No description available.

The sole purpose of every form of visual representation is to make something look believable. Even among abstract or conceptual representation, the purpose is to create something that within the defined visual language the audience will consider believable and accepted. In the field of computer generated representation there are numerous visual languages that have been developed throughout the years, attempting to solve different visualization or artistic problems. This thesis presents an alternative light transfer model for participating media focused on the intuitive control of the illumination data and the artistic value of the resulting image. The purpose is not focused on accurately modeling lights physical behavior and its interaction with the surfaces and elements. My thesis describes an artistic approach which aims to offer an organic and intuitive control of the glow and temperature of the effects of participating media and direct the value and hues through the surfaces. The system described in the thesis approximates light transfer through a given volume by calculating light contribution in the volume with discreet sampling and subsequently gathering these values to determine the diffuse scattering contribution for the volume. I will also discuss the assumptions made to allow such approximations, as well as how the intuitive control offered by the approach and these approximations allow new forms or representation and artistic direction.

Rendering of skin and translucent materials as a real-time solution for a game engine.

Context Subsurface scattering - the effect of light scattering within a material. Lots of materials on earth possess translucent properties. It is therefore an important factor to consider when trying to render realistic images. Historically the effect has been used for offline rendering with ray tracers, but is now considered a real-time rendering technique and is done based on approximations off previous models. Early real-time methods approximates the effect in object texture space which does not scale well with real-time applications such as games. A relatively new approach makes it possible to apply the effect as a post processing effect using GPGPU capabilities, making this approach compatible with most modern rendering pipelines. Objectives The aim of this thesis is to explore the possibilities of a dynamic real-time solution to subsurface scattering with a modern rendering API to utilize GPGPU programming and modern data management, combined with previous techniques Methods The proposed subsurface scattering technique is implemented in a delimited real-time graphics engine using a modern rendering API to evaluate the impact on performance by conducting several experiments with specific properties. Results The result obtained hints that by using a flexible solution to represent materials, execution time lands at an acceptable rate and could be used in real-time. These results shows that the execution time grows nearly linearly with consideration to the number of layers and the strength of the effect. Because the technique is performed in screen space, the performance scales with subsurface scattering screen coverage and screen resolution. Conclusions The technique could be used in real-time and could trivially be integrated to most existing rendering pipelines. Further research and testing should be done in order to determine how the effect scales in a complex 3D-game environment.

This diploma thesis deals with design of 3D scanner for scanning problematic surfaces. The research part introduces the problem of 3D scanning and describes causes of random errors. Further, it contains a description and division of methods that leads to their elimination. The practical part of the thesis deals with design and description of hardware and software parts of the 3D scanner. The output of this work is device that is able to implement and compare quality of codification methods mainly for scanning of problematic surfaces. The functionality of equipment was verified by experimental measurement.

No description available.

In this thesis, a new improved V-Ray subsurface scattering shader based on the improved diffusion theory is proposed. The new shader supports the better dipole and the quantized diffusion reflectance model for layered translucent materials. These new implemented models build on previous diffusion BSSRDFs and in the case of quantized diffusion uses an extended source function for the material layer. One of the main contributions and significant improvement over V-Ray’s existing subsurface scattering shader is the front and back subsurface scattering separation. This was achieved by dividing the illumination map that is used to calculate each shading’s point color, in two parts: the front part that comes of front lighting and the back one that comes of back lighting. Thus, the subsurface scattering layer can be divided in its consisting parts and each of them can be controlled, weighted and used independently. Finally, the project’s outcome is a new V-Ray material that provides all the above improvements in an intuitive, practical and efficient shader with several intuitive algorithm and light map controls, where artists can create subsurface scattering effects through three subsurface scattering layers.

Practical laser triangulation sessions were performed for each measurement object to obtain ground truth data. Three methods for laser line simulations were implemented: reshaping the built-in light sources of Blender, creating a texture projector and approximating a Gaussian beam as a light emitting volume. The camera simulation was based on the default camera of Blender together with settings from the physical camera. Three approaches for creating wood material were tested: procedural texturing, using microscopic image textures to create 3D-material and UV-mapping high resolution photograph onto the geometry. The blister package was simulated with one material for the pills and another for the semi-transparent plastic packaging. A stand-alone Python script was implemented to simulate anisotropic/directed subsurface scattering of a point laser in wood. This algorithm included an approach for creating vector fields that represented subsurface scattering directions. Three post-processing scripts were produced to simulate sensor noise, blurring/blooming of the laser line and lastly to apply simulated speckle patterns to the laser lines. Sensor images were simulated by rendering a laser line projected onto a measurement object. The sensor images were post-processed with the three mentioned scripts. Thousands of sensor images were simulated, with a small displacement of the measurement object between each image. After post-processing, these images were combined to a single scattering image. SICK IVP AB provided the algorithms needed for laser centre extraction as well as for scattering image creation. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>

We present an implicit approach for constructing smooth isolated or interconnected 3-D inscribed volumes which can be employed for volumetric modeling of various kinds of spongy or porous structures, such as volcanic rocks, pumice stones, Cancellus bones *, liquid or dry foam, radiolarians, cheese, and other similar materials. The inscribed volumes can be represented in their normal or positive forms to model natural pebbles or pearls, or in their inverted or negative forms to be used in porous structures, but regardless of their types, their smoothness and sizes are controlled by the user without losing the consistency of the shapes. We introduce two techniques for blending and creating interconnections between these inscribed volumes to achieve a great flexibility to adapt our approach to different types of porous structures, whether they are regular or irregular. We begin with a set of convex polytopes such as 3-D Voronoi diagram cells and compute inscribed volumes bounded by the cells. The cells can be irregular in shape, scale, and topology, and this irregularity transfers to the inscribed volumes, producing natural-looking spongy structures. Describing the inscribed volumes with implicit functions gives us a freedom to exploit volumetric surface combinations and deformations operations effortlessly / Graduate

En synthèse d’images, reproduire les effets complexes de la lumière sur des matériaux transluminescents, tels que la cire, le marbre ou la peau, contribue grandement au réalisme d’une image. Malheureusement, ce réalisme supplémentaire est couteux en temps de calcul. Les modèles basés sur la théorie de la diffusion visent à réduire ce coût en simulant le comportement physique du transport de la lumière sous surfacique tout en imposant des contraintes de variation sur la lumière incidente et sortante. Une composante importante de ces modèles est leur application à évaluer hiérarchiquement l’intégrale numérique de l’illumination sur la surface d’un objet. Cette thèse révise en premier lieu la littérature actuelle sur la simulation réaliste de la transluminescence, avant d’investiguer plus en profondeur leur application et les extensions des modèles de diffusion en synthèse d’images. Ainsi, nous proposons et évaluons une nouvelle technique d’intégration numérique hiérarchique utilisant une nouvelle analyse fréquentielle de la lumière sortante et incidente pour adapter efficacement le taux d’échantillonnage pendant l’intégration. Nous appliquons cette théorie à plusieurs modèles qui correspondent à l’état de l’art en diffusion, octroyant une amélioration possible à leur efficacité et précision. / In image synthesis, reproducing the complex appearance of objects with subsurface light scattering, such as wax, marble and skin, greatly contributes to the realism of an image. Unfortunately, this added realism comes at a high computational cost. Models based on diffusion theory aim to reduce this computational cost by simulating the physical behaviour of subsurface light scattering while imposing smoothness constraints on the incident and outgoing light fields. An important component of these models is how they are employed to hierarchically evaluate the numerical integral of lighting over the surface of an object. This thesis will first review the existing literature on realistic subsurface lighting simulation, before investigating in more depth the application and extension of modern diffusion models in image synthesis. In doing so, we propose and evaluate a new hierarchical numerical integration technique that uses a novel frequency analysis of the incident and outgoing light fields to reliably adapt the sampling rate during integration. We realize our resulting theory in the context of several state-of-the-art diffusion models, providing a marked improvement in their efficiency and accuracy.