Hyperspectral Modeling of Material Appearance: General Framework, Challenges and Prospects

The main purpose of this tutorial is to address theoretical and practical issues involved in the development of predictive material appearancemodels for interdisciplinary applications within and outside the visible spectral domain. We examine the specific constraints and pitfalls found in each of the key stages of the model development framework, namely data collection, design and evaluation, and discuss alternatives to enhance the effectiveness of the entire process. Although predictive material appearance models developed by computer graphics researchers are usually aimed at realistic image synthesis applications, they also provide valuable support for a myriad of advanced investigations in related areas, such as computer vision, image processing and pattern recognition, which rely on the accurate analysis and interpretation of material appearance attributes in the hyperspectral domain. In fact, their scope of contributions goes beyond the realm of traditional computer science applications. For example, predictive light transport simulations, which are essential for the development of these models, are also regularly beingused by physical and life science researchers to understand andpredict material appearance changes prompted by mechanisms which cannot be fully studied using standard ``wet'' experimental procedures.For completeness, this tutorial also provides an overview of such synergistic research efforts and in silico investigations, which are illustrated by case studies involving the use of hyperspectral material appearance models

Mapping And Monitoring Wetland Environment By Analysis Different Satellite Images And Field Spectroscopy

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2010Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2010Bu çalışmada farklı spektral ve mekansal çözünürlükte uydu görüntülerinin “Terkos Havzası Sulak Alanı” örneğinde; arazi örtüsünde meydana gelen değişimleri ve sulak alan bitki türlerinin belirlenmesinde kullanılabilirlikleri için uygulanabilecek uzaktan algılama yöntemleri ele alınmıştır. Kullanılan yöntemler ile elde edilen yeni işlenmiş görüntülerin performanslarının yersel yansıtım değerleri kullanılarak desteklenmesi ile doğal alanların sürdürülebilir korunma ve yönetimi için uzaktan algılama verilerine dayalı bir altlık rehberin oluşturulması imkanı araştırılmıştır. Elde edilen sonuçlara göre heterojen arazi örtüsü yapısına sahip olan çalışma bölgesinde değişim tespiti için Ana Bileşen Dönüşümüne dayalı değişim tespit yöntemi en iyi sonucu vermiştir. Ayrıca bu çalışmada, hiperspektral Hyperion EO-1 görüntüsü ile sulak alan bitki örtüsünün diğer bitki türlerinden doğru olarak ayırt edilebildiği ortaya konmuştur. Sulak alan bitki türlerinin kendi içinde ayırt edilebilmesi ancak yersel spektroskopi ile mümkün olduğu sonucuna ulaşılmıştır.In this study, different satellite data that has different spectral and spatial resolution and in-situ spectroradiometer measurements were used to analyze hydrophytic vegetation and surrounded land cover for sustainable development and conservation of Terkos wetlands. By supporting performances of processed images with field collected reflectance values, the feasibility of structuring a basic guide based on remote sensing data for sustainable preservation and management of natural lands was searched. According to result, land cover changes in the complex natural area were determined more accurately by using PCA based change detection method Therefore, the performance of spaceborne Hyperion EO-1 hyperspectral data was analyzed to determine the capability of the data for wetland vegetation discrimination than the other vegetated areas. At the last stage of the study, field collected reflectance values that have different wetland flora types were compared by statistical ANOVA method and reflectance differences between vegetation types were put forward through calculations.DoktoraPh

On the Modelling of Hyperspectral Light and Skin Interactions and the Simulation of Skin Appearance Changes Due to Tanning

The distinctive visual attributes of human skin are largely determined by its interactions with light across different spectral domains. Accordingly, the modelling of these interactions has been the object of extensive investigations in numerous fields for a diverse range of applications. However, only a relatively small portion of these research efforts has been directed toward the comprehensive simulation of hyperspectral light and skin interactions, as well as the associated temporal changes in skin appearance, which can be caused by a myriad of time-dependent photobiological phenomena. In this thesis, we explore this area of research. Initially, we present the first hyperspectral model designed for the predictive rendering of skin appearance attributes in the ultraviolet, visible and infrared domains. We then describe a novel physiologically-based framework for the simulation and visualization of skin tanning dynamics, arguably the most prominent and persistent of such relevant time-dependent phenomena. The proposed model incorporates the intrinsic bio-optical properties of human skin affecting hyperspectral light transport, including the particle nature and distribution patterns of the main light attenuation agents found within the cutaneous tissues. Accordingly, it accounts for phenomena that significantly affect skin spectral signatures within and outside the visible domain, such as detour and sieve effects, which are overlooked by existing skin appearance models. Using a first principles approach, this model computes the surface and subsurface scattering components of skin reflectance taking into account not only the wavelength and the illumination geometry, but also the positional dependence of the reflected light. Hence, the spectral and spatial distributions of light interacting with human skin can be comprehensively represented in terms of hyperspectral reflectance and scattering distribution functions respectively. The proposed tanning simulation framework incorporates algorithms that explicitly account for the connections between spectrally-dependent light stimuli and time-dependent physiological changes occurring within the cutaneous tissues. For example, it utilizes the above hyperspectral model as a modular component to evaluate the wavelength-dependence of the tanning phenomenon. This enables the effective simulation of the skin's main adaptive mechanisms to ultraviolet radiation as well as its responses to distinct light exposure regimes. We demonstrate the predictive capabilities of this framework through quantitative and qualitative comparisons of simulated data with measurements and experimental observations reported in the scientific literature. We also provide image sequences depicting skin appearance changes elicited by time-dependent variations in skin biophysical parameters. The work presented in this thesis is expected to contribute to advances in realistic image synthesis by increasing the spectral and temporal domains of material appearance modelling, and to provide a testbed for interdisciplinary investigations involving the visualization of skin responses to photoinduced processes

On the Modelling of Hyperspectral Light and Skin Interactions and the Simulation of Skin Appearance Changes Due to Tanning

The distinctive visual attributes of human skin are largely determined by its interactions with light across different spectral domains. Accordingly, the modelling of these interactions has been the object of extensive investigations in numerous fields for a diverse range of applications. However, only a relatively small portion of these research efforts has been directed toward the comprehensive simulation of hyperspectral light and skin interactions, as well as the associated temporal changes in skin appearance, which can be caused by a myriad of time-dependent photobiological phenomena. In this thesis, we explore this area of research. Initially, we present the first hyperspectral model designed for the predictive rendering of skin appearance attributes in the ultraviolet, visible and infrared domains. We then describe a novel physiologically-based framework for the simulation and visualization of skin tanning dynamics, arguably the most prominent and persistent of such relevant time-dependent phenomena. The proposed model incorporates the intrinsic bio-optical properties of human skin affecting hyperspectral light transport, including the particle nature and distribution patterns of the main light attenuation agents found within the cutaneous tissues. Accordingly, it accounts for phenomena that significantly affect skin spectral signatures within and outside the visible domain, such as detour and sieve effects, which are overlooked by existing skin appearance models. Using a first principles approach, this model computes the surface and subsurface scattering components of skin reflectance taking into account not only the wavelength and the illumination geometry, but also the positional dependence of the reflected light. Hence, the spectral and spatial distributions of light interacting with human skin can be comprehensively represented in terms of hyperspectral reflectance and scattering distribution functions respectively. The proposed tanning simulation framework incorporates algorithms that explicitly account for the connections between spectrally-dependent light stimuli and time-dependent physiological changes occurring within the cutaneous tissues. For example, it utilizes the above hyperspectral model as a modular component to evaluate the wavelength-dependence of the tanning phenomenon. This enables the effective simulation of the skin's main adaptive mechanisms to ultraviolet radiation as well as its responses to distinct light exposure regimes. We demonstrate the predictive capabilities of this framework through quantitative and qualitative comparisons of simulated data with measurements and experimental observations reported in the scientific literature. We also provide image sequences depicting skin appearance changes elicited by time-dependent variations in skin biophysical parameters. The work presented in this thesis is expected to contribute to advances in realistic image synthesis by increasing the spectral and temporal domains of material appearance modelling, and to provide a testbed for interdisciplinary investigations involving the visualization of skin responses to photoinduced processes