Distributed high-fidelity graphics using P2P

In the field of three-dimensional computer graphics, rendering refers to the process of generating images of a scene from a particular viewpoint. There are many different ways to do this, from the highly interactive real-time rendering methods to the more photorealistic and computationally intensive methods. This work is concerned with Physically Based Rendering (PBR), a class of rendering algorithms capable of achieving a very high level of realism. This is achievable thanks to physically accurate modelling of the way light interacts with objects in a scene, together with the use of accurately modelled materials and physical quantities.peer-reviewe

Renderizado fotorrealista con Irradiance Caching

Treballs Finals de Grau d'Enginyeria Informàtica, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2021, Director: Ricardo Jorge Rodrigues Sepúlveda Marques[en] Nowadays, we are surrounded by computer generated images. Some examples may be: Furniture catalogs, video games, cinema... These images have evolved into what today is called Photorealistic Rendering, which is one of the most important topics in Computer Graphics. This project implements one photorealistic rendering algorithm called Irradiance Caching and compares it with another one called Path Tracing. Furthermore, it will showcase the differences between both of them and compare their execution times as well. The main goal is to program an Irradiance Caching algorithm in the ray tracer more efficient than the Path Tracing algorithm, maintaining the image quality as much as possible

Practical photon mapping in hardware

Photon mapping is a popular global illumination algorithm that can reproduce a wide range of visual effects including indirect illumination, color bleeding and caustics on complex diffuse, glossy, and specular surfaces modeled using arbitrary geometric primitives. However, the large amount of computation and tremendous amount of memory bandwidth, terabytes per second, required makes photon mapping prohibitively expensive for interactive applications. In this dissertation I present three techniques that work together to reduce the bandwidth requirements of photon mapping by over an order of magnitude. These are combined in a hardware architecture that can provide interactive performance on moderately-sized indirectly-illuminated scenes using a pre-computed photon map. 1. The computations of the naive photon map algorithm are efficiently reordered, generating exactly the same image, but with an order of magnitude less bandwidth due to an easily cacheable sequence of memory accesses. 2. The irradiance caching algorithm is modified to allow fine-grain parallel execution by removing the sequential dependency between pixels. The bandwidth requirements of scenes with diffuse surfaces and low geometric complexity is reduced by an additional 40% or more. 3. Generating final gather rays in proportion to both the incident radiance and the reflectance functions requires fewer final gather rays for images of the same quality. Combined Importance Sampling is simple to implement, cheap to compute, compatible with query reordering, and can reduce bandwidth requirements by an order of magnitude. Functional simulation of a practical and scalable hardware architecture based on these three techniques shows that an implementation that would fit within a host workstation will achieve interactive rates. This architecture is therefore a candidate for the next generation of graphics hardware

Radiance Caching for Efficient Global Illumination Computation

In this paper we present a ray tracing based method for accelerated global illumination computation in scenes with low-frequency glossy BRDFs. The method is based on sparse sampling, caching, and interpolating radiance on glossy surfaces. In particular we extend the irradiance caching scheme of \cite{ward88ray} to cache and interpolate directional incoming radiance instead of irradiance. The incoming radiance at a point is represented by a vector of coefficients with respect to a spherical or hemispherical basis. The surfaces suitable for interpolation are selected automatically according to the glossiness of their BRDF. We also propose a novel method for computing translational radiance gradient at a point

Intuitive and Accurate Material Appearance Design and Editing

Creating and editing high-quality materials for photorealistic rendering can be a difficult task due to the diversity and complexity of material appearance. Material design is the process by which artists specify the reflectance properties of a surface, such as its diffuse color and specular roughness. Even with the support of commercial software packages, material design can be a time-consuming trial-and-error task due to the counter-intuitive nature of the complex reflectance models. Moreover, many material design tasks require the physical realization of virtually designed materials as the final step, which makes the process even more challenging due to rendering artifacts and the limitations of fabrication. In this dissertation, we propose a series of studies and novel techniques to improve the intuitiveness and accuracy of material design and editing. Our goal is to understand how humans visually perceive materials, simplify user interaction in the design process and, and improve the accuracy of the physical fabrication of designs. Our first work focuses on understanding the perceptual dimensions for measured material data. We build a perceptual space based on a low-dimensional reflectance manifold that is computed from crowd-sourced data using a multi-dimensional scaling model. Our analysis shows the proposed perceptual space is consistent with the physical interpretation of the measured data. We also put forward a new material editing interface that takes advantage of the proposed perceptual space. We visualize each dimension of the manifold to help users understand how it changes the material appearance. Our second work investigates the relationship between translucency and glossiness in material perception. We conduct two human subject studies to test if subsurface scattering impacts gloss perception and examine how the shape of an object influences this perception. Based on our results, we discuss why it is necessary to include transparent and translucent media for future research in gloss perception and material design. Our third work addresses user interaction in the material design system. We present a novel Augmented Reality (AR) material design prototype, which allows users to visualize their designs against a real environment and lighting. We believe introducing AR technology can make the design process more intuitive and improve the authenticity of the results for both novice and experienced users. To test this assumption, we conduct a user study to compare our prototype with the traditional material design system with gray-scale background and synthetic lighting. The results demonstrate that with the help of AR techniques, users perform better in terms of objectively measured accuracy and time and they are subjectively more satisfied with their results. Finally, our last work turns to the challenge presented by the physical realization of designed materials. We propose a learning-based solution to map the virtually designed appearance to a meso-scale geometry that can be easily fabricated. Essentially, this is a fitting problem, but compared with previous solutions, our method can provide the fabrication recipe with higher reconstruction accuracy for a large fitting gamut. We demonstrate the efficacy of our solution by comparing the reconstructions with existing solutions and comparing fabrication results with the original design. We also provide an application of bi-scale material editing using the proposed method

A Final Reconstruction Approach for a Unified Global Illumination Algorithm

International audienceIn the past twenty years, many algorithms have been proposed to compute global illumination in synthetic scenes. Typically, such approaches can deal with specific lighting configurations, but often have difficulties with others. In this article, we present a final reconstruction step for a novel unified approach to global illumination, that automatically detects different types of light transfer and uses the appropriate method in a closely-integrated manner. With our approach, we can deal with difficult lighting configurations such as indirect nondiffuse illumination. The first step of this algorithm consists in a view-independent solution based on hierarchical radiosity with clustering, integrated with particle tracing. This first pass results in solutions containing directional effects such as caustics, which can be interactively rendered. The second step consists of a view-dependent final reconstruction that uses all existing information to compute higher quality, ray-traced images