Gaspard Zoss

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25ranked-venue papers
4as first author
20since 2021 · last 2025
0000-0002-0022-8203ORCID · verified

Domains — the database's venue-derived domains; a paper can count in several

Graphics, computer vision, multimedia, augmented reality and games · 25 · 4 first-author · 20 since 2021Artificial intelligence and machine learning · 6 · 6 since 2021Human-computer interaction and ubiquitous computing · 1 · 1 since 2021
YearPublicationVenuePosition
2025 Monocular Facial Appearance Capture in the Wild
abstract
We present a new method for reconstructing the appearance properties of human faces from a lightweight capture procedure in an unconstrained environment. Our method recovers the surface geometry, diffuse albedo, specular intensity and specular roughness from a monocular video containing a simple head rotation in-the-wild. Notably, we make no simplifying assumptions on the environment lighting, and we explicitly take visibility and occlusions into account. As a result, our method can produce facial appearance maps that approach the fidelity of studio-based multi-view captures, but with a far easier and cheaper procedure.
Yingyan Xu, Kate Gadola, Prashanth Chandran, Sebastian Weiss, Markus Gross 0001, Gaspard Zoss, Derek Bradley
ICCV6
2025 Multimodal Conditional 3D Face Geometry Generation
abstract
We present a new method for multimodal conditional 3D face geometry generation that allows user-friendly control over the output identity and expression via a number of different conditioning signals. Within a single model, we demonstrate 3D faces generated from artistic sketches, portrait photos, Canny edges, FLAME face model parameters, 2D face landmarks, or text prompts. Our approach is based on a diffusion process that generates 3D geometry in a 2D parameterized UV domain. Geometry generation passes each conditioning signal through a set of cross-attention layers (IP-Adapter), one set for each user-defined conditioning signal. The result is an easy-to-use 3D face generation tool that produces topology-consistent, high-quality geometry with fine-grain user control. • We present a new method for 3D face geometry generation from 6 different types of conditionings (prompts) within a single model. • We propose a comprehensive solution for training such a method from scratch, with 3D geometry data augmentations and by representing 3D geometry as position maps to better fit existing diffusion pipelines. • We show that our method supports face generation with expressions, sketch-based editing for 3D face design, stochastic variations of details conditioned on low resolution FLAME faces, generalization to in-the-wild data and dynamic face generation from videos.
Christopher Otto, Prashanth Chandran, Sebastian Weiss, Markus Gross 0001, Gaspard Zoss, Derek Bradley
Comput. Graph.5
2024 Anatomically Constrained Implicit Face Models
abstract
Coordinate based implicit neural representations have gained rapid popularity in recent years as they have been successfully used in image, geometry and scene modeling tasks. In this work, we present a novel use case for such implicit representations in the context of learning anatomi-cally constrained face models. Actor specific anatomically constrainedface models are the state of the art in bothfacial performance capture and performance retargeting. Despite their practical success, these anatomical models are slow to evaluate and often require extensive data capture to be built. We propose the anatomical implicit face model; an ensem-ble of implicit neural networks that jointly learn to model the facial anatomy and the skin surface with high-fidelity, and can readily be used as a drop in replacement to con-ventional blendshape models. Given an arbitrary set of skin surface meshes of an actor and only a neutral shape with estimated skull and jaw bones, our method can recover a dense anatomical substructure which constrains every point on the facial surface. We demonstrate the usefulness of our approach in several tasks ranging from shape fitting, shape editing, and performance retargeting.
Prashanth Chandran, Gaspard Zoss
CVPR2
2024 Artist-Friendly Relightable and Animatable Neural Heads
abstract
An increasingly common approach for creating photo-realistic digital avatars is through the use of volumetric neural fields. The original neural radiance field (NeRF) allowed for impressive novel view synthesis of static heads when trained on a set of multi-view images, and follow up methods showed that these neural representations can be extended to dynamic avatars. Recently, new variants also surpassed the usual drawback of baked-in illumination in neural representations, showing that static neural avatars can be relit in any environment. In this work we simultaneously tackle both the motion and illumination problem, proposing a new method for relightable and animatable neural heads. Our method builds on a proven dynamic avatar approach based on a mixture of volumetric primitives, combined with a recently-proposed lightweight hardware setup for relightable neural fields, and includes a novel architecture that allows relighting dynamic neural avatars performing unseen expressions in any environment, even with nearfield illumination and viewpoints.
Yingyan Xu, Prashanth Chandran, Sebastian Weiss, Markus Gross 0001, Gaspard Zoss, Derek Bradley
CVPR5
2024 Infinite 3D Landmarks: Improving Continuous 2D Facial Landmark Detection
abstract
Abstract In this paper, we examine three important issues in the practical use of state‐of‐the‐art facial landmark detectors and show how a combination of specific architectural modifications can directly improve their accuracy and temporal stability. First, many facial landmark detectors require a face normalization step as a pre‐process, often accomplished by a separately trained neural network that crops and resizes the face in the input image. There is no guarantee that this pre‐trained network performs optimal face normalization for the task of landmark detection. Thus, we instead analyse the use of a spatial transformer network that is trained alongside the landmark detector in an unsupervised manner, jointly learning an optimal face normalization and landmark detection by a single neural network. Second, we show that modifying the output head of the landmark predictor to infer landmarks in a canonical 3D space rather than directly in 2D can further improve accuracy. To convert the predicted 3D landmarks into screen‐space, we additionally predict the camera intrinsics and head pose from the input image. As a side benefit, this allows to predict the 3D face shape from a given image only using 2D landmarks as supervision, which is useful in determining landmark visibility among other things. Third, when training a landmark detector on multiple datasets at the same time, annotation inconsistencies across datasets forces the network to produce a sub‐optimal average. We propose to add a semantic correction network to address this issue. This additional lightweight neural network is trained alongside the landmark detector, without requiring any additional supervision. While the insights of this paper can be applied to most common landmark detectors, we specifically target a recently proposed continuous 2D landmark detector to demonstrate how each of our additions leads to meaningful improvements over the state‐of‐the‐art on standard benchmarks.
Prashanth Chandran, Gaspard Zoss, Paulo F. U. Gotardo, Derek Bradley
Comput. Graph. Forum2
2024 Stylize My Wrinkles: Bridging the Gap from Simulation to Reality
abstract
Abstract Modeling realistic human skin with pores and wrinkles down to the milli‐ and micrometer resolution is a challenging task. Prior work showed that such micro geometry can be efficiently generated through simulation methods, or in specialized cases via 3D scanning of real skin. Simulation methods allow to highly customize the wrinkles on the face, but can lead to a synthetic look. Scanning methods can lead to a more organic look for the micro details, however these methods are only applicable to small skin patches due to the required image resolution. In this work we aim to overcome the gap between synthetic simulation and real skin scanning, by proposing a method that can be applied to large skin regions (e.g. an entire face) with the controllability of simulation and the organic look of real micro details. Our method is based on style transfer at its core, where we use scanned displacement maps of real skin patches as style images and displacement maps from an artist‐friendly simulation method as content images. We build a library of displacement maps as style images by employing a simplified scanning setup that can capture high‐resolution patches of real skin. To create the content component for the style transfer and to facilitate parameter‐tuning for the simulation, we design a library of preset parameter values depicting different skin types, and present a new method to fit the simulation parameters to scanned skin patches. This allows fully‐automatic parameter generation, interpolation and stylization across entire faces. We evaluate our method by generating realistic skin micro details for various subjects of different ages and genders, and demonstrate that our approach achieves a more organic and natural look than simulation alone.
Sebastian Weiss, Jackson Stanhope, Prashanth Chandran, Gaspard Zoss, Derek Bradley
Comput. Graph. Forum4
2024 Learning a Generalized Physical Face Model From Data
abstract
Physically-based simulation is a powerful approach for 3D facial animation as the resulting deformations are governed by physical constraints, allowing to easily resolve self-collisions, respond to external forces and perform realistic anatomy edits. Today's methods are data-driven, where the actuations for finite elements are inferred from captured skin geometry. Unfortunately, these approaches have not been widely adopted due to the complexity of initializing the material space and learning the deformation model for each character separately, which often requires a skilled artist followed by lengthy network training. In this work, we aim to make physics-based facial animation more accessible by proposing a generalized physical face model that we learn from a large 3D face dataset. Once trained, our model can be quickly fit to any unseen identity and produce a ready-to-animate physical face model automatically. Fitting is as easy as providing a single 3D face scan, or even a single face image. After fitting, we offer intuitive animation controls, as well as the ability to retarget animations across characters. All the while, the resulting animations allow for physical effects like collision avoidance, gravity, paralysis, bone reshaping and more.
Lingchen Yang, Gaspard Zoss, Prashanth Chandran, Markus Gross 0001, Barbara Solenthaler, Eftychios Sifakis, Derek Bradley
ACM Trans. Graph.2
2023 Continuous Landmark Detection with 3D Queries
abstract
Neural networks for facial landmark detection are notoriously limited to a fixed set of landmarks in a dedicated layout, which must be specified at training time. Dedicated datasets must also be hand-annotated with the corresponding landmark configuration for training. We propose the first facial landmark detection network that can predict continuous, unlimited landmarks, allowing to specify the number and location of the desired landmarks at inference time. Our method combines a simple image feature extractor with a queried landmark predictor, and the user can specify any continuous query points relative to a 3D template face mesh as input. As it is not tied to a fixed set of landmarks, our method is able to leverage all pre-existing 2D landmark datasets for training, even if they have inconsistent landmark configurations. As a result, we present a very powerful facial landmark detector that can be trained once, and can be used readily for numerous applications like 3D face reconstruction, arbitrary face segmentation, and is even compatible with helmeted mounted cameras, and therefore could vastly simplify face tracking workflows for media and entertainment applications.
Prashanth Chandran, Gaspard Zoss, Paulo F. U. Gotardo, Derek Bradley
CVPR2
2023 ReNeRF: Relightable Neural Radiance Fields with Nearfield Lighting
abstract
Recent work on radiance fields and volumetric inverse rendering (e.g., NeRFs) has provided excellent results in building data-driven models of real scenes for novel view synthesis with high photorealism. While full control over viewpoint is achieved, scene lighting is typically "baked" into the model and cannot be changed; other methods only capture limited variation in lighting or make restrictive assumptions about the captured scene. These limitations prevent the application on arbitrary materials and novel 3D environments with complex, distinct lighting. In this paper, we target the application scenario of capturing high-fidelity assets for neural relighting in controlled studio conditions, but without requiring a dense light stage. Instead, we leverage a small number of area lights commonly used in photogrammetry. We propose ReNeRF, a relightable radiance field model based on the intuitive and powerful approach of image-based relighting, which implicitly captures global light transport (for arbitrary objects) without complex, error-prone simulations. Thus, our new method is simple and provides full control over viewpoint and lighting, without simplistic assumptions about how light interacts with the scene. In addition, ReNeRF does not rely on the usual assumption of distant lighting – during training, we explicitly account for the distance between 3D points in the volume and point samples on the light sources. Thus, at test time, we achieve better generalization to novel, continuous lighting directions, including nearfield lighting effects.
Yingyan Xu, Gaspard Zoss, Prashanth Chandran, Markus Gross 0001, Derek Bradley, Paulo F. U. Gotardo
ICCV2
2023 An Implicit Physical Face Model Driven by Expression and Style
abstract
3D facial animation is often produced by manipulating facial deformation models (or rigs), that are traditionally parameterized by expression controls. A key component that is usually overlooked is expression “style", as in, how a particular expression is performed. Although it is common to define a semantic basis of expressions that characters can perform, most characters perform each expression in their own style. To date, style is usually entangled with the expression, and it is not possible to transfer the style of one character to another when considering facial animation. We present a new face model, based on a data-driven implicit neural physics model, that can be driven by both expression and style separately. At the core, we present a framework for learning implicit physics-based actuations for multiple subjects simultaneously, trained on a few arbitrary performance capture sequences from a small set of identities. Once trained, our method allows generalized physics-based facial animation for any of the trained identities, extending to unseen performances. Furthermore, it grants control over the animation style, enabling style transfer from one character to another or blending styles of different characters. Lastly, as a physics-based model, it is capable of synthesizing physical effects, such as collision handling, setting our method apart from conventional approaches.
Lingchen Yang, Gaspard Zoss, Prashanth Chandran, Paulo F. U. Gotardo, Markus Gross 0001, Barbara Solenthaler, Eftychios Sifakis, Derek Bradley
SIGGRAPH Asia2
2023 A Perceptual Shape Loss for Monocular 3D Face Reconstruction
abstract
Abstract Monocular 3D face reconstruction is a wide‐spread topic, and existing approaches tackle the problem either through fast neural network inference or offline iterative reconstruction of face geometry. In either case carefully‐designed energy functions are minimized, commonly including loss terms like a photometric loss, a landmark reprojection loss, and others. In this work we propose a new loss function for monocular face capture, inspired by how humans would perceive the quality of a 3D face reconstruction given a particular image. It is widely known that shading provides a strong indicator for 3D shape in the human visual system. As such, our new ‘perceptual’ shape loss aims to judge the quality of a 3D face estimate using only shading cues. Our loss is implemented as a discriminator‐style neural network that takes an input face image and a shaded render of the geometry estimate, and then predicts a score that perceptually evaluates how well the shaded render matches the given image. This ‘critic’ network operates on the RGB image and geometry render alone, without requiring an estimate of the albedo or illumination in the scene. Furthermore, our loss operates entirely in image space and is thus agnostic to mesh topology. We show how our new perceptual shape loss can be combined with traditional energy terms for monocular 3D face optimization and deep neural network regression, improving upon current state‐of‐the‐art results.
Christopher Otto, Prashanth Chandran, Gaspard Zoss, Markus Gross 0001, Paulo F. U. Gotardo, Derek Bradley
Comput. Graph. Forum3
2023 Graph-Based Synthesis for Skin Micro Wrinkles
abstract
Abstract We present a novel graph‐based simulation approach for generating micro wrinkle geometry on human skin, which can easily scale up to the micro‐meter range and millions of wrinkles. The simulation first samples pores on the skin and treats them as nodes in a graph. These nodes are then connected and the resulting edges become candidate wrinkles. An iterative optimization inspired by pedestrian trail formation is then used to assign weights to those edges, i.e., to carve out the wrinkles. Finally, we convert the graph to a detailed skin displacement map using novel shape functions implemented in graphics shaders. Our simulation and displacement map creation steps expose fine controls over the appearance at real‐time framerates suitable for interactive exploration and design. We demonstrate the effectiveness of the generated wrinkles by enhancing state‐of‐art 3D reconstructions of real human subjects with simulated micro wrinkles, and furthermore propose an artist‐driven design flow for adding micro wrinkles to fictional characters.
Sebastian Weiss, J. Moulin, Prashanth Chandran, Gaspard Zoss, Paulo F. U. Gotardo, Derek Bradley
Comput. Graph. Forum4
2022 Shape Transformers: Topology-Independent 3D Shape Models Using Transformers
abstract
Abstract Parametric 3D shape models are heavily utilized in computer graphics and vision applications to provide priors on the observed variability of an object's geometry (e.g., for faces). Original models were linear and operated on the entire shape at once. They were later enhanced to provide localized control on different shape parts separately. In deep shape models, nonlinearity was introduced via a sequence of fully‐connected layers and activation functions, and locality was introduced in recent models that use mesh convolution networks. As common limitations, these models often dictate, in one way or another, the allowed extent of spatial correlations and also require that a fixed mesh topology be specified ahead of time. To overcome these limitations, we present Shape Transformers, a new nonlinear parametric 3D shape model based on transformer architectures. A key benefit of this new model comes from using the transformer's self‐attention mechanism to automatically learn nonlinear spatial correlations for a class of 3D shapes. This is in contrast to global models that correlate everything and local models that dictate the correlation extent. Our transformer 3D shape autoencoder is a better alternative to mesh convolution models, which require specially‐crafted convolution, and down/up‐sampling operators that can be difficult to design. Our model is also topologically independent: it can be trained once and then evaluated on any mesh topology, unlike most previous methods. We demonstrate the application of our model to different datasets, including 3D faces, 3D hand shapes and full human bodies. Our experiments demonstrate the strong potential of our Shape Transformer model in several applications in computer graphics and vision.
Prashanth Chandran, Gaspard Zoss, Markus Gross 0001, Paulo F. U. Gotardo, Derek Bradley
Comput. Graph. Forum2
2022 Facial Animation with Disentangled Identity and Motion using Transformers
abstract
Abstract We propose a 3D+time framework for modeling dynamic sequences of 3D facial shapes, representing realistic non‐rigid motion during a performance. Our work extends neural 3D morphable models by learning a motion manifold using a transformer architecture. More specifically, we derive a novel transformer‐based autoencoder that can model and synthesize 3D geometry sequences of arbitrary length. This transformer naturally determines frame‐to‐frame correlations required to represent the motion manifold, via the internal self‐attention mechanism. Furthermore, our method disentangles the constant facial identity from the time‐varying facial expressions in a performance, using two separate codes to represent neutral identity and the performance itself within separate latent subspaces. Thus, the model represents identity‐agnostic performances that can be paired with an arbitrary new identity code and fed through our new identity‐modulated performance decoder; the result is a sequence of 3D meshes for the performance with the desired identity and temporal length. We demonstrate how our disentangled motion model has natural applications in performance synthesis, performance retargeting, key‐frame interpolation and completion of missing data, performance denoising and retiming, and other potential applications that include full 3D body modeling.
Prashanth Chandran, Gaspard Zoss, Markus Gross 0001, Paulo F. U. Gotardo, Derek Bradley
Comput. Graph. Forum2
2022 Learning Dynamic 3D Geometry and Texture for Video Face Swapping
abstract
Abstract Face swapping is the process of applying a source actor's appearance to a target actor's performance in a video. This is a challenging visual effect that has seen increasing demand in film and television production. Recent work has shown that data‐driven methods based on deep learning can produce compelling effects at production quality in a fraction of the time required for a traditional 3D pipeline. However, the dominant approach operates only on 2D imagery without reference to the underlying facial geometry or texture, resulting in poor generalization under novel viewpoints and little artistic control. Methods that do incorporate geometry rely on pre‐learned facial priors that do not adapt well to particular geometric features of the source and target faces. We approach the problem of face swapping from the perspective of learning simultaneous convolutional facial autoencoders for the source and target identities, using a shared encoder network with identity‐specific decoders. The key novelty in our approach is that each decoder first lifts the latent code into a 3D representation, comprising a dynamic face texture and a deformable 3D face shape, before projecting this 3D face back onto the input image using a differentiable renderer. The coupled autoencoders are trained only on videos of the source and target identities, without requiring 3D supervision. By leveraging the learned 3D geometry and texture, our method achieves face swapping with higher quality than when using off‐the‐shelf monocular 3D face reconstruction, and overall lower FID score than state‐of‐the‐art 2D methods. Furthermore, our 3D representation allows for efficient artistic control over the result, which can be hard to achieve with existing 2D approaches.
Christopher Otto, Jacek Naruniec, Leonhard Helminger, Thomas Etterlin, Graziana Mignone, Prashanth Chandran, Gaspard Zoss, Christopher Schroers, Markus Gross 0001, Paulo F. U. Gotardo, Derek Bradley, Romann M. Weber
Comput. Graph. Forum7
2022 Facial hair tracking for high fidelity performance capture
abstract
Facial hair is a largely overlooked topic in facial performance capture. Most production pipelines in the entertainment industry do not have a way to automatically capture facial hair or track the skin underneath it. Thus, actors are asked to shave clean before face capture, which is very often undesirable. Capturing the geometry of individual facial hairs is very challenging, and their presence makes it harder to capture the deforming shape of the underlying skin surface. Some attempts have already been made at automating this task, but only for static faces with relatively sparse 3D hair reconstructions. In particular, current methods lack the temporal correspondence needed when capturing a sequence of video frames depicting facial performance. The problem of robustly tracking the skin underneath also remains unaddressed. In this paper, we propose the first multiview reconstruction pipeline that tracks both the dense 3D facial hair, as well as the underlying 3D skin for entire performances. Our method operates with standard setups for face photogrammetry, without requiring dense camera arrays. For a given capture subject, our algorithm first reconstructs a dense, high-quality neutral 3D facial hairstyle by registering sparser hair reconstructions over multiple frames that depict a neutral face under quasi-rigid motion. This custom-built, reference facial hairstyle is then tracked throughout a variety of changing facial expressions in a captured performance, and the result is used to constrain the tracking of the 3D skin surface underneath. We demonstrate the proposed capture pipeline on a variety of different facial hairstyles and lengths, ranging from sparse and short to dense full-beards.
Sebastian Winberg, Gaspard Zoss, Prashanth Chandran, Paulo F. U. Gotardo, Derek Bradley
ACM Trans. Graph.2
2022 Implicit neural representation for physics-driven actuated soft bodies
abstract
Active soft bodies can affect their shape through an internal actuation mechanism that induces a deformation. Similar to recent work, this paper utilizes a differentiable, quasi-static, and physics-based simulation layer to optimize for actuation signals parameterized by neural networks. Our key contribution is a general and implicit formulation to control active soft bodies by defining a function that enables a continuous mapping from a spatial point in the material space to the actuation value. This property allows us to capture the signal's dominant frequencies, making the method discretization agnostic and widely applicable. We extend our implicit model to mandible kinematics for the particular case of facial animation and show that we can reliably reproduce facial expressions captured with high-quality capture systems. We apply the method to volumetric soft bodies, human poses, and facial expressions, demonstrating artist-friendly properties, such as simple control over the latent space and resolution invariance at test time.
Lingchen Yang, Byungsoo Kim 0001, Gaspard Zoss, Baran Gözcü, Markus Gross 0001, Barbara Solenthaler
ACM Trans. Graph.3
2022 Production-Ready Face Re-Aging for Visual Effects
abstract
Photorealistic digital re-aging of faces in video is becoming increasingly common in entertainment and advertising. But the predominant 2D painting workflow often requires frame-by-frame manual work that can take days to accomplish, even by skilled artists. Although research on facial image re-aging has attempted to automate and solve this problem, current techniques are of little practical use as they typically suffer from facial identity loss, poor resolution, and unstable results across subsequent video frames. In this paper, we present the first practical, fully-automatic and production-ready method for re-aging faces in video images. Our first key insight is in addressing the problem of collecting longitudinal training data for learning to re-age faces over extended periods of time, a task that is nearly impossible to accomplish for a large number of real people. We show how such a longitudinal dataset can be constructed by leveraging the current state-of-the-art in facial re-aging that, although failing on real images, does provide photoreal re-aging results on synthetic faces. Our second key insight is then to leverage such synthetic data and formulate facial re-aging as a practical image-to-image translation task that can be performed by training a well-understood U-Net architecture, without the need for more complex network designs. We demonstrate how the simple U-Net, surprisingly, allows us to advance the state of the art for re-aging real faces on video, with unprecedented temporal stability and preservation of facial identity across variable expressions, viewpoints, and lighting conditions. Finally, our new face re-aging network (FRAN) incorporates simple and intuitive mechanisms that provides artists with localized control and creative freedom to direct and fine-tune the re-aging effect, a feature that is largely important in real production pipelines and often overlooked in related research work.
Gaspard Zoss, Prashanth Chandran, Eftychios Sifakis, Markus Gross 0001, Paulo F. U. Gotardo, Derek Bradley
ACM Trans. Graph.1
2021 Adaptive Convolutions for Structure-Aware Style Transfer
abstract
Style transfer between images is an artistic application of CNNs, where the ‘style’ of one image is transferred onto another image while preserving the latter’s content. The state of the art in neural style transfer is based on Adaptive Instance Normalization (AdaIN), a technique that transfers the statistical properties of style features to a content image, and can transfer a large number of styles in real time. However, AdaIN is a global operation; thus local geometric structures in the style image are often ignored during the transfer. We propose Adaptive Convolutions (AdaConv), a generic extension of AdaIN, to allow for the simultaneous transfer of both statistical and structural styles in real time. Apart from style transfer, our method can also be readily extended to style-based image generation, and other tasks where AdaIN has already been adopted.
Prashanth Chandran, Gaspard Zoss, Paulo F. U. Gotardo, Markus Gross 0001, Derek Bradley
CVPR2
2021 Rendering with style: combining traditional and neural approaches for high-quality face rendering
abstract
For several decades, researchers have been advancing techniques for creating and rendering 3D digital faces, where a lot of the effort has gone into geometry and appearance capture, modeling and rendering techniques. This body of research work has largely focused on facial skin, with much less attention devoted to peripheral components like hair, eyes and the interior of the mouth. As a result, even with the best technology for facial capture and rendering, in most high-end productions a lot of artist time is still spent modeling the missing components and fine-tuning the rendering parameters to combine everything into photo-real digital renders. In this work we propose to combine incomplete, high-quality renderings showing only facial skin with recent methods for neural rendering of faces, in order to automatically and seamlessly create photo-realistic full-head portrait renders from captured data without the need for artist intervention. Our method begins with traditional face rendering, where the skin is rendered with the desired appearance, expression, viewpoint, and illumination. These skin renders are then projected into the latent space of a pre-trained neural network that can generate arbitrary photo-real face images (StyleGAN2). The result is a sequence of realistic face images that match the identity and appearance of the 3D character at the skin level, but is completed naturally with synthesized hair, eyes, inner mouth and surroundings. Notably, we present the first method for multi-frame consistent projection into this latent space, allowing photo-realistic rendering and preservation of the identity of the digital human over an animated performance sequence, which can depict different expressions, lighting conditions and viewpoints. Our method can be used in new face rendering pipelines and, importantly, in other deep learning applications that require large amounts of realistic training data with ground-truth 3D geometry, appearance maps, lighting, and viewpoint.
Prashanth Chandran, Sebastian Winberg, Gaspard Zoss, Jérémy Riviere, Markus Gross 0001, Paulo F. U. Gotardo, Derek Bradley
ACM Trans. Graph.3
2020 Fast Nonlinear Least Squares Optimization of Large-Scale Semi-Sparse Problems
abstract
Abstract Many problems in computer graphics and vision can be formulated as a nonlinear least squares optimization problem, for which numerous off‐the‐shelf solvers are readily available. Depending on the structure of the problem, however, existing solvers may be more or less suitable, and in some cases the solution comes at the cost of lengthy convergence times. One such case is semi‐sparse optimization problems, emerging for example in localized facial performance reconstruction, where the nonlinear least squares problem can be composed of hundreds of thousands of cost functions, each one involving many of the optimization parameters. While such problems can be solved with existing solvers, the computation time can severely hinder the applicability of these methods. We introduce a novel iterative solver for nonlinear least squares optimization of large‐scale semi‐sparse problems. We use the nonlinear Levenberg‐Marquardt method to locally linearize the problem in parallel, based on its first‐order approximation. Then, we decompose the linear problem in small blocks, using the local Schur complement, leading to a more compact linear system without loss of information. The resulting system is dense but its size is small enough to be solved using a parallel direct method in a short amount of time. The main benefit we get by using such an approach is that the overall optimization process is entirely parallel and scalable, making it suitable to be mapped onto graphics hardware (GPU). By using our minimizer, results are obtained up to one order of magnitude faster than other existing solvers, without sacrificing the generality and the accuracy of the model. We provide a detailed analysis of our approach and validate our results with the application of performance‐based facial capture using a recently‐proposed anatomical local face deformation model.
Marco Fratarcangeli, Derek Bradley, Aurel Gruber, Gaspard Zoss, Thabo Beeler
Comput. Graph. Forum4
2020 Interactive Sculpting of Digital Faces Using an Anatomical Modeling Paradigm
abstract
Abstract Digitally sculpting 3D human faces is a very challenging task. It typically requires either 1) highly‐skilled artists using complex software packages for high quality results, or 2) highly‐constrained simple interfaces for consumer‐level avatar creation, such as in game engines. We propose a novel interactive method for the creation of digital faces that is simple and intuitive to use, even for novice users, while consistently producing plausible 3D face geometry, and allowing editing freedom beyond traditional video game avatar creation. At the core of our system lies a specialized anatomical local face model (ALM), which is constructed from a dataset of several hundred 3D face scans. User edits are propagated to constraints for an optimization of our data‐driven ALM model, ensuring the resulting face remains plausible even for simple edits like clicking and dragging surface points. We show how several natural interaction methods can be implemented in our framework, including direct control of the surface, indirect control of semantic features like age, ethnicity, gender, and BMI, as well as indirect control through manipulating the underlying bony structures. The result is a simple new method for creating digital human faces, for artists and novice users alike. Our method is attractive for low‐budget VFX and animation productions, and our anatomical modeling paradigm can complement traditional game engine avatar design packages.
Aurel Gruber, Marco Fratarcangeli, Gaspard Zoss, Roman Cattaneo, Thabo Beeler, Markus Gross 0001, Derek Bradley
Comput. Graph. Forum3
2020 Data-driven extraction and composition of secondary dynamics in facial performance capture
abstract
Performance capture of expressive subjects, particularly facial performances acquired with high spatial resolution, will inevitably incorporate some fraction of motion that is due to inertial effects and dynamic overshoot due to ballistic motion. This is true in most natural capture environments where the actor is able to move freely during their performance, rather than being tethered to a fixed position. Normally these secondary dynamic effects are unwanted, as the captured facial performance is often retargeted to different head motion, and sometimes to completely different characters, and in both cases the captured dynamic effects should be removed and new secondary effects should be added. This paper advances the hypothesis that for a highly constrained elastic medium such as the human face, these secondary inertial effects are predominantly due to the motion of the underlying bony structures (cranium and mandible). Our work aims to compute and characterize the difference between the captured dynamic facial performance, and a speculative quasistatic variant of the same motion should the inertial effects have been absent. This is used to either subtract parasitic secondary dynamics that resulted from unintentional motion during capture, or compose such effects on top of a quasistatic performance to simulate a new dynamic motion of the actor's body and skull, either artist-prescribed or acquired via motion capture. We propose a data-driven technique that comprises complementary removal and synthesis networks for secondary dynamics in facial performance capture. We show how such a system can be effectively trained from a collection of acquired dynamic deformations under varying expressions where the actor induces rigid head motion from walking and running, as well as forced oscillatory body motion in a controlled setting by external actuators.
Gaspard Zoss, Eftychios Sifakis, Markus Gross 0001, Thabo Beeler, Derek Bradley
ACM Trans. Graph.1
2019 Accurate markerless jaw tracking for facial performance capture
abstract
We present the first method to accurately track the invisible jaw based solely on the visible skin surface, without the need for any markers or augmentation of the actor. As such, the method can readily be integrated with off-the-shelf facial performance capture systems. The core idea is to learn a non-linear mapping from the skin deformation to the underlying jaw motion on a dataset where ground-truth jaw poses have been acquired, and then to retarget the mapping to new subjects. Solving for the jaw pose plays a central role in visual effects pipelines, since accurate jaw motion is required when retargeting to fantasy characters and for physical simulation. Currently, this task is performed mostly manually to achieve the desired level of accuracy, and the presented method has the potential to fully automate this labour intense and error prone process.
Gaspard Zoss, Thabo Beeler, Markus Gross 0001, Derek Bradley
ACM Trans. Graph.1
2018 An empirical rig for jaw animation
abstract
In computer graphics the motion of the jaw is commonly modelled by up-down and left-right rotation around a fixed pivot plus a forward-backward translation, yielding a three dimensional rig that is highly suited for intuitive artistic control. The anatomical motion of the jaw is, however, much more complex since the joints that connect the jaw to the skull exhibit both rotational and translational components. In reality the jaw does not move in a three dimensional subspace but on a constrained manifold in six dimensions. We analyze this manifold in the context of computer animation and show how the manifold can be parameterized with three degrees of freedom, providing a novel jaw rig that preserves the intuitive control while providing more accurate jaw positioning. The chosen parameterization furthermore places anatomically correct limits on the motion, preventing the rig from entering physiologically infeasible poses. Our new jaw rig is empirically designed from accurate capture data, and we provide a simple method to retarget the rig to new characters, both human and fantasy.
Gaspard Zoss, Derek Bradley, Pascal Bérard, Thabo Beeler
ACM Trans. Graph.1