Appearance

In the regime of color science, I’m mostly  interested in visual appearance measuring and modeling. Visual appearance usually includes scene and object appearance. The complexity of appearance makes it almost impossible to quantitatively analyze appearance as a whole. The solution to appearance modeling is to decompose it into different scenario. Appearance modeling serves as a useful tool for understanding human visual system, which is an “imaging” system that processes information in a peculiar yet efficient way. Aligning modern instruments toward human perception such that “what we measure is what we see” is an ultimate goal in this research area.

surface appearance
  • gloss

Recent advances in Bidirectional Reflectance Distribution Functions (BRDF) acquisition have provided a novel approach for appearance measurement and analysis. In particular, since gloss appearance is dependent on the directional reflective properties of surfaces, it is reasonable to leverage BRDF for gloss evaluation. In this project, we investigate gloss appearance from both soft metrology and hard metrology. A psychophysical experiment was conducted for gloss assessment on 47 neutral-color samples. In the evaluation of gloss perception from gloss meter measurements, we report several ambiguous correspondences in the medium gloss range. In order to analyze and explain this phenomenon, BRDF was acquired and examined using a commercial BRDF measuring device. With an improved correlation to visual perception, we propose a two-dimensional gloss model by combining a parameter, the standard deviation of specular lobe from Ward’s BRDF model with measured gloss values.

LS: halogen light source; SUT: sample under test; DH: diffuse hemisphere; CM: convex mirror.

Diffuse coarseness (graininess) and glint impression (sparkle) are two aspects of visual perception for special-effect materials, including car finishes, etc. In this work, three psychophysical experiments were carried out, including diffuse coarseness assessment, glint impression assessment, and finding dimensions of glint space. In the experiments, one geometry for diffuse coarseness and three geometries for glint impression were designed. A further investigation on glint space was conducted using the multidimensional scaling technique. From the visual results, two dimensions, corresponding to two attributes, were extracted and were validated by the instrumental results. 

scene appearance
  • color correlated temperature (CCT) of indoor scenes

One aspect of visual appearance is scene appearance. This project seeks to render indoor scenes at different color temperatures.