Modeling Color Appearance in Augmented Reality

Augmented reality (AR) is a developing technology that is expected to become the next interface between humans and computers. One of the most common designs of AR devices is the optical see-through head- mounted display (HMD). In this design, the virtual content presented on the displays embedded inside the device gets optically superimposed on the real world which results in the virtual content being transparent. Color appearance in see-through designs of AR is a complicated subject, because it depends on many factors including the ambient light, the color appearance of the virtual content and color appearance of the real background. Similar to display technology, it is vital to control the color appearance of content for many applications of AR. In this research, color appearance in the see-through design of augmented reality environment is studied and modeled. Using a bench-top optical mixing apparatus as an AR simulator, objective measurements of mixed colors in AR were performed to study the light behavior in AR environment. Psychophysical color matching experiments were performed to understand color perception in AR. These experiments were performed first for simple 2D stimuli with single color both as background and foreground and later for more visually complex stimuli to better represent real content that is presented in AR. Color perception in AR environment was compared to color perception on a display which showed they are different from each other. The applicability of the CAM16 color appearance model, one of the most comprehensive current color appearance models, in AR environment was evaluated. The results showed that the CAM16 is not accurate in predicting the color appearance in AR environment. In order to model color appearance in AR environment, four approaches were developed using modifications in tristimulus and color appearance spaces, and the best performance was found to be for Approach 2 which was based on predicting the tristimulus values of the mixed content from the background and foreground color

Kamerankarakterisointijärjestelmän kalibrointi ja verifiointi

Miniature cameras are common in today's smartphones and other mobile devices. Achieving optimal image quality with such cameras requires elaborate characterization measurements done on the camera in laboratory conditions. The mobile phone company Nokia - and later Microsoft - has built an automated characterization system to perform these measurements. The quality of the characterization measurements done with this system depends on accurate calibration of the system. Calibration of this system has been tedious manual work, and the process has not been thoroughly documented. The goal of this research was to automate and improve the calibration process using the company's own software platform Mobile Imaging Playground (MIP). The measurement devices were integrated into MIP and all the calibration procedures were implemented as MIP plugins. A high quality spectroradiometer was used as a reference for the calibration. Multiple metrics were explored to evaluate the accuracy of the final system calibration and match to the reference. Uncertainties of the different calibration phases were also analyzed. For spectrally continuous and relatively smooth illuminants the calibration accuracy was high. Fluorescent spectra with narrow peaks were more problematic. Part of the problem can be attributed to the sparse sampling of the reference device, which causes the fluorescent peaks to be undersampled, so in reality the calibration results are most likely better than this. Keeping this in mind, reproduction of the fluorescent spectra after calibration can be considered at least colorimetrically accurate. The study proposed some future possibilities to improve the calibration process, for example by using a more suitable reference device and implementing some kind of bandpass correction.Pienoiskamerat ovat yleisiä nykypäivän älypuhelimissa ja muissa mobiililaitteissa. Parhaan mahdollisen kuvanlaadun saavuttaminen näillä kameroilla vaatii tarkkoja karakterisointimittauksia laboratorio-olosuhteissa. Matkapuhelimia valmistava yritys Nokia - ja myöhemmin Microsoft - on rakentanut automatisoidun kamerakarakterisointijärjestelmän näiden mittausten suorittamiseen. Karakterisointijärjestelmä tuottaa synteettisiä eri valonlähteiden spektrejä. Karakterisointimittausten laatu riippuu järjestelmän eri komponenttien kalibroinnin tarkkuudesta eli tarkkuudesta, jolla järjestelmä kykenee toistamaan ja mittaamaan halutun spektrin. Tämän tutkimuksen lähtökohtana olevan järjestelmän kalibrointi on ollut hidasta käsityötä, ja prosessia ei ole dokumentoitu kovin tarkasti. Tutkimuksen tavoite oli automatisoida ja parantaa kalibrointiprosessia yrityksen omaa ohjelmistoalustaa Mobile Imaging Playgroundia (MIP) käyttäen. Korkealaatuista spektroradiometriä käytettiin referenssilaitteena kalibrointityössä. Lopullisen kalibrointilaadun arvioimiseksi käytettiin useita aiempien tutkimusten perusteella määritettyjä mittoja. Kalibrointivaiheiden epävarmuustekijöiden vaikutuksia ja suuruutta tutkittiin myös. Spektraalisesti jatkuvien ja verrattain tasaisten valonlähteiden kohdalla lopullisen kalibroinnin tarkkuus osoittautui erittäin hyväksi. Loisteputkivalonlähteet, joiden spektri on piikikäs, toistuivat kalibroinnin jälkeen huonommin kuin jatkuvaspektriset valonlähteet. Tämä johtui luultavasti referenssilaitteen harvasta näytteistyksestä, joka aiheuttaa terävien spektripiikkien alinäytteistymistä. Todellisuudessa loisteputkivalonlähteiden kalibroinnin laatu on siis luultavasti parempi kuin tulokset antavat ymmärtää, ja kalibrointia voidaan pitää kolorimetrisesti tarkkana. Työssä esitetään myös tulevaisuutta silmällä pitäen muutamia parannusehdotuksia kalibrointiprosessiin, kuten paremman referenssilaitteen valinta ja jonkinlaisen kaistanpäästökorjauksen toteutus

Programmable Image-Based Light Capture for Previsualization

Previsualization is a class of techniques for creating approximate previews of a movie sequence in order to visualize a scene prior to shooting it on the set. Often these techniques are used to convey the artistic direction of the story in terms of cinematic elements, such as camera movement, angle, lighting, dialogue, and character motion. Essentially, a movie director uses previsualization (previs) to convey movie visuals as he sees them in his minds-eye . Traditional methods for previs include hand-drawn sketches, Storyboards, scaled models, and photographs, which are created by artists to convey how a scene or character might look or move. A recent trend has been to use 3D graphics applications such as video game engines to perform previs, which is called 3D previs. This type of previs is generally used prior to shooting a scene in order to choreograph camera or character movements. To visualize a scene while being recorded on-set, directors and cinematographers use a technique called On-set previs, which provides a real-time view with little to no processing. Other types of previs, such as Technical previs, emphasize accurately capturing scene properties but lack any interactive manipulation and are usually employed by visual effects crews and not for cinematographers or directors. This dissertation\u27s focus is on creating a new method for interactive visualization that will automatically capture the on-set lighting and provide interactive manipulation of cinematic elements to facilitate the movie maker\u27s artistic expression, validate cinematic choices, and provide guidance to production crews. Our method will overcome the drawbacks of the all previous previs methods by combining photorealistic rendering with accurately captured scene details, which is interactively displayed on a mobile capture and rendering platform. This dissertation describes a new hardware and software previs framework that enables interactive visualization of on-set post-production elements. A three-tiered framework, which is the main contribution of this dissertation is; 1) a novel programmable camera architecture that provides programmability to low-level features and a visual programming interface, 2) new algorithms that analyzes and decomposes the scene photometrically, and 3) a previs interface that leverages the previous to perform interactive rendering and manipulation of the photometric and computer generated elements. For this dissertation we implemented a programmable camera with a novel visual programming interface. We developed the photometric theory and implementation of our novel relighting technique called Symmetric lighting, which can be used to relight a scene with multiple illuminants with respect to color, intensity and location on our programmable camera. We analyzed the performance of Symmetric lighting on synthetic and real scenes to evaluate the benefits and limitations with respect to the reflectance composition of the scene and the number and color of lights within the scene. We found that, since our method is based on a Lambertian reflectance assumption, our method works well under this assumption but that scenes with high amounts of specular reflections can have higher errors in terms of relighting accuracy and additional steps are required to mitigate this limitation. Also, scenes which contain lights whose colors are a too similar can lead to degenerate cases in terms of relighting. Despite these limitations, an important contribution of our work is that Symmetric lighting can also be leveraged as a solution for performing multi-illuminant white balancing and light color estimation within a scene with multiple illuminants without limits on the color range or number of lights. We compared our method to other white balance methods and show that our method is superior when at least one of the light colors is known a priori

Calm Displays and Their Applications : Making Emissive Displays Mimic Reflective Surfaces Using Visual Psychophysics, Light Sensing and Colour Science

Ph. D. Thesis.Our environment is increasingly full of obtrusive display panels, which become illuminating surfaces when on, and void black rectangles when off. Some researchers argue that emissive displays are incompatible with Weiser and Seely Brown's vision of "calm technology", due to their inability to seamlessly blend into the background. Indeed, Mankoff has shown that for any ambient technology, the ability to move into the periphery is the most relevant factor in their usability. In this thesis, a background mode for displays is proposed based on the idea that displays can look like an ordinary piece of reflective paper showing the same content. The thesis consists of three main parts. In the first part (Chapter 4), human colour matching performance between an emissive display and reflective paper under chromatic lighting conditions is measured in a psychophysical experiment. We find that threshold discrimination ellipses vary with condition (16.0×6.0 ΔEab on average), with lower sensitivity to chroma than hue changes. Match distributions are bimodal for some conditions. In the second part (Chapter 5), an algorithm enabling emissive displays to look like reflective paper is described and evaluated, giving an average error of ΔEab = 10.2 between display and paper. A field study showed that paper-like displays are more acceptable in bedrooms and that people are more likely to keep them always on than normal displays. Finally, the third part (Chapter 6) concerns the development and four-week trial of a paper-like display application. Using the autobiographical design method, a system for sharing bedtime with a remote partner was developed. We see that once unobtrusive, display systems are desired for use even in spaces like bedrooms. Paper-like displays enable both emerging and existing devices to move into the periphery and become “invisible”, and therefore provide a new building block of calm technology that is not achievable using simple emissive displays

Rumney, New Hampshire annual report of the town officers for the fiscal year ending December 31, 2007, 2008 town meeting.

This is an annual report containing vital statistics for a town/city in the state of New Hampshire