MatMix 1.0, a novel material probe for quantitatively measuring visual perception of materials

Recently Pont et al. (2012) showed that the appearance of objects consisting of any materials can be described as linear superpositions of objects of different canonical materials. In this study, we successfully implemented this method in a novel material probe (MatMix 1.0) to quantitatively measure visually perceived material qualities. The probe and stimuli were optical mixtures of four basis photos of a 3D object finished with four canonical types of materials (matte, velvety, specular, glittery). The probe images were taken under office lighting. A mixing desk type of interface was used in three matching experiments to quantify material perception. A stimulus image and the probe were shown together in the interface. Below the probe there were four sliders, representing the four materials, to control the probe appearance. In experiment 1, stimuli were lighted and viewed in the same way as the probe, whereas the 3D object was photographed from a different angle for experiment 2, and photographed under three canonical types of lighting (brilliant, diffuse, spot) for experiment 3. In each trial, observers were asked to match the material of the object in the probe with the material of the object in the stimulus. Experiment 1 showed surprisingly good results, indicating that participants handled the interface well. In experiment 2, the performance only slightly decreased and showed that observers truly matched perceived material qualities (not images). In addition, interactions between matte, velvety and specular components were found, while glittery was found to be relatively independent from all others. Experiment 3 confirmed the findings of the previous experiments, and showed that canonical lightings systematically affect material perception. Thus, MatMix 1.0 promisingly forms a robust and intuitive method to quantify visual material qualities. Results show that viewing and lighting conditions systematically influence material perception, suggesting that material consistency is not absolute.