Subdivision surface fitting to a dense mesh using ridges and umbilics

Fitting a sparse surface to approximate vast dense data is of interest for many applications: reverse engineering, recognition and compression, etc. The present work provides an approach to fit a Loop subdivision surface to a dense triangular mesh of arbitrary topology, whilst preserving and aligning the original features. The natural ridge-joined connectivity of umbilics and ridge-crossings is used as the connectivity of the control mesh for subdivision, so that the edges follow salient features on the surface. Furthermore, the chosen features and connectivity characterise the overall shape of the original mesh, since ridges capture extreme principal curvatures and ridges start and end at umbilics. A metric of Hausdorff distance including curvature vectors is proposed and implemented in a distance transform algorithm to construct the connectivity. Ridge-colour matching is introduced as a criterion for edge flipping to improve feature alignment. Several examples are provided to demonstrate the feature-preserving capability of the proposed approach

Interactive Video Game Content Authoring using Procedural Methods

This thesis explores avenues for improving the quality and detail of game graphics, in the context of constraints that are common to most game development studios. The research begins by identifying two dominant constraints; limitations in the capacity of target gaming hardware/platforms, and processes that hinder the productivity of game art/content creation. From these constraints, themes were derived which directed the research‟s focus. These include the use of algorithmic or „procedural‟ methods in the creation of graphics content for games, and the use of an „interactive‟ content creation strategy, to better facilitate artist production workflow. Interactive workflow represents an emerging paradigm shift in content creation processes used by the industry, which directly integrates game rendering technology into the content authoring process. The primary motivation for this is to provide „high frequency‟ visual feedback that enables artists to see games content in context, during the authoring process. By merging these themes, this research develops a production strategy that takes advantage of „high frequency feedback‟ in an interactive workflow, to directly expose procedural methods to artists‟, for use in the content creation process. Procedural methods have a characteristically small „memory footprint‟ and are capable of generating massive volumes of data. Their small „size to data volume‟ ratio makes them particularly well suited for use in game rendering situations, where capacity constraints are an issue. In addition, an interactive authoring environment is well suited to the task of setting parameters for procedural methods, reducing a major barrier to their acceptance by artists. An interactive content authoring environment was developed during this research. Two algorithms were designed and implemented. These algorithms provide artists‟ with abstract mechanisms which accelerate common game content development processes; namely object placement in game environments, and the delivery of variation between similar game objects. In keeping with the theme of this research, the core functionality of these algorithms is delivered via procedural methods. Through this, production overhead that is associated with these content development processes is essentially offloaded from artists onto the processing capability of modern gaming hardware. This research shows how procedurally based content authoring algorithms not only harmonize with the issues of hardware capacity constraints, but also make the authoring of larger and more detailed volumes of games content more feasible in the game production process. Algorithms and ideas developed during this research demonstrate the use of procedurally based, interactive content creation, towards improving detail and complexity in the graphics of games

Physically Based Tree Rendering

This project produced and rendered physically based models of several tree species in real time. This was accomplished by procedurally generating a branch hierarchy and leaves within some bounding volumes according to rules that define a tree species. Multiple trees can be rendered at interactive frame rates greater than 45 frames per second. This enables the production of more realistic forests in games and visual applications procedurally and also frees up disk space for other resources because large model files of trees do not need to be stored on disk

Transition Contour Synthesis with Dynamic Patch Transitions

In this article, we present a novel approach for modulating the shape of transitions between terrain materials to produce detailed and varied contours where blend resolution is limited. Whereas texture splatting and blend mapping add detail to transitions at the texel level, our approach addresses the broader shape of the transition by introducing intermittency and irregularity. Our results have proven that enriched detail of the blend contour can be achieved with a performance competitive to existing approaches without additional texture, geometry resources, or asset preprocessing. We achieve this by compositing blend masks on-the-fly with the subdivision of texture space into differently sized patches to produce irregular contours from minimal artistic input. Our approach is of particular importance for applications where GPU resources or artistic input is limited or impractical

Real-time rendering and simulation of trees and snow

Tree models created by an industry used package are exported and the structure extracted in order to procedurally regenerate the geometric mesh, addressing the limitations of the application's standard output. The structure, once extracted, is used to fully generate a high quality skeleton for the tree, individually representing each section in every branch to give the greatest achievable level of freedom of deformation and animation. Around the generated skeleton, a new geometric mesh is wrapped using a single, continuous surface resulting in the removal of intersection based render artefacts. Surface smoothing and enhanced detail is added to the model dynamically using the GPU enhanced tessellation engine. A real-time snow accumulation system is developed to generate snow cover on a dynamic, animated scene. Occlusion techniques are used to project snow accumulating faces and map exposed areas to applied accumulation maps in the form of dynamic textures. Accumulation maps are xed to applied surfaces, allowing moving objects to maintain accumulated snow cover. Mesh generation is performed dynamically during the rendering pass using surface o�setting and tessellation to enhance required detail

Evaluating Tessellation and Screen-Space Ambient Occlusion in WebGL-Based Real-Time Application

abstract: Tessellation and Screen-Space Ambient Occlusion are algorithms which have been widely-used in real-time rendering in the past decade. They aim to enhance the details of the mesh, cast better shadow effects and improve the quality of the rendered images in real time. WebGL is a web-based graphics library derived from OpenGL ES used for rendering in web applications. It is relatively new and has been rapidly evolving, this has resulted in it supporting a subset of rendering features normally supported by desktop applications. In this thesis, the research is focusing on evaluating Curved PN-Triangles tessellation with Screen Space Ambient Occlusion (SSAO), Horizon-Based Ambient Occlusion (HBAO) and Horizon-Based Ambient Occlusion Plus (HBAO+) in WebGL-based real-time application and comparing its performance to desktop based application and to discuss the capabilities, limitations and bottlenecks of WebGL 1.0.Dissertation/ThesisWebGL ProgramOpenGL ProgramMasters Thesis Computer Science 201

Exploring mesh shaders

Dissertação de mestrado integrado em Engenharia InformáticaEvery artist is somewhat limited by the mean by which they expose their art. This is also true for the field of Computer Graphics, where there are many limiting factors that developers must go out of their way to avoid. The most limiting of these factors is the computing performance, which directly limits the complexity of what an artist can fabricate in a piece of hardware. As such, Computer Graphics’ investigators keep an eye out for the improvements made in the hardware department that enables them to introduce more complexity to the scenes they create on their computers. Three years ago, a novel approach to compute the geometric complexity of three-dimensional (3D) scenes was introduced: Mesh shaders. Mesh shaders pose as an alternative to the traditional geometric processing method and can be a more performant approach to handle specific geometric workloads. Notwithstanding, little attention has been given to these shaders. Thus, this thesis presents an investigative effort to evaluate the value proposition of these shaders across different scenarios. To do so, this thesis puts Mesh shaders against traditional implementations and measures their differences both in method and performance. By the end of this thesis, the reader should have a concise understanding of Mesh shaders, but not a clear cut answer regarding their use. These shaders can provide performance benefits in specific scenarios over the traditional approach, but not without considerable care by the developer. In fact, the flexibility provided by the Mesh shaders’ approach gives the developer a significant responsibility regarding their final performance. When incorrectly set up, these shaders can result in mediocre performances compared to those of the traditional pipeline. Ultimately, these shaders should be used by experienced users intending to avoid specific bottlenecks of the traditional approach. For others, the traditional pipeline offers a more streamlined approach, thoroughly optimised by default.Todos os artistas são de alguma forma limitados pelo meio de exposição da sua arte. Isto não deixa de ser verdade com Computação Gráfica, onde existem vários fatores limitadores que os programadores têm de con tornar. Entre estes, o mais impeditivo é a velocidade de computação, que limita diretamente a complexidade da arte que pode ser produzida por uma peça de hardware. Deste modo, os investigadores da área de Computação Gráfica mantêm-se atentos às inovações que ocorrem no campo do hardware e lhes permitem introduzir mais complexidade nos cenários que criam. Há três anos, um método inédito para tratar a complexidade geométrica de cenas tridimensionais foi intro duzido: Mesh shaders. Os Mesh shaders apresentam-se como uma alternativa ao método tradicional de pro cessamento de geometria, que pode obter melhor desempenho em certos cenários geométricos. No entanto, não tem sido dada muita atenção a esta alternativa. Assim, esta tese apresenta uma investigação destes shaders com o intuito de avaliar a sua proposta de valor em diferentes situações. Para o fazer, esta tese irá colocar estes shaders frente a frente com os shaders tradicionais e medirá as diferenças entre ambos, tanto em desempenho como em método. No final, o leitor deverá possuir uma ideia coesa sobre os Mesh shaders, mas não terá uma perceção binária quanto ao uso dos mesmos. Isto porque estes shaders podem oferecer um benefício em termos de desempenho em certas situações, mas requerem cuidados adicionais por parte do programador. Da flexibilidade oferecida pelos Mesh shaders advém uma responsabilidade significativa para o programador no que toca ao desempenho final dos mesmos. Quando programados incorretamente, estes shaders resultarão num desempenho medíocre comparado ao desempenho oferecido pelo método tradicional. Fundamentalmente, estes shaders deverão ser utilizados por utilizadores mais experientes que pretendem evitar bottlenecks específicos do método tradicional. Para todos os outros, o pipeline tradicional oferece um método mais simples que possui por predefinição otimizações acentuadas

Real-time Physics Based Simulation for 3D Computer Graphics

Restoration of realistic animation is a critical part in the area of computer graphics. The goal of this sort of simulation is to imitate the behavior of the transformation in real life to the greatest extent. Physics-based simulation provides a solid background and proficient theories that can be applied in the simulation. In this dissertation, I will present real-time simulations which are physics-based in the area of terrain deformation and ship oscillations. When ground vehicles navigate on soft terrains such as sand, snow and mud, they often leave distinctive tracks. The realistic simulation of such vehicle-terrain interaction is important for ground based visual simulations and many video games. However, the existing research in terrain deformation has not addressed this issue effectively. In this dissertation, I present a new terrain deformation algorithm for simulating vehicle-terrain interaction in real time. The algorithm is based on the classic terramechanics theories, and calculates terrain deformation according to the vehicle load, velocity, tire size, and soil concentration. As a result, this algorithm can simulate different vehicle tracks on different types of terrains with different vehicle properties. I demonstrate my algorithm by vehicle tracks on soft terrain. In the field of ship oscillation simulation, I propose a new method for simulating ship motions in waves. Although there have been plenty of previous work on physics based fluid-solid simulation, most of these methods are not suitable for real-time applications. In particular, few methods are designed specifically for simulating ship motion in waves. My method is based on physics theories of ship motion, but with necessary simplifications to ensure real-time performance. My results show that this method is well suited to simulate sophisticated ship motions in real time applications

A framework for local terrain deformation based on diffusion theory

Terrains have a key role in making outdoor virtual scenes believable and immersive as they form the support for every other natural element in the scene. Although important, terrains are often given limited interactivity in real-time applications. However, in nature, terrains are dynamic and interact with the rest of the environment changing shape on different levels, from tracks left by a person running on a gravel soil (micro-scale), to avalanches on the side of a mountain (macro-scale). The challenge in representing dynamic terrains correctly is that the soil that forms them is vastly heterogeneous and behaves differently depending on its composition. This heterogeneity introduces difficulties at different levels in dynamic terrains simulations, from modelling the large amount of different elements that compose the oil to simulating their dynamic behaviour. This work presents a novel framework to simulate multi-material dynamic terrains by taking into account the soil composition and its heterogeneity. In the proposed framework soil information is obtained from a material description map applied to the terrain mesh. This information is used to compute deformations in the area of interaction using a novel mathematical model based on diffusion theory. The deformations are applied to the terrain mesh in different ways depending on the distance of the area of interaction from the camera and the soil material. Deformations away from the camera are simulated by dynamically displacing normals. While deformations in a neighbourhood of the camera are represented by displacing the terrain mesh, which is locally tessellated to better fit the displacement. For gravel based soils the terrain details are added near the camera by reconstructing the meshes of the small rocks from the texture image, thus simulating both micro and macro-structure of the terrain. The outcome of the framework is a realistic interactive dynamic terrain animation in real-time