Search Results

Now showing 1 - 5 of 5
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    Structure-preserving Style Transfer
    (The Eurographics Association, 2019) Calvo, Santiago; Serrano, Ana; Gutierrez, Diego; Masia, Belen; Casas, Dan and Jarabo, Adrián
    Transferring different artistic styles to images while preserving their content is a difficult image processing task. Since the seminal deep learning approach of Gatys et al. [GEB16], many recent works have proposed different approaches for performing this task. However, most of them share one major limitation: a trade-off between how much the target style is transferred, and how much the content of the original source image is preserved [GEB16, GEB*17, HB17, LPSB17]. In this work, we present a structure-preserving approach for style transfer that builds on top of the approach proposed by Gatys et al. Our approach allows to preserve regions of fine detail by lowering the intensity of the style transfer for such regions, while still conveying the desired style in the overall appearance of the image. We propose to use a quad-tree image subdivision, and then apply the style transfer operation differently for different subdivision levels. Effectively, this leads to a more intense style transfer in large flat regions, while the content is better preserved in areas with fine structure and details. Our approach can be easily applied to different style transfer approaches as a post-processing step.
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    Bidirectional Rendering of Polarized Light Transport
    (The Eurographics Association, 2016) Jarabo, Adrian; Gutierrez, Diego; Alejandro Garcia-Alonso and Belen Masia
    On the foundations of many rendering algorithm is the symmetry between the path traversed by light and its adjoint from the camera. However, several effects, including polarization or fluorescence, break that symmetry and are defined only on the direction of light. This complicates the applicability of bidirectional methods, that exploit the symmetry for effective rendering light transport. In this work we focus on how to include polarization within a bidirectional rendering algorithm. For that, we generalize the path integral to support the constraints imposed by non-symmetric light transport. Based on this theoretical framework, we propose modifications on two bidirectional methods, namely bidirectional path tracing and photon mapping, extending them to support polarization.
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    Transient Photon Beams
    (The Eurographics Association, 2017) Marco, Julio; Jarosz, Wojciech; Gutierrez, Diego; Jarabo, Adrian; Fco. Javier Melero and Nuria Pelechano
    Recent advances on transient imaging and their applications have opened the necessity of forward models that allow precise generation and analysis of time-resolved light transport data. However, traditional steady-state rendering techniques are not suitable for computing transient light transport due to the aggravation of the inherent Monte Carlo variance over time. These issues are specially problematic in participating media, which demand high number of samples to achieve noise-free solutions. We address this problem by presenting the first photon-based method for transient rendering of participating media that performs density estimations on time-resolved precomputed photon maps. We first introduce the transient integral form of the radiative transfer equation into the computer graphics community, including transient delays on the scattering events. Based on this formulation we leverage the high density and parameterized continuity provided by photon beams algorithms to present a new transient method that allows to significantly mitigate variance and efficiently render participating media effects in transient state.
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    A Physically-Based Spatio-Temporal Sky Model
    (The Eurographics Association, 2018) Guimera, David; Gutierrez, Diego; Jarabo, Adrián; García-Fernández, Ignacio and Ureña, Carlos
    In this work we present a physically-based optical model of the atmosphere, that takes into account the seasonal and geographic variation of its composition. Based on data from the atmospheric science literature, we build a highly detailed the composition of the atmosphere, and how it varies depending on the position of the observer, or the time of the year. Then, based on precise measurements of the optical properties of the components of the atmosphere, we map our model into a radiative model, which can be rendered in any existing volumetric renderer. We demonstrate our model in multispectral renders of daylight sky-domes, showing the changes in the appearance occurring when varying the season or location of the observer.
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    Improved Intuitive Appearance Editing based on Soft PCA
    (The Eurographics Association, 2017) Malpica, Sandra; Barrio, Miguel; Gutierrez, Diego; Serrano, Ana; Masia, Belen; Fco. Javier Melero and Nuria Pelechano
    During the last few years, many different techniques for measuring material appearance have arisen. These advances have allowed the creation of large public datasets, and new methods for editing BRDFs of captured appearance have been proposed. However, these methods lack intuitiveness and are hard to use for novice users. In order to overcome these limitations, Serrano et al. [SGM 16] recently proposed an intuitive space for editing captured appearance. They make use of a representation of the BRDF based on a combination of principal components (PCA) to reduce dimensionality, and then map these components to perceptual attributes. This PCA representation is biased towards specular materials and fails to represent very diffuse BRDFs, therefore producing unpleasant artifacts when editing. In this paper, we build on top of their work and propose to use two separate PCA bases for representing specular and diffuse BRDFs, and map each of these bases to the perceptual attributes. This allows us to avoid artifacts when editing towards diffuse BRDFs. We then propose a new method for effectively navigate between both bases while editing based on a new measurement of the specularity of measured materials. Finally, we integrate our proposed method in an intuitive BRDF editing framework and show how some of the limitations of the previous model have been overcomed with our representation. Moreover, our new measure of specularity can be used on any measured BRDF, as it is not limited only to MERL BRDFs [MPBM03].