A Microfacet‐based Hair Scattering Model

The development of scattering models and rendering algorithms for human hair remains an important area of research in computer graphics. Virtually all available models for scattering off hair or fur fibers are based on separable lobes, which bring practical advantages in importance sampling, but do not represent physically-plausible microgeometry. In this paper, we contribute the first microfacet-based hair scattering model. Based on a rough cylinder geometry with tilted cuticle scales, our far-field model is non-separable by nature, yet allows accurate importance sampling. Additional benefits include support for elliptical hair cross-sections and an analytical solution for the reflected lobe using the GGX distribution. We show that our model captures glint-like forward scattering features in the R lobe that have been observed before but not properly explained

Dynamic hair aging system

The modeling and rendering of hair in Computer Graphics has seen a lot of progress in the last few years. However, there has not been much progress on the modeling and rendering on the subject of hair aging. This work aims to simulate the hair aging phenomena by developing a procedural shader using Blender as the development platform. The project is based on the biology of hair and the results show that our system is capable of creating visually realistic hair aging

Photorealistic physically based render engines: a comparative study

Pérez Roig, F. (2012). Photorealistic physically based render engines: a comparative study. http://hdl.handle.net/10251/14797.Archivo delegad

Simulation of 3D Model, Shape, and Appearance Aging by Physical, Chemical, Biological, Environmental, and Weathering Effects

Physical, chemical, biological, environmental, and weathering effects produce a range of 3D model, shape, and appearance changes. Time introduces an assortment of aging, weathering, and decay processes such as dust, mold, patina, and fractures. These time-varying imperfections provide the viewer with important visual cues for realism and age. Existing approaches that create realistic aging effects still require an excessive amount of time and effort by extremely skilled artists to tediously hand fashion blemishes or simulate simple procedural rules. Most techniques do not scale well to large virtual environments. These limitations have prevented widespread utilization of many aging and weathering algorithms. We introduce a novel method for geometrically and visually simulating these processes in order to create visually realistic scenes. This work proposes the ``mu-ton system, a framework for scattering numerous mu-ton particles throughout an environment to mutate and age the world. We take a point based representation to discretize both the decay effects and the underlying geometry. The mu-ton particles simulate interactions between multiple phenomena. This mutation process changes both the physical properties of the external surface layer and the internal volume substrate. The mutation may add or subtract imperfections into the environment as objects age. First we review related work in aging and weathering, and illustrate the limitations of the current data-driven and physically based approaches. We provide a taxonomy of aging processes. We then describe the structure for our ``mu-ton framework, and we provide the user a short tutorial how to setup different effects. The first application of the ``mu-ton system focuses on inorganic aging and decay. We demonstrate changing material properties on a variety of objects, and simulate their transformation. We show the application of our system aging a simple city alley on different materials. The second application of the ``mu-ton system focuses organic aging. We provide details on simulating a variety of growth processes. We then evaluate and analyze the ``mu-ton framework and compare our results with ``gamma-ton tracing. Finally, we outline the contributions this thesis provides to computer-based aging and weathering simulation

State of the Art on Stylized Fabrication

© 2018 The Authors Computer Graphics Forum © 2018 The Eurographics Association and John Wiley & Sons Ltd. Digital fabrication devices are powerful tools for creating tangible reproductions of 3D digital models. Most available printing technologies aim at producing an accurate copy of a tridimensional shape. However, fabrication technologies can also be used to create a stylistic representation of a digital shape. We refer to this class of methods as ‘stylized fabrication methods’. These methods abstract geometric and physical features of a given shape to create an unconventional representation, to produce an optical illusion or to devise a particular interaction with the fabricated model. In this state-of-the-art report, we classify and overview this broad and emerging class of approaches and also propose possible directions for future research

Production of 3D animated short films in Unity 5 : can game engines replace the traditional methods?

In 3D animation cinema, the elements of a scene are created by artists using computer software. To generate the final result, there must be a conversion (rendering) of the threedimensional models to two-dimensional images (frames) that will later be joined together and edited into a video format. 3D animation films have traditionally been rendered using pre-rendering engines, a time consuming and expensive process that usually requires the use of multiple computers rendering at the same time (render farms), renders which may need to be repeated if the results are not ideal. Videogames, on the other hand, are reactive applications where the player may have different possible courses of action that will generate distinct results. In those cases, it is necessary that the engine waits for the player’s input before it calculates the following frames. To allow for fast calculations in real time, 3D game developers use game engines that incorporate real time rendering methods which can generate images much faster than the prerendering engines mentioned above. To be able to generate a large number of frames per second, there must be an optimization of the entire scene, in order to reduce the number of necessary calculations. That optimization is created by using techniques, practices and tools that are not commonly used by animation cinema professionals. Due to that optimization necessity, videogames always had a lower graphic quality than that of animated films, where each frame is rendered separately and takes as long as necessary to obtain the required result. Physically Based Rendering (PBR) technology is one of the methods incorporated by some rendering engines for the generation of physically accurate results, using calculations that follow the laws of physics as it happens in the real world and creating more realistic images which require less effort, not only from the artist but also from the equipment. The incorporation of PBR in game engines allowed for high graphic quality generated results in real time, gradually closing the visual quality gap between videogames and animated cinema. Recently, game engines such as Unity and Unreal Engine started to be used – mostly by the companies that created the engine, as a proof of concept – for rendering 3D animated films. This could lead to changes in the animation cinema production methods by the studios that, until now, have used traditional pre-rendering methods.No cinema de animação 3D, os elementos de uma cena são criados por artistas através da utilização de programas de computador. Para gerar o resultado final, é necessário fazer-se uma conversão (render) dos modelos tri-dimensionais para imagens bi-dimensionais (frames), que posteriormente serão unidas e editadas para um formato de vídeo. Tradicionalmente, o rendering de filmes de animação 3D é feita através de motores de pre-rendering, um processo demorado e dispendioso que geralmente requer a utilização de múltiplos computadores a trabalhar em simultâneo (render farms), e que poderá ter que ser repetido caso os resultados obtidos não sejam ideais. Os videojogos, por outro lado, são aplicações reactivas, onde o jogador pode ter várias sequências de acções, que poderão gerar resultados distintos. Nesses casos, é necessário o motor de jogo esperar pela acção do jogador antes de calcular as imagens seguintes. Para possibilitar cálculos rápidos em tempo-real, os criadores de jogos 3D usam motores de jogo que incorporam métodos de renderização em tempo-real que conseguem gerar imagens muito mais rápido do que os motores de pre-rendering mencionados acima. Para conseguir gerar um grande número de imagens por segundo, é necessário existir uma optimização de toda a cena, para reduzir o número de cálculos necessários. Essa optimização é criada através da utilização de técnicas, práticas e ferramentas que, geralmente, não são utiliadas por profissionais da área de cinema de animação. Devido a essa necessidade de optimização, os videojogos sempre tiveram uma qualidade gráfica inferior à dos filmes de animação, onde o render de cada imagem é gerado separadamente e pode levar tanto tempo quanto for necessário para obter o resultado desejado. A tecnologia de Rendering Baseado em Física (Physically Based Rendering – PBR) é um dos métodos incorporados por alguns motores de rendering para a geração de resultados físicamente correctos, usando cálculos que seguem as leis da física, tal como acontece no mundo real e criando imagens mais realistas necessitando de menos esforço, não só da parte do artista mas também do equipamento. A incorporação de PBR em motores de jogo possibilitou resultados gerados em tempo-real com grande qualidade gráfica, o que gradualmente vai aproximando a qualidade visual dos videojogos à do cinema de animação. Recentemente, motores de jogo como o Unity e o Unreal Engine começaram a ser utilizados – maioritariamente pelas companhias que criaram o motor de jogo, como prova de conceito – para renderização de filmes de animação 3D. Este passo poderá levar a mudanças nos métodos de produção do cinema de animação em estúdios que, até agora, utilizaram métodos de pré-renderização tradicionais

Non-photorealistic rendering: a critical examination and proposed system.

In the first part of the program the emergent field of Non-Photorealistic Rendering is explored from a cultural perspective. This is to establish a clear understanding of what Non-Photorealistic Rendering (NPR) ought to be in its mature form in order to provide goals and an overall infrastructure for future development. This thesis claims that unless we understand and clarify NPR's relationship with other media (photography, photorealistic computer graphics and traditional media) we will continue to manufacture "new solutions" to computer based imaging which are confused and naive in their goals. Such solutions will be rejected by the art and design community, generally condemned as novelties of little cultural worth ( i.e. they will not sell). This is achieved by critically reviewing published systems that are naively described as Non-photorealistic or "painterly" systems. Current practices and techniques are criticised in terms of their low ability to articulate meaning in images; solutions to this problem are given. A further argument claims that NPR, while being similar to traditional "natural media" techniques in certain aspects, is fundamentally different in other ways. This similarity has lead NPR to be sometimes proposed as "painting simulation" — something it can never be. Methods for avoiding this position are proposed. The similarities and differences to painting and drawing are presented and NPR's relationship to its other counterpart, Photorealistic Rendering (PR), is then delineated. It is shown that NPR is paradigmatically different to other forms of representation — i.e. it is not an "effect", but rather something basically different. The benefits of NPR in its mature form are discussed in the context of Architectural Representation and Design in general. This is done in conjunction with consultations with designers and architects. From this consultation a "wish-list" of capabilities is compiled by way of a requirements capture for a proposed system. A series of computer-based experiments resulting in the systems "Expressive Marks" and 'Magic Painter" are carried out; these practical experiments add further understanding to the problems of NPR. The exploration concludes with a prototype system "Piranesi" which is submitted as a good overall solution to the problem of NPR. In support of this written thesis are : - • The Expressive Marks system • Magic Painter system • The Piranesi system (which includes the EPixel and Sketcher systems) • A large portfolio of images generated throughout the exploration

Animating Unpredictable Effects

Uncanny computer-generated animations of splashing waves, billowing smoke clouds, and characters’ flowing hair have become a ubiquitous presence on screens of all types since the 1980s. This Open Access book charts the history of these digital moving images and the software tools that make them. Unpredictable Visual Effects uncovers an institutional and industrial history that saw media industries conducting more private R&D as Cold War federal funding began to wane in the late 1980s. In this context studios and media software companies took concepts used for studying and managing unpredictable systems like markets, weather, and fluids and turned them into tools for animation. Unpredictable Visual Effects theorizes how these animations are part of a paradigm of control evident across society, while at the same time exploring what they can teach us about the relationship between making and knowing

BxDF material acquisition, representation, and rendering for VR and design

Photorealistic and physically-based rendering of real-world environments with high fidelity materials is important to a range of applications, including special effects, architectural modelling, cultural heritage, computer games, automotive design, and virtual reality (VR). Our perception of the world depends on lighting and surface material characteristics, which determine how the light is reflected, scattered, and absorbed. In order to reproduce appearance, we must therefore understand all the ways objects interact with light, and the acquisition and representation of materials has thus been an important part of computer graphics from early days. Nevertheless, no material model nor acquisition setup is without limitations in terms of the variety of materials represented, and different approaches vary widely in terms of compatibility and ease of use. In this course, we describe the state of the art in material appearance acquisition and modelling, ranging from mathematical BSDFs to data-driven capture and representation of anisotropic materials, and volumetric/thread models for patterned fabrics. We further address the problem of material appearance constancy across different rendering platforms. We present two case studies in architectural and interior design. The first study demonstrates Yulio, a new platform for the creation, delivery, and visualization of acquired material models and reverse engineered cloth models in immersive VR experiences. The second study shows an end-to-end process of capture and data-driven BSDF representation using the physically-based Radiance system for lighting simulation and rendering