1,721,501 research outputs found
Differentiable Rendering of Neural SDFs through Reparameterization
Full text linkWe present a method to automatically compute correct gradients with respect
to geometric scene parameters in neural SDF renderers. Recent physically-based
differentiable rendering techniques for meshes have used edge-sampling to
handle discontinuities, particularly at object silhouettes, but SDFs do not
have a simple parametric form amenable to sampling. Instead, our approach
builds on area-sampling techniques and develops a continuous warping function
for SDFs to account for these discontinuities. Our method leverages the
distance to surface encoded in an SDF and uses quadrature on sphere tracer
points to compute this warping function. We further show that this can be done
by subsampling the points to make the method tractable for neural SDFs. Our
differentiable renderer can be used to optimize neural shapes from multi-view
images and produces comparable 3D reconstructions to recent SDF-based inverse
rendering methods, without the need for 2D segmentation masks to guide the
geometry optimization and no volumetric approximations to the geometry
Real-time collision detection between general SDFs
No full textSigned Distance Fields (SDFs) have found widespread utility in collision detection applications due to their superior query efficiency and ability to represent continuous geometries. However, little attention has been paid to calculating the intersection of two arbitrary SDFs. In this paper, we propose a novel, accurate, and real-time approach for SDF-based collision detection between two solids, both represented as SDFs. Our primary strategy entails using interval calculations and the SDF gradient to guide the search for intersection points within the geometry. For arbitrary objects, we take inspiration from existing collision detection pipelines and segment the two SDFs into multiple parts with bounding volumes. Once potential collisions between two parts are identified, our method quickly computes comprehensive intersection information such as penetration depth, contact points, and contact normals. Our method is general in that it accepts both continuous and discrete SDF representations. Experiment results show that our method can detect collisions in high-precision models in real time, highlighting its potential for a wide range of applications in computer graphics and virtual reality
Lipschitz Pruning: Hierarchical Simplification of Primitive‐Based SDFs
No full textEurographics 2025 Best Paper Honorable MentionInternational audienceRendering tree‐based analytical Signed Distance Fields (SDFs) through sphere tracing often requires to evaluate many primitives per tracing step, for many steps per pixel of the end image. This cost quickly becomes prohibitive as the number of primitives that constitute the SDF grows. In this paper, we alleviate this cost by computing local pruned trees that are equivalent to the full tree within their region of space while being much faster to evaluate. We introduce an efficient hierarchical tree pruning method based on the Lipschitz property of SDFs, which is compatible with hard and smooth CSG operators. We propose a GPU implementation that enables real‐time sphere tracing of complex SDFs composed of thousands of primitives with dynamic animation. Our pruning technique provides significant speedups for SDF evaluation in general, which we demonstrate on sphere tracing tasks but could also lead to significant improvement for SDF discretization or polygonization
Lipschitz Pruning: Hierarchical Simplification of Primitive-Based SDFs
No full textRendering tree-based analytical Signed Distance Fields (SDFs) through sphere tracing often requires to evaluate many primitives per tracing step, for many steps per pixel of the end image. This cost quickly becomes prohibitive as the number of primitives that constitute the SDF grows. In this paper, we alleviate this cost by computing local pruned trees that are equivalent to the full tree within their region of space while being much faster to evaluate. We introduce an efficient hierarchical tree pruning method based on the Lipschitz property of SDFs, which is compatible with hard and smooth CSG operators. We propose a GPU implementation that enables real-time sphere tracing of complex SDFs composed of thousands of primitives with dynamic animation. Our pruning technique provides significant speedups for SDF evaluation in general, which we demonstrate on sphere tracing tasks but could also lead to significant improvement for SDF discretization or polygonization.Computer Graphics ForumThe Shape of Rendering44
Commentary on : Pseudo-True SDFs in Conditional Asset Pricing Models
No full textAsset pricing models are, at best, approximations of reality and are bound to be misspecified. However, it can still be useful to empirically evaluate the degree of model misspecification and the relative performance of competing asset pricing models using actual data. In their seminal paper, Hansen and Jagannathan (1997, HJ hereafter) propose two measures of model misspecification, which are now routinely used for parameter estimation, specification testing, and model selection. The first one measures the distance between the proposed stochastic discount factor (SDF) and the set of admissible SDFs (i.e., the set of SDFs that price a given set of test assets correctly). The second one measures the distance between the..
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comment on: Pseudo-True SDFs in Conditional Asset Pricing Models. Comparing Fixed-versus Vanishing-Bandwidth Estimators of Pseudo-True SDFs
Full text linkThe paper by Antoine, Proulx, and Renault (2018) (APR) deals with the econometric definition, economic interpretation, and statistical estimation of the pseudo-true stochastic discount factor (SDF) in misspecified conditional asset pricing models. The paper revolves around fundamental issues like the role of conditioning information and omitted risk factors, and has non-trivial interactions with the current debate in the literature on the impact of weak factors (weak identification) for assessing asset pricing models. Building on, and substantially extending, previous contributions in the literature, the approach of the authors to define a pseudo-true SDF relies on the minimizers of econometric criteria based on a conditional version of the Hansen–Jagannathan (HJ) distance, that is, an average across states of squared conditional pricing errors. The authors provide an insightful discussion of the economic interpretation of pseudo-true SDFs. APR advocate the use of a fixed bandwidth (i.e., independent of the sample size) when estimating the conditional pricing errors by kernel regression methods to facilitate statistical analysis. This route leads to bandwidth-dependent pseudo-true SDF parameters and estimators thereof.
In our discussion, we investigate the different definitions of pseudo-true SDFs and interpret the fixed-bandwidth proposal as a model calibration which down-weights highfrequency Fourier components of the conditional pricing errors (Section 1). We compare the statistical properties of pseudo-true SDF parameters’ estimators relying on vanishing versus fixed bandwidth, and provide a condition under which the former have a smaller asymptotic variance than the latter (or viceversa). We look at these topics through the lens of misspecified conditional linear SDF models in which priced risk factors are omitted using both simulated and real data (Section 3). We skip regularity conditions and relegate some technical derivations in the Appendix of the paper
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Incorporating Water Sensitive Urban Design (WSUD) with Municipal Spatial Development Frameworks (SDFs)
No full textMSc (Environmental Management), North-West University, Potchefstroom CampusExtreme climate events are frequent in many parts of the world. Considering these climate events are accompanied by a growing population, resulting in an increased water demand from local municipalities, alternative water-related development strategies should be considered. Incorporating Water Sensitive Urban Design (WSUD) within municipal Spatial Development Frameworks (SDFs) can enhance the sustainability of urban areas. Water resource management is one of the most significant challenges experienced in the 21st century. South Africa is a semi-arid country with variations in rainfall, temporal and spatial precipitation, resulting in a more complex situation. It is expected that by 2030, there will be a water demand and supply gap of up to 17% due to increased urbanisation, population and economic growth, climate change and unrealistic living standards. The relationship between water and land use is not understood, and spatial planning and land-use documents barely address water-related land-use implications. This study aimed to understand the level of incorporation of WSUD within Municipal SDFs. The study reflects on the urban water challenges experienced on local and international levels. Opportunities are identified as to how municipalities can, and should, give effect to WSUD. This was achieved by evaluating four municipal SDFs using the WSUD principles. To prove that municipal SDFs do not incorporate WSUD to secure water sustainability, Witzenberg Local Municipality, Dawid Kruiper Local Municipality, Mangaung Metropolitan Municipality and Cape Town Metropolitan Municipality were selected as case studies. A review of each case study’s SDF revealed that the concept of WSUD is not incorporated fully. An extensive evaluation revealed that sustainable water management and planning can be achieved by incorporating WSUD. The study provides a framework for WSUD with guidelines on water sensitivity and conservation for local authorities. This will ensure that municipalities can secure adequate water resources in the future.Master
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