Sean Fanello
I am a Research Scientist and Manager at Google, where I am leading efforts to solve real-world human perception tasks, often relying on performance capture and neural rendering to train deep learning models that generalize to in-the-wild applications.
My research interests include: 3D performance capture, photo realistic rendering, neural rendering, relighting, viewpoint synthesis.
Previously, I was a Senior Scientist and a Founding Team Member at perceptiveIO, Inc., where I developed computer vision and machine learning algorithms for 3D sensing, visual recognition and human-computer interaction.
Prior to that, I was a Post-Doc Researcher in the Interactive 3D Technologies (I3D) group at Microsoft Research Redmond where I substantially contributed to the Hololens 3D sensing capabilities. I was also one of the main contributors for the Holoportation project.
I obtained my PhD in Robotics, Cognition and Interaction Technologies at the Italian Institute of Technology in collaboration with the University of Genoa in 2013. During my PhD I developed computer vision and machine learning techniques for the iCub humanoid robot.
In 2010 I completed my Master’s Degree in Computer Engineering at Sapienza University of Rome, with a specialization in Artificial Intelligence and Pattern Recognition.
Personal website: http://seanfanello.it
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Sandwiched Compression: Repurposing Standard Codecs with Neural Network Wrappers
Phil A. Chou
Berivan Isik
Hugues Hoppe
Danhang Tang
Jonathan Taylor
Philip Davidson
arXiv:2402.05887(2024)
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We propose sandwiching standard image and video codecs between pre- and post-processing neural networks. The networks are jointly trained through a differentiable codec proxy to minimize a given rate-distortion loss. This sandwich architecture not only improves the standard codec’s performance on its intended content, it can effectively adapt the codec to other types of image/video content and to other distortion measures. Essentially, the sandwich learns to transmit “neural code images” that optimize overall rate-distortion performance even when the overall problem is well outside the scope of the codec’s design. Through a variety of examples, we apply the sandwich architecture to sources with different numbers of channels, higher resolution, higher dynamic range, and perceptual distortion measures. The results demonstrate substantial improvements (up to 9 dB gains or up to 3 adaptations. We derive VQ equivalents for the sandwich, establish optimality properties, and design differentiable codec proxies approximating current standard codecs. We further analyze model complexity, visual quality under perceptual metrics, as well as sandwich configurations that offer interesting potentials in image/video compression and streaming.
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Multi-Camera Lighting Estimation for Photorealistic Front-Facing Mobile AR
Yiqin Zhao
Tian Guo
Association for Computing Machinery, New York, NY, USA(2023), 68–73
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Lighting estimation plays an important role in virtual object composition, including mobile augmented reality (AR) applications. Prior work often targets recovering lighting from the physical environment to support photorealistic AR rendering. Because the common workflow is to use a backward-facing camera to capture the overlay of the physical world and virtual objects, we refer to this usage pattern as backward-facing AR. However, existing methods often fall short of supporting emerging front-facing virtual try-on applications
where a mobile user leverages a front-facing camera to explore the effect of various products, e.g., glasses or hats, of different styles. This lack of support can be attributed to the unique challenges of obtaining 360◦ HDR environment maps, an ideal format of lighting representation, from the front-facing camera. In this paper, we propose to leverage a dual-camera streaming setup (front and backward-facing), to perform multi-view lighting estimation. Our approach results in improved rendering quality and visually coherent AR try-on experiences. Our contributions include energy conserving data capturing, high-quality environment map generation, and parametric directional light estimation.
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Learning Personalized High Quality Volumetric Head Avatars from Monocular RGB Videos
Ziqian Bai
Danhang "Danny" Tang
Di Qiu
Abhimitra Meka
Mingsong Dou
Ping Tan
Thabo Beeler
2023 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), IEEE
Preview abstract
We propose a method to learn a high-quality implicit 3D head avatar from a monocular RGB video captured in the wild. The learnt avatar is driven by a parametric face model to achieve user-controlled facial expressions and head poses. Our hybrid pipeline combines the geometry prior and dynamic tracking of a 3DMM with a neural radiance field to achieve fine-grained control and photorealism. To reduce over-smoothing and improve out-of-model expressions synthesis, we propose to predict local features anchored on the 3DMM geometry. These learnt features are driven by 3DMM deformation and interpolated in 3D space to yield the volumetric radiance at a designated query point. We further show that using a Convolutional Neural Network in the UV space is critical in incorporating spatial context and producing representative local features. Extensive experiments show that we are able to reconstruct high-quality avatars, with more accurate expression-dependent details, good generalization to out-of-training expressions, and quantitatively superior renderings compared to other state-of-the-art approaches.
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Sandwiched Image Compression: Increasing the resolution and dynamic range of standard codecs
Phil Chou
Hugues Hoppe
Danhang "Danny" Tang
Philip Davidson
2022 Picture Coding Symposium (PCS), IEEE (to appear)
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Given a standard image codec, we compress images that may have higher resolution and/or higher bit depth than allowed in the codec's specifications, by sandwiching the standard codec between a neural pre-processor (before the standard encoder) and a neural post-processor (after the standard decoder). Using a differentiable proxy for the the standard codec, we design the neural pre- and post-processors to transport the high resolution (super-resolution, SR) or high bit depth (high dynamic range, HDR) images as lower resolution and lower bit depth images. The neural processors accomplish this with spatially coded modulation, which acts as watermarks to preserve the important image detail during compression. Experiments show that compared to conventional methods of transmitting high resolution or high bit depth through lower resolution or lower bit depth codecs, our sandwich architecture gains ~9 dB for SR images and ~3 dB for HDR images at the same rate over large test sets. We also observe significant gains in visual quality.
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Neural Light Transport for Relighting and View Synthesis
Xiuming Zhang
Yun-Ta Tsai
Tiancheng Sun
Tianfan Xue
Philip Davidson
Christoph Rhemann
Paul Debevec
Ravi Ramamoorthi
ACM Transactions on Graphics, 40(2021)
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The light transport (LT) of a scene describes how it appears under different lighting and viewing directions, and complete knowledge of a scene's LT enables the synthesis of novel views under arbitrary lighting. In this paper, we focus on image-based LT acquisition, primarily for human bodies within a light stage setup. We propose a semi-parametric approach to learn a neural representation of LT that is embedded in the space of a texture atlas of known geometric properties, and model all non-diffuse and global LT as residuals added to a physically-accurate diffuse base rendering. In particular, we show how to fuse previously seen observations of illuminants and views to synthesize a new image of the same scene under a desired lighting condition from a chosen viewpoint. This strategy allows the network to learn complex material effects (such as subsurface scattering) and global illumination, while guaranteeing the physical correctness of the diffuse LT (such as hard shadows). With this learned LT, one can relight the scene photorealistically with a directional light or an HDRI map, synthesize novel views with view-dependent effects, or do both simultaneously, all in a unified framework using a set of sparse, previously seen observations. Qualitative and quantitative experiments demonstrate that our neural LT (NLT) outperforms state-of-the-art solutions for relighting and view synthesis, without separate treatment for both problems that prior work requires.
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HumanGPS: Geodesic PreServing Feature for Dense Human Correspondence
Danhang "Danny" Tang
Mingsong Dou
Kaiwen Guo
Cem Keskin
Sofien Bouaziz
Ping Tan
Computer Vision and Pattern Recognition 2021(2021), pp. 8
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In this paper, we address the problem of building dense correspondences between human images under arbitrary camera viewpoints and body poses. Prior art either assumes small motion between frames or relies on local descriptors, which cannot handle large motion or visually ambiguous body parts, e.g. left v.s. right hand. In contrast, we propose a deep learning framework that maps each pixel to a feature space, where the feature distances reflect the geodesic distances among pixels as if they were projected onto the surface of a 3D human scan. To this end, we introduce novel loss functions to push features apart according to their geodesic distances on the surface. Without any semantic annotation, the proposed embeddings automatically learn to differentiate visually similar parts and align different subjects into an unified feature space. Extensive experiments show that the learned embeddings can produce accurate correspondences between images with remarkable generalization capabilities on both intra and inter subjects.
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Sandwiched Image Compression: Wrapping Neural Networks Around a Standard Codec
Phil Chou
Hugues Hoppe
Danhang "Danny" Tang
Philip Davidson
2021 IEEE International Conference on Image Processing (ICIP), IEEE, Anchorage, Alaska, pp. 3757-3761
Preview abstract
We sandwich a standard image codec between two neural networks: a preprocessor that outputs neural codes, and a postprocessor that reconstructs the image. The neural codes are compressed as ordinary images by the standard codec. Using differentiable proxies for both rate and distortion, we develop a rate-distortion optimization framework that trains the networks to generate neural codes that are efficiently compressible as images. This architecture not only improves rate-distortion performance for ordinary RGB images, but also enables efficient compression of alternative image types (such as normal maps of computer graphics) using standard image codecs. Results demonstrate the effectiveness and flexibility of neural processing in mapping a variety of input data modalities to the rigid structure of standard codecs. A surprising result is that the rate-distortion-optimized neural processing seamlessly learns to transport color images using a single-channel (grayscale) codec.
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Total Relighting: Learning to Relight Portraits for Background Replacement
Christian Haene
Sofien Bouaziz
Christoph Rhemann
Paul Debevec
SIGGRAPH and TOG(2021)
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We propose a novel system for portrait relighting and background replacement, which maintains high-frequency boundary details and accurately synthesizes the subject’s appearance as lit by novel illumination, thereby producing realistic composite images for any desired scene. Our technique includes foreground estimation via alpha matting, relighting, and compositing. We demonstrate that each of these stages can be tackled in a sequential pipeline without the use of priors (e.g. known background or known illumination) and with no specialized acquisition techniques, using only a single RGB portrait image and a novel, target HDR lighting environment as inputs. We train our model using relit portraits of subjects captured in a light stage computational illumination system, which records multiple lighting conditions, high quality geometry, and accurate alpha mattes. To perform realistic relighting for compositing, we introduce a novel per-pixel lighting representation in a deep learning framework, which explicitly models the diffuse and the specular components of appearance, producing relit portraits with convincingly rendered non-Lambertian effects like specular highlights. Multiple experiments and comparisons show the effectiveness of the proposed approach when applied to in-the-wild images.
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Multiresolution Deep Implicit Functions for 3D Shape Representation
Zhang Chen
Kyle Genova
Sofien Bouaziz
Christian Haene
Cem Keskin
Danhang "Danny" Tang
ICCV(2021)
Preview abstract
We introduce Multiresolution Deep Implicit Functions (MDIF), a hierarchical representation that can recover fine details, while being able to perform more global operations such as shape completion.
Our model represents a complex 3D shape with a hierarchy of latent grids, which can be decoded into different resolutions. Training is performed in an encoder-decoder manner, while the decoder-only optimization is supported during inference, hence can better generalize to novel objects, especially when performing shape completion. To the best of our knowledge, MDIF is the first model that can at the same time (1) reconstruct local detail; (2) perform decoder-only inference; (3) fulfill shape reconstruction and completion. We demonstrate superior performance against prior arts in our experiments.
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Light Stage Super-Resolution: Continuous High-Frequency Relighting
Tiancheng Sun
Zexiang Xu
Xiuming Zhang
Christoph Rhemann
Paul Debevec
Yun-Ta Tsai
Ravi Ramamoorthi
SIGGRAPH Asia and TOG(2020)
Preview abstract
The light stage has been widely used in computer graphics for the past two decades, primarily to enable the relighting of human faces. By capturing the appearance of the human subject under different light sources, one obtains the light transport matrix of that subject, which enables image-based relighting in novel environments. However, due to the finite number of lights in the stage, the light transport matrix only represents a sparse sampling on the entire sphere. As a consequence, relighting the subject with a point light or a directional source that does not coincide exactly with one of the lights in the stage requires interpolation and resampling the images corresponding to nearby lights, and this leads to ghosting shadows, aliased specularities, and other artifacts. To ameliorate these artifacts and produce better results under arbitrary high-frequency lighting, this paper proposes a learning-based solution for the "super-resolution" of scans of human faces taken from a light stage. Given an arbitrary "query" light direction, our method aggregates the captured images corresponding to neighboring lights in the stage, and uses a neural network to synthesize a rendering of the face that appears to be illuminated by a "virtual" light source at the query location. This neural network must circumvent the inherent aliasing and regularity of the light stage data that was used for training, which we accomplish through the use of regularized traditional interpolation methods within our network. Our learned model is able to produce renderings for arbitrary light directions that exhibit realistic shadows and specular highlights, and is able to generalize across a wide variety of subjects. Our super-resolution approach enables more accurate renderings of human subjects under detailed environment maps, or the construction of simpler light stages that contain fewer light sources while still yielding comparable quality renderings as light stages with more densely sampled lights.
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