Materials: Between perception and reality Humans and machines 'perceive' materials differently. An EU-funded project studied people's perceptions of materials in order to improve electronic descriptors. Industrial Technologies © Thinkstock Human perception is subjective and can differ quite significantly between individuals. With this in mind, the EU-funded 'Perceptual analysis and simulation of real-world materials appearance' (PASIMA) strove to shed light on how people perceive various materials. Given the complexity of materials, the project — funded by the EU's Seventh Framework Programme (FP7) — focused on the textural representation of the surface, its illumination and view-dependent effects. To study these, PASIMA analysed the materials using bi-directional reflectance distribution function (BRDF) and bi-directional texture function (BTF). The project studied how the perception of material appearance relates to mathematical features. PASIMA conducted psycho-physical experiments to investigate visual perceptions of a wide spectrum of smooth materials appearances, as well as how humans reacted to realistic renderings of planar material patches. Project members also compared the performance of human subjects with that of several standard textural descriptors. Moreover, PASIMA investigated human perceptual sensitivity to different levels of environmental illumination of realistic stimuli represented by several BTF datasets. In its second phase, the project formulated acquisition and processing techniques to deal with complex illumination and view-dependent BRDF and BTF datasets. This included a novel registration method that compensates for materials and registration plane misalignment to correct the inaccuracy of standard BTF approaches. PASIMA results should lead to the emergence of more accurate BTF and BRDF techniques that also require less storage space and processing capacity. This will take materials description technology out of the lab and into the hands of general professionals too.