809 research outputs found
MeshAdv: Adversarial Meshes for Visual Recognition
Highly expressive models such as deep neural networks (DNNs) have been widely
applied to various applications. However, recent studies show that DNNs are
vulnerable to adversarial examples, which are carefully crafted inputs aiming
to mislead the predictions. Currently, the majority of these studies have
focused on perturbation added to image pixels, while such manipulation is not
physically realistic. Some works have tried to overcome this limitation by
attaching printable 2D patches or painting patterns onto surfaces, but can be
potentially defended because 3D shape features are intact. In this paper, we
propose meshAdv to generate "adversarial 3D meshes" from objects that have rich
shape features but minimal textural variation. To manipulate the shape or
texture of the objects, we make use of a differentiable renderer to compute
accurate shading on the shape and propagate the gradient. Extensive experiments
show that the generated 3D meshes are effective in attacking both classifiers
and object detectors. We evaluate the attack under different viewpoints. In
addition, we design a pipeline to perform black-box attack on a photorealistic
renderer with unknown rendering parameters.Comment: Published in IEEE CVPR201
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
Exposure Render: An Interactive Photo-Realistic Volume Rendering Framework
The field of volume visualization has undergone rapid development during the past years, both due to advances in suitable computing hardware and due to the increasing availability of large volume datasets. Recent work has focused on increasing the visual realism in Direct Volume Rendering (DVR) by integrating a number of visually plausible but often effect-specific rendering techniques, for instance modeling of light occlusion and depth of field. Besides yielding more attractive renderings, especially the more realistic lighting has a positive effect on perceptual tasks. Although these new rendering techniques yield impressive results, they exhibit limitations in terms of their exibility and their performance. Monte Carlo ray tracing (MCRT), coupled with physically based light transport, is the de-facto standard for synthesizing highly realistic images in the graphics domain, although usually not from volumetric data. Due to the stochastic sampling of MCRT algorithms, numerous effects can be achieved in a relatively straight-forward fashion. For this reason, we have developed a practical framework that applies MCRT techniques also to direct volume rendering (DVR). With this work, we demonstrate that a host of realistic effects, including physically based lighting, can be simulated in a generic and flexible fashion, leading to interactive DVR with improved realism. In the hope that this improved approach to DVR will see more use in practice, we have made available our framework under a permissive open source license
A directional occlusion shading model for interactive direct volume rendering
Volumetric rendering is widely used to examine 3D scalar fields from CT/MRI scanners and numerical simulation datasets. One key aspect of volumetric rendering is the ability to provide perceptual cues to aid in understanding structure contained in the data. While shading models that reproduce natural lighting conditions have been shown to better convey depth information and spatial relationships, they traditionally require considerable (pre)computation. In this paper, a shading model for interactive direct volume rendering is proposed that provides perceptual cues similar to those of ambient occlusion, for both solid and transparent surface-like features. An image space occlusion factor is derived from the radiative transport equation based on a specialized phase function. The method does not rely on any precomputation and thus allows for interactive explorations of volumetric data sets via on-the-fly editing of the shading model parameters or (multi-dimensional) transfer functions while modifications to the volume via clipping planes are incorporated into the resulting occlusion-based shading
Mobile ray-tracing
Dissertação de mestrado em Computer ScienceThe technological advances and the massification of information technologies have
allowed a huge and positive proliferation of the number of libraries and APIs. This large
offer has made life easier for programmers in general, because they easily find a library,
free or commercial, that helps them solve the daily challenges they have at hand.
One area of information technology where libraries are critical is in Computer Graphics,
due to the wide range of rendering techniques it offers. One of these techniques is ray
tracing. Ray tracing allows to simulate natural electromagnetic phenomena such as the
path of light and mechanical phenomena such as the propagation of sound. Similarly, it also
allows to simulate technologies developed by men, like Wi-Fi networks. These simulations
can have a spectacular realism and accuracy, at the expense of a very high computational
cost.
The constant evolution of technology allowed to leverage and massify new areas, such as
mobile devices. Devices today are increasingly faster, replacing and often complementing
tasks that were previously performed only on computers or on dedicated hardware.
However, the number of image rendering libraries available for mobile devices is still very
scarce, and no ray tracing based image rendering library has been able to assert itself on
these devices. This dissertation aims to explore the possibilities and limitations of using
mobile devices to execute rendering algorithms that use ray tracing, such as progressive
path tracing. Its main goal is to provide a rendering library for mobile devices based on ray
tracing.Os avanços tecnológicos e a massificação das tecnologias de informação permitiu uma
enorme e positiva proliferação do número de bibliotecas e APIs. Esta maior oferta permitiu
facilitar a vida dos programadores em geral, porque facilmente encontram uma biblioteca,
gratuita ou comercial, que os ajudam a resolver os desafios diários que têm em mãos.
Uma área das tecnologias de informação onde as bibliotecas são fundamentais é na
Computação Gráfica, devido à panóplia de métodos de renderização que oferece. Um
destes métodos é o ray tracing. O ray tracing permite simular fenómenos eletromagnéticos
naturais como os percursos da luz e fenómenos mecânicos como a propagação do som. Da
mesma forma também permite simular tecnologias desenvolvidas pelo homem, como por
exemplo redes Wi-Fi. Estas simulações podem ter um realismo e precisão impressionantes,
porém têm um custo computacional muito elevado.
A constante evolução da tecnologia permitiu alavancar e massificar novas áreas, como
os dispositivos móveis. Os dispositivos são hoje cada vez mais rápidos e cada vez
mais substituem e/ou complementam tarefas que anteriormente eram apenas realizadas
em computadores ou em hardware dedicado. Porém, o número de bibliotecas para
renderização de imagens disponÃveis para dispositivos móveis é ainda muito reduzido
e nenhuma biblioteca de renderização de imagens baseada em ray tracing conseguiu
afirmar-se nestes dispositivos. Esta dissertação tem como objetivo explorar possibilidades
e limitações da utilização de dispositivos móveis para a execução de algoritmos de
renderização que utilizem ray tracing, como por exemplo, o path tracing progressivo. O
objetivo principal é disponibilizar uma biblioteca de renderização para dispositivos móveis
baseada em ray tracing
BlockGAN: Learning 3D Object-aware Scene Representations from Unlabelled Images
We present BlockGAN, an image generative model that learns object-aware 3D
scene representations directly from unlabelled 2D images. Current work on scene
representation learning either ignores scene background or treats the whole
scene as one object. Meanwhile, work that considers scene compositionality
treats scene objects only as image patches or 2D layers with alpha maps.
Inspired by the computer graphics pipeline, we design BlockGAN to learn to
first generate 3D features of background and foreground objects, then combine
them into 3D features for the wholes cene, and finally render them into
realistic images. This allows BlockGAN to reason over occlusion and interaction
between objects' appearance, such as shadow and lighting, and provides control
over each object's 3D pose and identity, while maintaining image realism.
BlockGAN is trained end-to-end, using only unlabelled single images, without
the need for 3D geometry, pose labels, object masks, or multiple views of the
same scene. Our experiments show that using explicit 3D features to represent
objects allows BlockGAN to learn disentangled representations both in terms of
objects (foreground and background) and their properties (pose and identity).Comment: For project page, see https://www.monkeyoverflow.com/#/blockgan/
Accepted to Conference on Neural Information Processing Systemsm, NeurIPS
202
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