Abstract
Visual perception of shape from texture has lead to numerous studies to unravel which cues are effectively used by observers. Recently, Li and Zaidi (2004 Journal of Vision 4 860–878) have suggested distinguishing between frequency and orientation cues. Following this distinction, we evaluate the contribution of frequency gradients and orientation flow for the perception of shape from texture. We present several experiments based on purposely-designed stimuli. Each stimulus represents a cylinder covered by a homogenous texture composed of Gabor patches. The cylinder is presented upright with different radius and is viewed under perspective projection. Importantly, the frequency of each Gabor patch is determined by the local spatial frequency gradient defined by the projection. Similarly, the orientation is determined by the local vanishing point induced by the orientation flow along the direction of the patch. Thus, we are able to independently manipulate the frequency and the orientation gradients in order to obtain a texture with a specific combination of cues. We synthesize textures presenting only a frequency gradient or an orientation gradient or both gradients. For each texture, a shape discrimination task and an absolute shape judgment task are performed. We find that orientation-defined textures are better discriminated than frequency-defined textures. In addition, a perturbation analysis reveals that orientation flow dominated over frequency gradient. These results validate our stimuli to study the perception of shape from texture and the decomposition of the texture cue into elementary components.