174 research outputs found
Towards Racially Unbiased Skin Tone Estimation via Scene Disambiguation
Virtual facial avatars will play an increasingly important role in immersive
communication, games and the metaverse, and it is therefore critical that they
be inclusive. This requires accurate recovery of the appearance, represented by
albedo, regardless of age, sex, or ethnicity. While significant progress has
been made on estimating 3D facial geometry, albedo estimation has received less
attention. The task is fundamentally ambiguous because the observed color is a
function of albedo and lighting, both of which are unknown. We find that
current methods are biased towards light skin tones due to (1) strongly biased
priors that prefer lighter pigmentation and (2) algorithmic solutions that
disregard the light/albedo ambiguity. To address this, we propose a new
evaluation dataset (FAIR) and an algorithm (TRUST) to improve albedo estimation
and, hence, fairness. Specifically, we create the first facial albedo
evaluation benchmark where subjects are balanced in terms of skin color, and
measure accuracy using the Individual Typology Angle (ITA) metric. We then
address the light/albedo ambiguity by building on a key observation: the image
of the full scene -- as opposed to a cropped image of the face -- contains
important information about lighting that can be used for disambiguation. TRUST
regresses facial albedo by conditioning both on the face region and a global
illumination signal obtained from the scene image. Our experimental results
show significant improvement compared to state-of-the-art methods on albedo
estimation, both in terms of accuracy and fairness. The evaluation benchmark
and code will be made available for research purposes at
https://trust.is.tue.mpg.de.Comment: Camera-Ready version, accepted at ECCV202
FLARE: Fast Learning of Animatable and Relightable Mesh Avatars
Our goal is to efficiently learn personalized animatable 3D head avatars from
videos that are geometrically accurate, realistic, relightable, and compatible
with current rendering systems. While 3D meshes enable efficient processing and
are highly portable, they lack realism in terms of shape and appearance. Neural
representations, on the other hand, are realistic but lack compatibility and
are slow to train and render. Our key insight is that it is possible to
efficiently learn high-fidelity 3D mesh representations via differentiable
rendering by exploiting highly-optimized methods from traditional computer
graphics and approximating some of the components with neural networks. To that
end, we introduce FLARE, a technique that enables the creation of animatable
and relightable mesh avatars from a single monocular video. First, we learn a
canonical geometry using a mesh representation, enabling efficient
differentiable rasterization and straightforward animation via learned
blendshapes and linear blend skinning weights. Second, we follow
physically-based rendering and factor observed colors into intrinsic albedo,
roughness, and a neural representation of the illumination, allowing the
learned avatars to be relit in novel scenes. Since our input videos are
captured on a single device with a narrow field of view, modeling the
surrounding environment light is non-trivial. Based on the split-sum
approximation for modeling specular reflections, we address this by
approximating the pre-filtered environment map with a multi-layer perceptron
(MLP) modulated by the surface roughness, eliminating the need to explicitly
model the light. We demonstrate that our mesh-based avatar formulation,
combined with learned deformation, material, and lighting MLPs, produces
avatars with high-quality geometry and appearance, while also being efficient
to train and render compared to existing approaches.Comment: 15 pages, Accepted: ACM Transactions on Graphics (Proceedings of
SIGGRAPH Asia), 202
I M Avatar: Implicit Morphable Head Avatars from Videos
Traditional morphable face models provide fine-grained control over
expression but cannot easily capture geometric and appearance details. Neural
volumetric representations approach photo-realism but are hard to animate and
do not generalize well to unseen expressions. To tackle this problem, we
propose IMavatar (Implicit Morphable avatar), a novel method for learning
implicit head avatars from monocular videos. Inspired by the fine-grained
control mechanisms afforded by conventional 3DMMs, we represent the expression-
and pose-related deformations via learned blendshapes and skinning fields.
These attributes are pose-independent and can be used to morph the canonical
geometry and texture fields given novel expression and pose parameters. We
employ ray tracing and iterative root-finding to locate the canonical surface
intersection for each pixel. A key contribution is our novel analytical
gradient formulation that enables end-to-end training of IMavatars from videos.
We show quantitatively and qualitatively that our method improves geometry and
covers a more complete expression space compared to state-of-the-art methods
Long-term chromospheric activity in southern M dwarfs: Gl 229 A and Gl 752 A
Several late-type stars present activity cycles similar to that of the Sun.
However, these cycles have been mostly studied in F to K stars. Due to their
small intrinsic brightness, M dwarfs are not usually the targets of long-term
observational studies of stellar activity, and their long-term variability is
generally not known. In this work, we study the long-term activity of two M
dwarf stars: Gl 229 A (M1/2) and Gl 752 A (M2.5). We employ medium resolution
echelle spectra obtained at the 2.15 m telescope at the Argentinian observatory
CASLEO between the years 2000 and 2010 and photometric observations obtained
from the ASAS database. We analyzed Ca \II K line-core fluxes and the mean V
magnitude with the Lomb-Scargle periodogram, and we obtain possible activity
cycles of 4 yr and 7 yr for Gl 229 A and Gl 752 A respectively.Comment: Accepted for publication by Astronomical Journal (AJ
The UV surface habitability of Proxima <i>b</i>: first experiments revealing probable life survival to stellar flares
Abstract We use a new interdisciplinary approach to study the UV surface habitability of Proxima b under quiescent and flaring stellar conditions. We assumed planetary atmospheric compositions based on CO2 and N2 and surface pressures from 100 to 5000 mbar. Our results show that the combination of these atmospheric compositions and pressures provide enough shielding from the most damaging UV wavelengths, expanding the ”UV-protective” planetary atmospheric compositions beyond ozone. Additionally, we show that the UV radiation reaching the surface of Proxima b during quiescent conditions would be negligible from the biological point of view, even without an atmosphere. Given that high UV fluxes could challenge the existence of life, then, we experimentally tested the effect that flares would have on microorganisms in a ”worst case scenario” (no UV-shielding). Our results show the impact that a typical flare and a superflare would have on life: when microorganisms receive very high fluences of UVC, such as those expected to reach the surface of Proxima b after a typical flare or a superflare, a fraction of the population is able to survive. Our study suggests that life could cope with highly UV irradiated environments in exoplanets under conditions that cannot be found on Earth
Estimation and inference under economic restrictions
Estimation of economic relationships often requires imposition of constraints such as positivity or monotonicity on each observation. Methods to impose such constraints, however, vary depending upon the estimation technique employed. We describe a general methodology to impose (observation-specific) constraints for the class of linear regression estimators using a method known as constraint weighted bootstrapping. While this method has received attention in the nonparametric regression literature, we show how it can be applied for both parametric and nonparametric estimators. A benefit of this method is that imposing numerous constraints simultaneously can be performed seamlessly. We apply this method to Norwegian dairy farm data to estimate both unconstrained and constrained parametric and nonparametric models
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