Understanding the role of phase function in translucent appearance

Multiple scattering contributes critically to the characteristic translucent appearance of food, liquids, skin, and crystals; but little is known about how it is perceived by human observers. This article explores the perception of translucency by studying the image effects of variations in one factor of multiple scattering: the phase function. We consider an expanded space of phase functions created by linear combinations of Henyey-Greenstein and von Mises-Fisher lobes, and we study this physical parameter space using computational data analysis and psychophysics. Our study identifies a two-dimensional embedding of the physical scattering parameters in a perceptually meaningful appearance space. Through our analysis of this space, we find uniform parameterizations of its two axes by analytical expressions of moments of the phase function, and provide an intuitive characterization of the visual effects that can be achieved at different parts of it. We show that our expansion of the space of phase functions enlarges the range of achievable translucent appearance compared to traditional single-parameter phase function models. Our findings highlight the important role phase function can have in controlling translucent appearance, and provide tools for manipulating its effect in material design applications.National Institutes of Health (U.S.) (Award R01-EY019262-02)National Institutes of Health (U.S.) (Award R21-EY019741-02

APGV '04: 1st Symposium on Applied Perception in Graphics and Visualization

Three years ago, when a small group of us gathered in Snowbird for a "campfire" on Graphics and Perception, there was a certain air of excitement that things were getting started. Last year .s record turnout at the Graphics and Perception Birds of a Feather meeting at SIGGRAPH confirmed the growing interest in this area, and the realization that perception is playing an increasingly important role in graphics and visualization. Soon after the BOF, at the SIGGRAPH .03 reception, we learned of the opportunity to hold a symposium on applied perception co-located with SIGGRAPH .04. A year to get organized is not a very long time in this busy world we live in. We scrambled to try to bring together everyone we thought would like to be involved, and even managed an impromptu meeting outside the conference center. Many phone calls and emails later, and our committee began to emerge. We are extremely grateful to everyone who helped make this a reality.Our goal for this symposium is to have it serve as an inclusive forum where researchers working at the intersection of perception, graphics and visualization can come together to share ideas and results. We hope to provide a great opportunity for people not only to acquire new knowledge, but also to seek new partnerships and collaborations. Working together can only help us all.We are pleased to present the Proceedings of the First Symposium on Applied Perception in Graphics and Visualization (APGV .04). We received 38 paper submissions in response to the call for participation. Manuscripts were received from both the perception and from the graphics research communities. Several teams of authors represented active interdisciplin-ary efforts. A wide range of topics were treated . including color, shape, motion, distance judgments, virtual reality, and haptics, as well as application areas such as product design and medicine. Each paper received three to four reviews by members of the international program committee. We originally planned a somewhat smaller program, but the overall qual-ity of the submitted work was very high. In the end we made some difficult choices and accepted 21 of the papers.We also issued a call for posters, and received numerous submissions treating diverse problems. Included here are the abstracts of the posters accepted for the Symposium

Geometric Analysis in Cultural Heritage

We present a review of recent techniques for performing geometric analysis in cultural heritage applications, targeting the broad community of researchers and practitioners in cultural heritage computing. The problems considered include shape perception enhancement, restoration and preservation support, monitoring over time, object interpretation, and collection analysis. All of these problems typically rely on an understanding of the structure of the shapes in question at both a local and global level. In this survey, we discuss the different problem forms and review the main solution methods, aided by classification criteria based on the geometric scale at which the analysis is performed and the cardinality of the relationships among object parts exploited during the analysis. We finalize the report by discussing open problems and future perspectives

A visibility matching tone reproduction operator for high dynamic range scenes

The authors present a tone reproduction operator that preserves visibility in high dynamic range scenes. The method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. They compare the results to previous work and present examples the techniques applied to lighting simulation and electronic photography