Vision is a component of a perceptual system whose function is to support purposeful behavior. In this project we studied the perceptual system that supports the visual perception of surface properties through manipulation. Observers were tasked with finding dents in simulated flat glossy surfaces. The surfaces were presented on a tangible display system implemented on an Apple iPad, that rendered the surfaces in real time and allowed observers to directly interact with them by tilting and rotating the device. On each trial we recorded the angular deviations indicated by the device's accelerometer and the images seen by the observer. The data reveal purposeful patterns of manipulation that serve the task by producing images that highlight the dent features. These investigations suggest the presence of an active visuo-motor perceptual system involved in the perception of surface properties, and provide a novel method for its study using tangible display systems
Perlin noise, a type of procedural noise, was used for the design of elevation files for 2.5D printing. This printing method uses elevation data from a height map to create physical relief by superimposing layers of ink. In this experiment, the grayscale values of noise functions were used as elevation values to build different surface structures in UV curable ink by 2.5D printing. Printed samples with varying levels of Perlin noise were created and their reflectance properties were studied by measuring the values of specular gloss. The roughness and specular gloss of the printed surfaces were effectively influenced when varying the persistence and octaves of the noise functions. The aim of implementing the procedural approach to a high-resolution printing method has been to explore the reflectance properties of custom noise functions when transferred to the physical realm. This might contribute to better understand the effect of surface structure on the appearance of materials. Potentially, this approach will enable the use of relief printing to produce structures with a more natural appearance and a desired gloss value by using a low-cost computing process.