Rendering participating media is important for a number of domains, ranging from commercial applications (entertainment, virtual reality) to simulation systems (driving, flying and space simulators) and safety analyses (driving conditions, sign visibility). This article surveys global illumination algorithms for environments including participating media. It reviews both appearance-based and physically-based media methods, including the single scattering and the more general multiple-scattering techniques. The objective of the survey is the characterization of all these methods: Identification of their base techniques, assumptions, limitations and range of utilization. We conclude with some reflections about the suitability of the methods depending on the specific application involved, and possible future research lines.

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Loneliness is a common social phenomenon across countries with negative effects in health. Thus, the measurement of loneliness is of paramount importance. The Three-Item Loneliness Scale (TILS) was designed to be used in large-population surveys as a quick measure of loneliness. The aim of this study is to provide a Spanish validation of the TILS. A representative sample of the Spanish population (N = 1951) was used. We analysed the psychometric properties, factor structure, and distribution demographics characteristics of the Spanish TILS. Analyses showed differences regarding age, gender, educational level, employment status, household composition and annual gross income in line with previous literature. The confirmatory factor analysis revealed a unifactorial structure, with significant moderate correlations between the TILS and depression, anxiety, paranoia and wellbeing, and mild significant correlations with belongingness and mistrust. The internal consistency of the Spanish TILS was good (α = 0.82). Our study indicates that the TILS is a valid and reliable measure of loneliness in the Spanish population. Loneliness is a modern epidemic and a precursor of mental and health problems that reduced the quality of life. Therefore, it is important to have reliable measures of this phenomenon.

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