The Iray Light Transport Simulation and Rendering System

While ray tracing has become increasingly common and path tracing is well understood by now, a major challenge lies in crafting an easy-to-use and efficient system implementing these technologies. Following a purely physically-based paradigm while still allowing for artistic workflows, the Iray light transport simulation and rendering system allows for rendering complex scenes by the push of a button and thus makes accurate light transport simulation widely available. In this document we discuss the challenges and implementation choices that follow from our primary design decisions, demonstrating that such a rendering system can be made a practical, scalable, and efficient real-world application that has been adopted by various companies across many fields and is in use by many industry professionals today

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

Manipulação interativa de cenas fotorealistas usando path tracing

Rendering pleasing photorealistic images requires both a high-quality renderer and wellcrafted scenes. While rendering algorithms and systems have made some impressive progress over the last two decades, creating nice scenes still remains highly dependent of the artistic skills of the modeler. As a result, researchers tend to rely on a small number of existing good-looking scenes to test their algorithms. While creating new scenes from scratch is difficult for non-artists, editing existing scenes to achieve new and desired results is a task at the reach of the average graphics user. We present a system that allows users with no special artistic skills to create new scenes by modifying existing ones through a simple user interface. Enabled by modern hardware and software advancements, we render the scenes photorealistically using path tracing and provide instant feedback on the user modifications. The quality of the images generated by our system is comparable to established offline renderers, such as PBRT, while still maintaining interactive performance. Our system should stimulate the creation of new scene datasets, and allow anyone to customize existing scenes with shapes and materials according to his/her specific needs or desires. The easy customization of scenes and the high-quality renderings produced by our system may also stimulate other professionals, such as designers, scenographers, architects, decorators, etc. to make more intense use of computer generated imaging in their daily tasks.Renderizar imagens fotorealistas agradáveis requer tanto um renderizador de alta qualidade quanto cenas bem feitas. Enquanto sistemas e algoritmos de rendering tiveram progressos impressionantes nas últimas duas décadas, a criação de cenas interessantes ainda é altamente dependente nas habilidades artísticas do modelador. Como resultado, pesquisadores tendem a usar uma porção pequena de boas cenas já existentes para testar seus algoritmos. Embora a criação de cenas do zero seja difícil para não-artistas, editar cenas existentes para conseguir novos resultados é uma tarefa ao alcance do usuário médio de computação gráfica. Nós apresentamos um sistema que permite usuários sem habilidades artísticas especiais a criar novas cenas modificando cenas existentes através de uma interface simples. Baseado em avanços recentes em hardware e software nós renderizamos as cenas fotorealisticamente usando path tracing, provendo feedback instantâneo nas modificações do usuário. A qualidade das imagens geradas pelo nosso sistema é comparável a renderizadores offline estabelecidos, como o PBRT, enquanto ainda mantendo performance interativa. Nosso sistema deve estimular a criação de novos datasets de cenas, e permitir a qualquer um a customizar cenas existentes com formas e materiais de acordo com sua necessidade ou desejo. A fácil customização de cenas e as imagens de alta qualidade produzidas pelo nosso sistema também podem estimular outros profissionais, como designers, cenógrafos, arquitetus, decoradores, etc. a fazer uso mais intenso de imagens geradas por computador em suas tarefas diárias

Image based surface reflectance remapping for consistent and tool independent material appearence

Physically-based rendering in Computer Graphics requires the knowledge of material properties other than 3D shapes, textures and colors, in order to solve the rendering equation. A number of material models have been developed, since no model is currently able to reproduce the full range of available materials. Although only few material models have been widely adopted in current rendering systems, the lack of standardisation causes several issues in the 3D modelling workflow, leading to a heavy tool dependency of material appearance. In industry, final decisions about products are often based on a virtual prototype, a crucial step for the production pipeline, usually developed by a collaborations among several departments, which exchange data. Unfortunately, exchanged data often tends to differ from the original, when imported into a different application. As a result, delivering consistent visual results requires time, labour and computational cost. This thesis begins with an examination of the current state of the art in material appearance representation and capture, in order to identify a suitable strategy to tackle material appearance consistency. Automatic solutions to this problem are suggested in this work, accounting for the constraints of real-world scenarios, where the only available information is a reference rendering and the renderer used to obtain it, with no access to the implementation of the shaders. In particular, two image-based frameworks are proposed, working under these constraints. The first one, validated by means of perceptual studies, is aimed to the remapping of BRDF parameters and useful when the parameters used for the reference rendering are available. The second one provides consistent material appearance across different renderers, even when the parameters used for the reference are unknown. It allows the selection of an arbitrary reference rendering tool, and manipulates the output of other renderers in order to be consistent with the reference

Um ambiente para desevonvoimento de algoritmos de amostragem e remoção de ruído

In the context of Monte Carlo rendering, although many sampling and denoising techniques have been proposed in the last few years, the case for which one should be used for a specific scene is still to be made. Moreover, developing a new technique has required selecting a particular rendering system, which makes the technique tightly coupled to the chosen renderer and limits the amount of scenes it can be tested on. In this work, we propose a renderer-agnostic framework for developing and benchmarking sampling and denoising techniques for Monte Carlo rendering. It decouples techniques from rendering systems by hiding the renderer details behind a general API. This improves productivity and allows for direct comparisons among techniques using scenes from different rendering systems. The proposed framework contains two main parts: a software development kit that helps users to develop and and test their techniques locally, and an online system that allows users to submit their techniques and have them automatically benchmarked on our servers. We demonstrate its effectiveness by using our API to instrument four rendering systems and a variety of Monte Carlo denoising techniques — including recent learning-based ones — and performing a benchmark across different rendering systems.No contexto de Monte Carlo rendering, apesar de diversas técnicas de amostragem e remoção de ruído tenham sido propostas nos últimos anos, aportar qual técnica deve ser usada para uma cena específica ainda é uma tarefa difícil. Além disso, desenvolver uma nova técnica requer escolher um renderizador em particular, o que torna a técnica dependente do renderizador escolhido e limita a quantidade de cenas disponíveis para testar a técnica. Neste trabalho, um framework para desenvolvimento e avaliação de técnicas de amostragem e remoção de ruído para Monte Carlo rendering é proposto. Ele permite desacoplar as técnicas dos renderizadores por meio de uma API genérica, promovendo a reprodutibilidade e permitindo comparações entre técnicas utilizando-se cenas de diferentes renderizadores. O sistema proposto contém duas partes principais: um kit de desenvolvimento de software que ajuda os usuários a desenvolver e testar suas técnicas localmente, e um sistema online que permite que usuários submetam técnicas para que as mesmas sejam automaticamente avaliadas no nosso servidor. Para demonstramos a efetividade do ambiante proposto, modificamos quatro renderizadores e várias técnicas de remoção de ruído — incluindo técnicas recentes baseadas em aprendizado de máquina — e efetuamos uma avaliação utilizando cenas de diferentes renderizadores

Extracting Triangular 3D Models, Materials, and Lighting From Images

We present an efficient method for joint optimization of topology, materials and lighting from multi-view image observations. Unlike recent multi-view reconstruction approaches, which typically produce entangled 3D representations encoded in neural networks, we output triangle meshes with spatially-varying materials and environment lighting that can be deployed in any traditional graphics engine unmodified. We leverage recent work in differentiable rendering, coordinate-based networks to compactly represent volumetric texturing, alongside differentiable marching tetrahedrons to enable gradient-based optimization directly on the surface mesh. Finally, we introduce a differentiable formulation of the split sum approximation of environment lighting to efficiently recover all-frequency lighting. Experiments show our extracted models used in advanced scene editing, material decomposition, and high quality view interpolation, all running at interactive rates in triangle-based renderers (rasterizers and path tracers). Project website: https://nvlabs.github.io/nvdiffrec/ .Comment: Project website: https://nvlabs.github.io/nvdiffrec

Physically Based Rendering Techniques to Visualize Thin-Film Smoothed Particle Hydrodynamics Fluid Simulations

This thesis introduces a methodology and workflow I developed to visualize smoothed hydrodynamic particle based simulations for the research paper ’Thin-Film Smoothed Particle Hydrodynamics Fluid’ (2021), that I co-authored. I introduce a physically based rendering model which allows point cloud simulation data representing thin film fluids and bubbles to be rendered in a photorealistic manner. This includes simulating the optic phenomenon of thin-film interference and rendering the resulting iridescent patterns. The key to the model lies in the implementation of a physically based surface shader that accounts for the interference of infinitely many internally reflected rays in its bidirectional surface scattering function. By simulating the effect of interference on rays reflected off the surface of a thin-film as a component of a surface shader, I am able to obtain photorealistic renderings of bubbles and thin-films. This enables us to visualize complex vortical swirls and turbulent surface flows on oscillating and deforming surfaces in a physically accurate and visually evocative manner