Effects of different texture cues on curved surfaces viewed stereoscopically

Stereoscopic shape judgements can be modified by the addition of texture cues. This paper examines the properties of texture that are responsible for this effect. When a three-dimensional curved surface is projected onto a two-dimensional image, changes in surface orientation result in gradients of texture element size (or area), shape (compression) and density in the image. Manipulating each of these gradients independently we found that 97% of the variance in the results could be accounted for by the compression gradient. When the texture pattern corresponds to a highly anisotropic texture on the object's surface, shape-from-texture becomes ineffective. These results suggest that human shape-from-texture proceeds under the assumption that textures are statistically isotropic, and not that they are homogeneous.