Sergio Orts Escolano
Sergio Orts-Escolano is a Senior Staff Research Scientist at Google (Zürich), where he leads research on egocentric perception and 3D digital humans for Android XR . His current focus integrates real-time wearable tracking, digital humans, neural rendering, and scalable synthetic data flywheels that train next-generation spatial computing and multimodal foundation models.
Throughout his career across academia and industrial research labs, Sergio has co-created foundational systems in 3D capture and tele-immersion—including seminal breakthroughs like Holoportation and Fusion4D—while delivering high-impact machine learning algorithms directly into consumer platforms such as Google Camera, Google Photos, and Android XR
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Text to 3D Object Generation for Scalable Room Assembly
Sonia Laguna
Alberto García García
Marie-Julie Rakotosaona
Stylianos Moschoglou
Leonhard Helminger
2025
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Modern machine learning models for scene understanding, such as depth estimation and object tracking, rely on large, high-quality datasets that mimic real-world deployment scenarios. To address data scarcity, an end-to-end system for synthetic data generation for scalable, high-quality, and customizable 3D indoor scenes. By integrating text-to-image and multi-view diffusion models with NeRF-based meshing, this system generates high-fidelity 3D assets from text prompts and incorporates them into pre-defined floor plans using a rendering tool, Blender. By incorporating novel loss functions and training strategies into prior existing methods, or method supports on-demand object generation, bridging the domain gap between synthetic and real-world data. This system advances synthetic data’s role in addressing machine learning training limitations, enabling more robust and generalizable models for real-world applications.
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Cafca: High-quality Novel View Synthesis of Expressive Faces from Casual Few-shot Captures
Marcel Bühler
Simon Li
Erroll Wood
Leonhard Helminger
Xu Chen
Tanmay Shah
Daoye Wang
Stephan Garbin
Otmar Hilliges
Dmitry Lagun
Jérémy Riviere
Paulo Gotardo
Thabo Beeler
Abhi Meka
2024
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Volumetric modeling and neural radiance field representations have revolutionized 3D face capture and photorealistic novel view synthesis. However, these methods often require hundreds of multi-view input images and are thus inapplicable to cases with less than a handful of inputs. We present a novel volumetric prior on human faces that allows for high-fidelity expressive face modeling from as few as three input views captured in the wild. Our key insight is that an implicit prior trained on synthetic data alone can generalize to extremely challenging real-world identities and expressions and render novel views with fine idiosyncratic details like wrinkles and eyelashes. We leverage a 3D Morphable Face Model to synthesize a large training set, rendering each identity with different expressions, hair, clothing, and other assets. We then train a conditional Neural Radiance Field prior on this synthetic dataset and, at inference time, fine-tune the model on a very sparse set of real images of a single subject. On average, the fine-tuning requires only three inputs to cross the synthetic-to-real domain gap. The resulting personalized 3D model reconstructs strong idiosyncratic facial expressions and outperforms the state-of-the-art in high-quality novel view synthesis of faces from sparse inputs in terms of perceptual and photo-metric quality.
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Rapsai: Accelerating Machine Learning Prototyping of Multimedia Applications through Visual Programming
Na Li
Jing Jin
Michelle Carney
Scott Joseph Miles
Maria Kleiner
Xiuxiu Yuan
Anuva Kulkarni
Xingyu “Bruce” Liu
Ahmed K Sabie
Abhishek Kar
Ping Yu
Ram Iyengar
Alex Olwal
Proceedings of the 2023 CHI Conference on Human Factors in Computing Systems (CHI), ACM
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In recent years, there has been a proliferation of multimedia applications that leverage machine learning (ML) for interactive experiences. Prototyping ML-based applications is, however, still challenging, given complex workflows that are not ideal for design and experimentation. To better understand these challenges, we conducted a formative study with seven ML practitioners to gather insights about common ML evaluation workflows.
This study helped us derive six design goals, which informed Rapsai, a visual programming platform for rapid and iterative development of end-to-end ML-based multimedia applications. Rapsai is based on a node-graph editor to facilitate interactive characterization and visualization of ML model performance. Rapsai streamlines end-to-end prototyping with interactive data augmentation and model comparison capabilities in its no-coding environment. Our evaluation of Rapsai in four real-world case studies (N=15) suggests that practitioners can accelerate their workflow, make more informed decisions, analyze strengths and weaknesses, and holistically evaluate model behavior with real-world input.
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LitNeRF: Intrinsic Radiance Decomposition for High-Quality View Synthesis and Relighting of Faces
Marcel Bühler
Simon Li
Daoye Wang
Delio Vicini
Jérémy Riviere
Paulo Gotardo
Thabo Beeler
Abhi Meka
2023
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High-fidelity, photorealistic 3D capture of a human face is a long-standing problem in computer graphics – the complex material of skin, intricate geometry of hair, and fine scale textural details make it challenging. Traditional techniques rely on very large and expensive capture rigs to reconstruct explicit mesh geometry and appearance maps, and are limited by the accuracy of hand-crafted reflectance models. More recent volumetric methods (e.g., NeRFs) have enabled view-synthesis and sometimes relighting by learning an implicit representation of the density and reflectance basis, but suffer from artifacts and blurriness due to the inherent ambiguities in volumetric modeling. These problems are further exacerbated when capturing with few cameras and light sources. We present a novel technique for high-quality capture of a human face for 3D view synthesis and relighting using a sparse, compact capture rig consisting of 15 cameras and 15 lights. Our method combines a neural volumetric representation with traditional mesh reconstruction from multiview stereo. The proxy geometry allows us to anchor the 3D density field to prevent artifacts and guide the disentanglement of intrinsic radiance components of the face appearance such as diffuse and specular reflectance, and incident radiance (shadowing) fields. Our hybrid representation significantly improves the state-of-the-art quality for arbitrarily dense renders of a face from desired camera viewpoint as well as environmental, directional, and near-field lighting.
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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
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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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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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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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Deep Relightable Textures: Volumetric Performance Capture with Neural Rendering
Abhi Meka
Christian Haene
Peter Barnum
Philip Davidson
Daniel Erickson
Jonathan Taylor
Sofien Bouaziz
Wan-Chun Alex Ma
Ryan Overbeck
Thabo Beeler
Paul Debevec
Shahram Izadi
Christian Theobalt
Christoph Rhemann
SIGGRAPH Asia and TOG (2020)
Preview abstract
The increasing demand for 3D content in augmented and virtual reality has motivated the development of volumetric performance capture systems such as the Light Stage. Recent advances are pushing free viewpoint relightable videos of dynamic human performances closer to photorealistic quality. However, despite significant efforts, these sophisticated systems are limited by reconstruction and rendering algorithms which do not fully model complex 3D structures and higher order light transport effects such as global illumination and sub-surface scattering. In this paper, we propose a system that combines traditional geometric pipelines with a neural rendering scheme to generate photorealistic renderings of dynamic performances under desired viewpoint and lighting. Our system leverages deep neural networks that model the classical rendering process to learn implicit features that represent the view-dependent appearance of the subject independent of the geometry layout, allowing for generalization to unseen subject poses and even novel subject identity. Detailed experiments and comparisons demonstrate the efficacy and versatility of our method to generate high-quality results, significantly outperforming the existing state-of-the-art solutions.
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Computational stereo has reached a high level of accuracy, but degrades in the presence of occlusions, repeated textures, and correspondence errors along edges. We present a novel approach based on neural networks for depth estimation that combines stereo from dual cameras with stereo from a dual-pixel sensor, which is increasingly common on consumer cameras. Our network uses a novel architecture to fuse these two sources of information and can overcome the above-mentioned
limitations of pure binocular stereo matching. Our method provides a dense depth map with sharp edges, which is crucial for computational photography applications like synthetic shallow-depth-of-field or 3D Photos. Additionally, we avoid the inherent ambiguity due to the aperture problem in stereo cameras by designing the stereo baseline to be orthogonal to the dual-pixel baseline. We present experiments and comparisons with state-of-the-art approaches to show that our method offers a substantial improvement over previous works.
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The Relightables: Volumetric Performance Capture of Humans with Realistic Relighting
Kaiwen Guo
Peter Lincoln
Philip Davidson
Xueming Yu
Matt Whalen
Geoff Harvey
Jason Dourgarian
Danhang Tang
Anastasia Tkach
Emily Cooper
Mingsong Dou
Graham Fyffe
Christoph Rhemann
Jonathan Taylor
Paul Debevec
Shahram Izadi
SIGGRAPH Asia (2019) (to appear)
Preview abstract
We present ''The Relightables'', a volumetric capture system for photorealistic and high quality relightable full-body performance capture. While significant progress has been made on volumetric capture systems, focusing on 3D geometric reconstruction with high resolution textures, much less work has been done to recover photometric properties needed for relighting. Results from such systems lack high-frequency details and the subject's shading is prebaked into the texture. In contrast, a large body of work has addressed relightable acquisition for image-based approaches, which photograph the subject under a set of basis lighting conditions and recombine the images to show the subject as they would appear in a target lighting environment. However, to date, these approaches have not been adapted for use in the context of a high-resolution volumetric capture system. Our method combines this ability to realistically relight humans for arbitrary environments, with the benefits of free-viewpoint volumetric capture and new levels of geometric accuracy for dynamic performances. Our subjects are recorded inside a custom geodesic sphere outfitted with 331 custom color LED lights, an array of high-resolution cameras, and a set of custom high-resolution depth sensors. Our system innovates in multiple areas: First, we designed a novel active depth sensor to capture 12.4MP depth maps, which we describe in detail. Second, we show how to design a hybrid geometric and machine learning reconstruction pipeline to process the high resolution input and output a volumetric video. Third, we generate temporally consistent reflectance maps for dynamic performers by leveraging the information contained in two alternating color gradient illumination images acquired at 60Hz. Multiple experiments, comparisons, and applications show that The Relightables significantly improves upon the level of realism in placing volumetrically captured human performances into arbitrary CG scenes.
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