Textures are used widely in computer graphics to represent fine visual details and produce realistic looking images. Often it is necessary to remove some foreground object from the scene. Removal of the portion creates one or more holes in the texture image. These holes need to be filled to complete the image. Various methods like clone brush strokes and compositing processes are used to carry out this completion. User skill is required in such methods. Texture synthesis can also be used to complete regions where the texture is stationary or structured. Reconstructing methods can be used to fill in large-scale missing regions by interpolation. Inpainting is suitable for relatively small, smooth and non-textured regions. A number of other approaches focus on the edge and contour completion aspect of the problem. In this thesis we present a novel approach for addressing this image completion problem. Our approach focuses on image based completion, with no knowledge of the underlying scene. In natural images there is a strong horizontal orientation of texture/color distribution. We exploit this fact in our proposed algorithm to fill in missing regions from natural images. We follow the principle of figural familiarity and use the image as our training set to complete the image.

Photo editing software allows digital images to be blurred, warped or re-colored at the touch of a button. However, it is not currently possible to change the material appearance of an object except by painstakingly painting over the appropriate pixels. Here we present a set of methods for automatically replacing one material with another, completely different material, starting with only a single high dynamic range image, and an alpha matte specifying the object. Our approach exploits the fact that human vision is surprisingly tolerant of certain (sometimes enormous) physical inaccuracies. Thus, it may be possible to produce a visually compelling illusion of material transformations, without fully reconstructing the lighting or geometry. We employ a range of algorithms depending on the target material. First, an approximate depth map is derived from the image intensities using bilateral filters. The resulting surface normals are then used to map data onto the surface of the object to specify its material appearance. To create transparent or translucent materials, the mapped data are derived from the object's background. To create textured materials, the mapped data are a texture map. The surface normals can also be used to apply arbitrary bidirectional reflectance distribution functions to the surface, allowing us to simulate a wide range of materials. To facilitate the process of material editing, we generate the HDR image with a novel algorithm, that is robust against noise in individual exposures. This ensures that any noise, which would possibly have affected the shape recovery of the objects adversely, will be removed. We also present an algorithm to automatically generate alpha mattes. This algorithm requires as input two images--one where the object is in focus, and one where the background is in focus--and then automatically produces an approximate matte, indicating which pixels belong to the object. The result is then improved by a second algorithm to generate an accurate alpha matte, which can be given as input to our material editing techniques.

In the computer graphics production environment, artists often must tweak specific lighting and material parameters to match a mind's eye vision of the appearance of a 3D scene. However, the interaction between a material and a lighting environment is often too complex to cognitively predict without visualization. Therefore, artists operate in a design cycle, where they tweak the parameters, wait for a visualization, and repeat, seeking to obtain a desired look. We propose the use of appearance-driven material design. Here, artists directly design the appearance of reflected light for a specific view, surface point, and time. In this thesis, we discuss several methods for appearance-driven design with homogeneous materials, spatially-varying materials, and appearance-matching materials, where each uses a unique modeling and optimization paradigm. Moreover, we present a novel treatment of the illumination integral using sampling theory that can utilize the computational power of the graphics processing unit (GPU) to provide real-time visualization of the appearance of various materials illuminated by complex environment lighting. As a system, the modeling, optimization and rendering steps all operate on arbitrary geometry and in detailed lighting environments, while still providing instant feedback to the designer. Thus, our approach allows materials to play an active role in the process of set design and story-telling, a capability that was, until now, difficult to achieve due to the unavailability of interactive tools appropriate for artists.

Rendering of natural scenes has interested the scientific community for a long time due to its numerous applications. The targeted goal is to create images that are similar to what a viewer can see in real life with his/her eyes. The main obstacle is complexity: nature scenes from real life contain a huge number of small details that are hard to model, take a lot of time to render and require a huge amount of memory unavailable in current computers. This complexity mainly comes from geometry and lighting. The goal of our research is to overcome this complexity and to achieve real-time rendering of nature scenes while providing visually convincing dynamic global illumination. Our work focuses on grass and trees as they are commonly visible in everyday life. We handle geometry and lighting complexities for grass to render millions of grass blades interactively with dynamic lighting. As for lighting complexity, we address real-time rendering of trees by proposing a lighting model that handles indirect lighting. Our work makes extensive use of the current generation of Graphics Processing Units (GPUs) to meet the real-time requirement and to leave the CPU free to carry out other tasks.

This thesis documents my process as Scenic Designer for Richard O'Brien's musical, The Rocky Horror Show, presented by the University of Central Florida Conservatory Theatre. This production premiered on the University of Central Florida's Mainstage Theatre 29 March 2007 and ran for fifteen performances, closing on 15 April 2007. This thesis includes my research and analysis of the published script and a production journal which documents my process for our specific production. In this document, I illustrate how my communication and meetings with the director and members of the design team moved from initial conversations into the research, development, and construction processes in order to create the realized production. I explain the challenges and obstacles I faced in the development and construction stages and how my communication with members of the design and production staff led to the final design. Throughout this document, I present figures displaying the preliminary sketches, renderings, construction process, and production photographs that illustrate how the production moved from an idea to a reality. I also present a self analysis of the process and final product through personal reflection and outside response.

The interaction of light in our world is immensely complex, but with mod- ern computers and advanced rendering algorithms, we are beginning to reach the point where photo-realistic renders are truly difficult to separate from real photographs. Achieving realistic or believable global illumination in scenes with participating media is exponentially more expensive compared to our traditional polygonal methods. Light interacts with the particles of a volume, creating com- plex radiance patterns. In this thesis, we introduce an extension to the commonly used point-based color bleeding (PCB) technique, implementing volume scatter contributions. With the addition of this PCB algorithm extension, we are able to render fast, be- lievable in- and out-scattering while building on existing data structures and paradigms. The proposed method achieves results comparable to that of existing Monte Carlo integration methods, obtaining render speeds between 10 and 36 times faster while keeping memory overhead under 5%.

Modeling believable lighting is a crucial component of computer graphics applications, including games and modeling programs. Physically accurate lighting is complex and is not currently feasible to compute in real-time situations. Therefore, much research is focused on investigating efficient ways to approximate light behavior within these real-time constraints. In this thesis, we implement a general purpose algorithm for real-time applications to approximate indirect lighting. Based on voxel cone tracing, we use a filtered representation of a scene to efficiently sample ambient light at each point in the scene. We present an approach to scene voxelization using hardware tessellation and compare it with an approach utilizing hardware rasterization. We also investigate possible methods of warped voxelization. Our contributions include a complete and open-source implementation of voxel cone tracing along with both voxelization algorithms. We find similar performance and quality with both voxelization algorithms.

Background. The game-industry is rapidly demanding more and more comput-ing power in its strive for more realistic renditions of environments, simulations andgraphics. To accelerate the improvements made to the realism of real time graph-ics further, optimizations like Clustered and Cascaded Clustered Shading come intoplay. The purpose of these techniques is to reduce the time it takes to render aframe by dividing the view frustum into smaller segments called clusters that canthen be used for light calculations. Cascaded Clustered Shading is a slightly morecustomizable method which aims to improve on Clustered Shading by allowing morecontrol over how the view frustum is divided into clusters. Objectives. The goal of our thesis is to explore the effectiveness of Cascaded Clus-tered Shading compared to Clustered Shading in a scene with 64, 256, 1024 and 4096lights respectively. It is also to find the trend of what type of subdivision pattern thatperforms best in what situation. Thus proving or disproving the theory that moreuniform cluster sizes are beneficial in reducing the complexity of light calculations incomparison to the increasing cluster sizes present in Clustered Shading. Methods. To answer these questions we implemented the techniques in a test scenewhere we could easily compare the performance of the different subdivision patternsand techniques with 64, 256, 1024 and 4096 lights respectively. Three different pat-terns were tested, one with an increasing number of subdivisions per layer P1 (anincrease in the number of clusters per layer). One with a static number of subdi-visions per layer P2, representing the performance of Clustered Shading. One witha decreasing number of subdivisions per layer P3. Additional performance metricsto be recorded were added, measuring the time it took for the different parts of thetechnique so that not just the general performance could be compared. Thus themethod used was a quantitative research method of implementation and experimen-tation. Results. The results supports the theory that more uniform cluster sizes tend tobe beneficial when rendering a scene with many lights showing a clear trend to favora pattern creating more uniform clusters P1. However the results also show a con-tradicting overall performance increase (comparing FPS) using the reversed patternwith sharply increasing cluster sizes based on the distance from the camera P3. Theoverall performance of pattern P1 and P3 was better than P2. Conclusions. The conclusions drawn from the results are that Cascaded ClusteredShading perform better than Clustered Shading in most cases depending on the pat-tern, and that more uniform cluster sizes are beneficial when rendering many lightsin most cases.

The digital reproduction of materials has developed greatly over the past decades. The improved interactive rendering technology available nowadays enables broad digital visualization applications like gaming, cinema and film production, advertising, and online shopping. These recent advances in digital technologies are also playing an important role in the improvement of some industrial processes such as computer-aided design and manufacturing, virtual prototyping, and scientific visualization and simulation. Currently, many rendering software packages provide impressive images and often even claim photorealism. However, producing realistic appearance images is very challenging taking into account the high sensitivity of the human visual system. The visual appearance of products is still an important aspect to take into account even for the digital simulation of materials, since the appearance of these simulated products on the screen is still a critical parameter in the purchase decision of customers. During the last years different efforts have been carried out by industrial manufacturers in different applications, such as textile, cosmetic, automotive, etc., to provide attractive visual effects and new visual impressions of their products using, for instance, innovative effect pigments, also called goniochromatic pigments. The digital rendering of these pigments is a very active hot topic since this type of coatings changes considerably its visual attributes such as color and texture with the illumination/viewing geometry. Achieving accurate simulation of these materials demands an extra effort due to the physical complexity of their surfaces. Special BRDFs (bidirectional reflectance distribution functions) reflectance models are needed to characterize their visual appearance. This complex appearance is produced due to the presence of special effect pigments containing metallic, interference, or pearlescent pigments, which are responsible for the strong dependence of the color of these coatings on viewing and illumination directions. These pigments also exhibit visually complex texture effects such as sparkle and graininess. Under bright direct illumination conditions, such as sunlight, the flakes create a sparkling effect, while under diffuse illumination such as a cloudy sky, effect coatings create a salt and pepper appearance or a light/dark irregular pattern, which is usually referred to as graininess or coarseness. Two main issues limit the digital reproduction of effect pigments. The first issue is related to the current display technologies. The quality of the displays is an essential component toward accurate color reproduction of materials. Previous studies have evaluated the validity of available display technologies for the visualization and digital reproduction of effect pigments, which are usually not enough for the reproduction of such a wide variety of colors due to their limited color gamut. The second limitation is more related to the current rendering software. The color accuracy of their images is often not sufficient for the reproduction of colors and effects produced by these materials. The available rendering software provides impressive images that serve the needs for applications such as the cinema and games industries, but when it comes to more critical applications such as automotive design, the color accuracy of their rendered images is not accurate enough, especially for such complex materials such as effect pigments. The first issue is addressed in this thesis by, evaluating the performance of the new Quantum dots (QDs) display technology for the reproduction of effect pigments. For further improving the display capability, a new solution is given by developing a multi-primary display model based on the QDs technology (addressed in the first research article of this thesis in chapter 1). The proposed multi-primary display model provides an expanded color gamut, which guarantees a better reproduction of effect pigments. In a first step, the emission spectral radiance curves of the three RGB channels of a commercial QD display were fitted to a four-parameter function. From this modeling, it is possible to gain new theoretical color primaries by selecting new spectral peaks (cyan, yellow, magenta, and/or additional RGB primaries) and imposing colorimetric conditions for the resulting white of this proposed theoretical multi-primary display. Proper characterization to assess the performance of the display was conducted to know if the basic “gain-offset-gamma” (GOG) model can be used for direct and inverse color reproduction (from RGB to CIE-XYZ, and vice versa). The GOG model was found to well characterize this display. The spatial uniformity of the display was also evaluated in luminance and color chromaticity terms. Finally, with the primaries modeling and color characterization based on the GOG model, a 5-primary model (RGBYC) was tested. The evaluation of this theoretical RGBYC display model confirms the gamut enlargement, which can also improve goniochromatic color reproduction. In the second place, and focusing on the second issue, a big portion of the work of this thesis was dedicated to the development of a new 3D rendering tool for improved and accurate visualization of the complete appearance of effect coatings, including metallic effects, sparkle, and iridescence (addressed in the second and third research articles of this thesis in chapters 2 and 3). This task was carried on by firstly building a specific rendering framework for this purpose, using a multi-spectral and physically based rendering approach, and secondly, by validating the performance of this rendering framework through psychophysical tests. Spectral reflectance measurements and sparkle indices from a commercially available multi-angle spectrophotometer (BYK-mac i) were used together with a physically based approach, such as flake-based reflectance models, to efficiently implement the appearance reproduction from a small number of bidirectional measurement geometries. With this rendering framework, a virtual representation of a set of effect coating samples is reproduced on an iPad display, by simulating how these samples would be viewed inside a Byko-spectra effect light booth. Therefore, for this purpose, an accurate virtual representation of the Byko light booth was built using a physically based representation of global illumination. The rendering framework also accounts for the colorimetric specifications of the rendering display (iPad5) by applying the recent device-specific MDCIM model. The appearance fidelity of the rendering was validated through psychophysical methods. For this task, observers were asked to evaluate the most important visual attributes that directly affect the appearance of effect coatings, i.e., color, the angular dependence of color (color flop), and visual texture (sparkle and graininess). Observers were asked to directly compare the rendered samples with the real samples inside the Byko-spectra effect light booth. The visual validation was performed in three different steps. In the first study, the accuracy of rendering the color of solid samples is evaluated. In a second step, the accuracy of rendering the color flop of effect coatings is validated by conducting two separate visual tests, by using flat and curved samples respectively. In the third and last step, the digital reproduction of both color and texture of metallic samples is tested, by including texture effects in the rendering by using a sparkle visualization model. The parameters of the sparkle visualization model were optimized based on sparkle measurement data from the BYK-mac i instrument using a matrix-adjustment model. Results from the visual evaluations prove the high color accuracy of the developed rendering tool. In the first test, the visual acceptability of the rendering was 80%. This percentage is much better than what was found in a previous investigation using the default sRGB color encoding space. Results of the second study show an improved accuracy when curved samples were used (acceptability of 93% vs 80%). The final visual test shows high visual acceptability of the rendering at 90%. In conclusion, this thesis provides a method for accurate digital simulation of effect coatings, by developing a multispectral and physically based rendering approach on a simple iPad tablet computer. The research developed in this thesis comes with many advances in the scientific and industrial levels, with a great contribution to the development of innovative tools for digitization of materials, as needed in today’s society. / This thesis was carried out under the financial assistance of the Spanish Ministry of Economy and Competitiveness through the pre-doctoral fellowship FPIBES-2016-077325, and the research projects DPI2015-65814-R and RTI2018-096000-B-I00.

<p dir="ltr">Polarization and spectral imaging technology has wide application prospects and economic value in environmental detection, target recognition, remote sensing detection and industrial detection. However, the acquisition of hyperspectral or spectro-polarimetric imaging data is difficult and expensive in general. This study aims to develop a synthetic thermal imaging dataset using computer simulation. The study seeks to explore the simulation performance of Monte-Carlo path tracing algorithm in the fields of spectroscopy and thermal imaging. The goal is to provide a novel tool for effective and accurate dataset generation for thermal imaging neural networks training.</p>