Browsing by Author "Lin, Yiming"

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    AirLens: Multi-Level Visual Exploration of Air Quality Evolution in Urban Agglomerations
    (The Eurographics Association and John Wiley & Sons Ltd., 2022) Qu, Dezhan; Lv, Cheng; Lin, Yiming; Zhang, Huijie; Wang, Rong; Borgo, Rita; Marai, G. Elisabeta; Schreck, Tobias
    The precise prevention and control of air pollution is a great challenge faced by environmental experts in recent years. Understanding the air quality evolution in the urban agglomeration is important for coordinated control of air pollution. However, the complex pollutant interactions between different cities lead to the collaborative evolution of air quality. The existing statistical and machine learning methods cannot well support the comprehensive analysis of the dynamic air quality evolution. In this study, we propose AirLens, an interactive visual analytics system that can help domain experts explore and understand the air quality evolution in the urban agglomeration from multiple levels and multiple aspects. To facilitate the cognition of the complex multivariate spatiotemporal data, we first propose a multi-run clustering strategy with a novel glyph design for summarizing and understanding the typical pollutant patterns effectively. On this basis, the system supports the multi-level exploration of air quality evolution, namely, the overall level, stage level and detail level. Frequent pattern mining, city community extraction and useful filters are integrated into the system for discovering significant information comprehensively. The case study and positive feedback from domain experts demonstrate the effectiveness and usability of AirLens.
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    Deep Shape and SVBRDF Estimation using Smartphone Multi-lens Imaging
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Fan, Chongrui; Lin, Yiming; Ghosh, Abhijeet; Chaine, Raphaëlle; Deng, Zhigang; Kim, Min H.
    We present a deep neural network-based method that acquires high-quality shape and spatially varying reflectance of 3D objects using smartphone multi-lens imaging. Our method acquires two images simultaneously using a zoom lens and a wide angle lens of a smartphone under either natural illumination or phone flash conditions, effectively functioning like a single-shot method. Unlike traditional multi-view stereo methods which require sufficient differences in viewpoint and only estimate depth at a certain coarse scale, our method estimates fine-scale depth by utilising an optical-flow field extracted from subtle baseline and perspective due to different optics in the two images captured simultaneously. We further guide the SVBRDF estimation using the estimated depth, resulting in superior results compared to existing single-shot methods.
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    On-Site Example-Based Material Appearance Acquisition
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Lin, Yiming; Peers, Pieter; Ghosh, Abhijeet; Boubekeur, Tamy and Sen, Pradeep
    We present a novel example-based material appearance modeling method suitable for rapid digital content creation. Our method only requires a single HDR photograph of a homogeneous isotropic dielectric exemplar object under known natural illumination. While conventional methods for appearance modeling require prior knowledge on the object shape, our method does not, nor does it recover the shape explicitly, greatly simplifying on-site appearance acquisition to a lightweight photography process suited for non-expert users. As our central contribution, we propose a shape-agnostic BRDF estimation procedure based on binary RGB profile matching.We also model the appearance of materials exhibiting a regular or stationary texture-like appearance, by synthesizing appropriate mesostructure from the same input HDR photograph and a mesostructure exemplar with (roughly) similar features. We believe our lightweight method for on-site shape-agnostic appearance acquisition presents a suitable alternative for a variety of applications that require plausible ''rapid-appearance-modeling''.
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    Polarization-imaging Surface Reflectometry using Near-field Display
    (The Eurographics Association, 2022) Nogue, Emilie; Lin, Yiming; Ghosh, Abhijeet; Ghosh, Abhijeet; Wei, Li-Yi
    We present a practical method for measurement of spatially varying isotropic surface reflectance of planar samples using a combination of single-view polarization imaging and near-field display illumination. Unlike previous works that have required multiview imaging or more complex polarization measurements, our method requires only three linear polarizer measurements from a single viewpoint for estimating diffuse and specular albedo and spatially varying specular roughness. We obtain highquality estimate of the surface normal with two additional polarized measurements under a gradient illumination pattern. Our approach enables high-quality renderings of planar surfaces while reducing measurements to a near-optimal number for the estimated SVBRDF parameters.
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    Practical Acquisition of Shape and Plausible Appearance of Reflective and Translucent Objects
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Lin, Arvin; Lin, Yiming; Ghosh, Abhijeet; Ritschel, Tobias; Weidlich, Andrea
    We present a practical method for acquisition of shape and plausible appearance of reflective and translucent objects for realistic rendering and relighting applications. Such objects are extremely challenging to scan with existing capture setups, and have previously required complex lightstage hardware emitting continuous illumination. We instead employ a practical capture setup consisting of a set of desktop LCD screens to illuminate such objects with piece-wise continuous illumination for acquisition. We employ phase-shifted sinusoidal illumination for novel estimation of high quality photometric normals and transmission vector along with diffuse-specular separated reflectance/transmission maps for realistic relighting. We further employ neural in-painting to fill gaps in our measurements caused by gaps in screen illumination, and a novel NeuS-based neural rendering that combines these shape and reflectance maps acquired from multiple viewpoints for high-quality 3D surface geometry reconstruction along with plausible realistic rendering of complex light transport in such objects.