Interactive refractive rendering for gemstones.

Lee Hoi Chi Angie.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 81-86).Abstracts in English and Chinese.Abstract --- p.i摘要 --- p.iiAcknowledgements --- p.iiiTable of Content --- p.ivList of Figures --- p.viiList of Tables --- p.ixChapter 1 --- Introduction --- p.1Chapter 2 --- Previous Work --- p.3Chapter 2.1 --- Geometry Based Rendering --- p.3Chapter 2.1.1 --- Real-Time Shading model --- p.4Chapter 2.1.2 --- Ray Tracing --- p.4Chapter 2.1.2.1 --- Volume absorption --- p.5Chapter 2.1.2.2 --- Light Dispersion --- p.7Chapter 2.2 --- Image Based Rendering --- p.8Chapter 2.2.1 --- Environment mapping --- p.9Chapter 2.2.2 --- Light field Rendering --- p.10Chapter 2.2.3 --- Hardware Acceleration --- p.12Chapter 3 --- Gemstones --- p.14Chapter 3.1 --- Basic optical properties --- p.14Chapter 3.2 --- Cutting --- p.17Chapter 3.3 --- Gemstone model in the proposed system --- p.18Chapter 4 --- Ray Tracing --- p.19Chapter 4.1 --- Forward ray tracing --- p.19Chapter 4.2 --- Backward ray tracing --- p.20Chapter 4.3 --- Recursive ray tracing --- p.21Chapter 4.4 --- Ray tracing Algorithm --- p.22Chapter 4.4.1 --- Ray/ Plane Intersection Calculation --- p.23Chapter 4.4.2 --- Shading Equation --- p.23Chapter 4.4.2.1 --- Ambient Lighting --- p.24Chapter 4.4.2.2 --- Diffuse Reflection --- p.24Chapter 4.4.2.3 --- Specular Reflection --- p.24Chapter 4.4.2.4 --- Specular transmission --- p.26Chapter 4.4.3 --- Fresnel equations --- p.27Chapter 5 --- The Pre-computation stage --- p.29Chapter 5.1 --- Ray tracer --- p.29Chapter 5.1.1 --- Simplifications --- p.30Chapter 5.2 --- Representing Position and Direction of Rays --- p.32Chapter 5.2.1 --- Ray-list --- p.33Chapter 6 --- The Shading stage --- p.36Chapter 6.1 --- Data retrieving process --- p.36Chapter 6.2 --- Illumination equation --- p.36Chapter 6.2.1 --- R-factor and T-factor --- p.37Chapter 6.2.2 --- Illuminations from light source --- p.37Chapter 6.2.2.1 --- Diffuse reflection --- p.38Chapter 6.2.2.2 --- Specular reflection --- p.38Chapter 6.2.2.3 --- Specular transmission --- p.38Chapter 6.2.2.4 --- Light Obstruction Test --- p.40Chapter 6.2.3 --- Illumination from environment --- p.41Chapter 6.2.3.1 --- Virtual Cube --- p.41Chapter 6.2.3.2 --- Refraction map of the environment --- p.43Chapter 6.2.4 --- Total illumination --- p.44Chapter 7 --- Implementation --- p.45Chapter 7.1 --- The Gemstone model --- p.45Chapter 7.2 --- Pre-computation Stage --- p.47Chapter 7.3 --- Shading Stage --- p.48Chapter 8 --- Result --- p.55Chapter 8.1 --- Variables setting --- p.55Chapter 8.1.1 --- R-factor and T-factor --- p.55Chapter 8.1.2 --- Specular reflection constant ks --- p.56Chapter 8.1.3 --- Color and orientation --- p.56Chapter 8.1.4 --- Lighting --- p.57Chapter 8.1.5 --- Refractive index --- p.58Chapter 8.1.6 --- Transparency --- p.59Chapter 8.1.7 --- Background --- p.60Chapter 8.2 --- Computational speed --- p.61Chapter 8.2.1 --- Analytical results --- p.61Chapter 8.2.1.1 --- Pre-computation stage --- p.61Chapter 8.2.1.2 --- Shading stage --- p.62Chapter 8.2.2 --- Experimental results --- p.62Chapter 8.2.2.1 --- Varying number of polygons --- p.62Chapter 8.2.2.2 --- Varying the image size --- p.66Chapter 8.2.2.3 --- Varying the of number of internal reflection --- p.68Chapter 8.3 --- Comparison --- p.71Chapter 8.3.1 --- Comparing with real images of gemstone --- p.71Chapter 8.3.2 --- Comparing with images created by other renderers --- p.73Chapter 8.3.2.1 --- Phong shading model --- p.73Chapter 8.3.2.2 --- Design software --- p.74Chapter 8.3.2.3 --- Web application software --- p.75Chapter 9 --- Conclusion and Future work --- p.77Chapter 9.1 --- Conclusion --- p.77Chapter 9.2 --- Future work --- p.78Reference --- p.8

Reconstruction and rendering of time-varying natural phenomena

While computer performance increases and computer generated images get ever more realistic, the need for modeling computer graphics content is becoming stronger. To achieve photo-realism detailed scenes have to be modeled often with a significant amount of manual labour. Interdisciplinary research combining the fields of Computer Graphics, Computer Vision and Scientific Computing has led to the development of (semi-)automatic modeling tools freeing the user of labour-intensive modeling tasks. The modeling of animated content is especially challenging. Realistic motion is necessary to convince the audience of computer games, movies with mixed reality content and augmented reality applications. The goal of this thesis is to investigate automated modeling techniques for time-varying natural phenomena. The results of the presented methods are animated, three-dimensional computer models of fire, smoke and fluid flows.Durch die steigende Rechenkapazität moderner Computer besteht die Möglichkeit immer realistischere Bilder virtuell zu erzeugen. Dadurch entsteht ein größerer Bedarf an Modellierungsarbeit um die nötigen Objekte virtuell zu beschreiben. Um photorealistische Bilder erzeugen zu können müssen sehr detaillierte Szenen, oft in mühsamer Handarbeit, modelliert werden. Ein interdisziplinärer Forschungszweig, der Computergrafik, Bildverarbeitung und Wissenschaftliches Rechnen verbindet, hat in den letzten Jahren die Entwicklung von (semi-)automatischen Methoden zur Modellierung von Computergrafikinhalten vorangetrieben. Die Modellierung dynamischer Inhalte ist dabei eine besonders anspruchsvolle Aufgabe, da realistische Bewegungsabläufe sehr wichtig für eine überzeugende Darstellung von Computergrafikinhalten in Filmen, Computerspielen oder Augmented-Reality Anwendungen sind. Das Ziel dieser Arbeit ist es automatische Modellierungsmethoden für dynamische Naturerscheinungen wie Wasserfluss, Feuer, Rauch und die Bewegung erhitzter Luft zu entwickeln. Das Resultat der entwickelten Methoden sind dabei dynamische, dreidimensionale Computergrafikmodelle

Towards Predictive Rendering in Virtual Reality

The strive for generating predictive images, i.e., images representing radiometrically correct renditions of reality, has been a longstanding problem in computer graphics. The exactness of such images is extremely important for Virtual Reality applications like Virtual Prototyping, where users need to make decisions impacting large investments based on the simulated images. Unfortunately, generation of predictive imagery is still an unsolved problem due to manifold reasons, especially if real-time restrictions apply. First, existing scenes used for rendering are not modeled accurately enough to create predictive images. Second, even with huge computational efforts existing rendering algorithms are not able to produce radiometrically correct images. Third, current display devices need to convert rendered images into some low-dimensional color space, which prohibits display of radiometrically correct images. Overcoming these limitations is the focus of current state-of-the-art research. This thesis also contributes to this task. First, it briefly introduces the necessary background and identifies the steps required for real-time predictive image generation. Then, existing techniques targeting these steps are presented and their limitations are pointed out. To solve some of the remaining problems, novel techniques are proposed. They cover various steps in the predictive image generation process, ranging from accurate scene modeling over efficient data representation to high-quality, real-time rendering. A special focus of this thesis lays on real-time generation of predictive images using bidirectional texture functions (BTFs), i.e., very accurate representations for spatially varying surface materials. The techniques proposed by this thesis enable efficient handling of BTFs by compressing the huge amount of data contained in this material representation, applying them to geometric surfaces using texture and BTF synthesis techniques, and rendering BTF covered objects in real-time. Further approaches proposed in this thesis target inclusion of real-time global illumination effects or more efficient rendering using novel level-of-detail representations for geometric objects. Finally, this thesis assesses the rendering quality achievable with BTF materials, indicating a significant increase in realism but also confirming the remainder of problems to be solved to achieve truly predictive image generation