastern University, 4NortheasternUniversity

Understanding the depth-ordering of surfaces in the natural world is one of the most fundamental operations of the primate visual system. Surfaces that undergo accretion of deletion (AD) of texture are always perceived to behind an adjacent surface.

An updated ForMotionOcclusion (FMO) model (Barnes and Mingolla, 2013) includes two streams of computing motion signals and boundary signals. The two streams generate depth percepts such that AD signals together with boundary signals generate a farther depth on the occluded side of the boundary. The model fits the classical data (Kaplan, 1969) as well as the observations that moving surfaces tend to appear closer in depth (Royden et al., 1988), for both binary and grayscale stimuli.

The recent ‘Moonwalk illusion’ described by Kromrey et al. (2011) upends the classical view that the surface undergoing AD always becomes the background. Here surface that undergoes AD appears to be in front of the surrounding surface; as a result of the random flickering noise in the surround. As an additional challenge, we developed an AD display with dynamic depth ordering. A new texture version of the Michotte rabbit hole phenomenon (Michotte, Thinès, & Crabbè, 1964/1991) generates depth that changes in part of the display area. We will show simulations that explain the workings of the new version of the model. The model now uses a simplified push-pull mechanism to generate depth-order signals, it is able to explain the counter-intuitive Moonwalk stimulus. We will show detailed simulations explaining the Moonwalk illusion as well as the textured Michotte rabbit hole phenomena.

Keywords: Modeling, Motion, Depth-Order, Accretion


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