Abstract
Perceiving 3D shape involves processing and combining different cues, including texture, shading, and specular reflections. We have previously shown that orientation flows produced by the various cues provide fundamentally different information about shape, leading to complementary strengths and weaknesses (see Cholewiak & Fleming, VSS 2013). An important consequence of this is that a given shape may appear different, depending on whether it is shaded or textured, because the different cues reveal different shape features. Here we sought to predict specific regions of interest (ROIs) within shapes where the different cues lead to better or worse shape perception. Since the predictions were derived from the orientation flows, our analysis provides a key test of how and when the visual system uses orientation flows to estimate shape. We used a gauge figure experiment to evaluate shape perception. Cues included Lambertian shading, isotropic 3D texture, both shading and texture, and pseudo-shaded depth maps. Participant performance was compared to a number of image and scene-based perceptual performance predictors. Shape from texture ROI models included theories incorporating the surface's slant and tilt, second-order partial derivatives (i.e., change in tilt direction), and tangential and normal curvatures of isotropic texture orientation. Shape from shading ROI models included image based metrics (e.g., brightness gradient change), anisotropy of the second fundamental form, and surface derivatives. The results confirm that individually texture and shading are not diagnostic of object shape for all locations, but local performance correlates well with ROIs predicted by first and second-order properties of shape. The perceptual ROIs for texture and shading were well predicted via the mathematical models. In regions that were ROI for both cues, shading and texture performed complementary functions, suggesting that a common front-end based on orientation flows can predict both strengths and weaknesses of different cues at a local scale.
Meeting abstract presented at VSS 2014