How does the material and motion of an object interact? Do we perceive the shape of an object differently when its surface material or the way it moves changes?
This paper is about dynamic mirror-like (specular) objects. Perceived 3D curvature magnitude for specular and matte-textured objects are very different from each other. The specular flow relies dominantly on the motion characteristics where the (matte) optic flow depends more on the 3D curvature information. In a 3D curvature magnitude discrimination task, we show that matte-textured objects are judged bumpier when rotating around vertical and horizontal axes as compared to flatter judgements when rotating around the viewing direction axis. Specular objects, on the other hand, prompt similar shape judgements regardless of the rotation axes. We conclude that the shape from specular flow is more invariant to changes in motion direction, where, shape judgements from optic flow (rotating matte-textured objects) are susceptible to rotation axis manipulation.
Dövencioğlu D.N., Ben-Shahar O., Barla, P., Doerschner K. (2017). Specular motion and 3D shape estimation. Journal of Vision. doi: 10.1167/17.6.3
How do we see the shape of an object if it is reflecting like a mirror? Does this object still appear to have the same shape when its reflectance changes to matte-textured?
Perceived shape in moving objects are affected by many aspects including surface reflectance. Here we use a novel, second-order shape probe to measure the local shape category of a rotating stimulus. We show that observers can estimate the local shape of moving objects with consistency and in correlation to the ground truth curvature of the 3D model. We also show that perceived local shape between moving specularly-reflecting and matte-textured objects are very different, significantly more than the surface reflectance differences in static objects. We conclude that the perception of local shape is modulated by surface material-specific optic flow.
Dövencioğlu D.N., Wijntjes M. W. A., Ben-Shahar O., Doerschner K. (2015). Effects of surface reflectance on local second order shape estimation in dynamic scenes. Vision Research. doi:10.1016/j.visres.2015.01.008