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Connecting measured BRDFs to analytic BRDFs by data-driven diffuse-specular separation
摘要： The bidirectional reflectance distribution function (BRDF) is crucial for modeling the appearance of real-world materials. In production rendering, analytic BRDF models are often used to approximate the surface appearance since they are compact and flexible. Measured BRDFs usually have a more realistic appearance, but consume much more storage and are hard to modify. In this paper, we propose a novel framework for connecting measured and analytic BRDFs. First, we develop a robust method for separating a measured BRDF into diffuse and specular components. This is commonly done in analytic models, but has been difficult previously to do explicitly for measured BRDFs. This diffuse-specular separation allows novel measured BRDF editing on the diffuse and specular parts separately. In addition, we conduct analysis on each part of the measured BRDF, and demonstrate a more intuitive and lower-dimensional PCA model than Nielsen et al. [2015]. In fact, our measured BRDF model has the same number of parameters (8 parameters) as the commonly used analytic models, such as the GGX model. Finally, we visualize the analytic and measured BRDFs in the same space, and directly demonstrate their similarities and differences. We also design an analytic fitting algorithm for two-lobe materials, which is more robust, efficient and simple, compared to previous non-convex optimization-based analytic fitting methods.
关键词： Analytic BRDF models,Measured BRDF editing,Measured BRDF models,Analytic BRDF fitting
更新于2025-09-23 15:23:52
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Investigation of Sentinel-2 Bidirectional Reflectance Hot-Spot Sensing Conditions
摘要： Directional reflectance effects, often described by the bidirectional reflectance distribution function (BRDF), occur in Sentinel-2 multispectral instrument reflectance. The bidirectional hot-spot is a special case of the BRDF used to describe the increased backscatter reflectance that occurs over most surfaces when the solar and viewing directions coincide. A global year of Sentinel-2A metadata extracted using the Committee on Earth Observation Satellite Visualization Environment (COVE) tool and an established astronomical model were used to quantify the range of solar geometry and scattering angles expected in Sentinel-2A data. The established astronomical model was adapted to be Sentinel-2A specific and was parameterized as a function of the sensor acquisition date and nadir latitude. Solar zenith angles varied from 15.335° to 91.454°, and the scattering angles varied from 84.714° to 173.967°. To confirm the global COVE results, the scattering angles of a sample of Sentinel-2A data were examined and differed by less than 0.17° with respect to the COVE data. Given that hot-spots are only apparent when the scattering angle is close to 180°, we conclude that hot-spot will not occur in Sentinel-2A data. Equations and software to predict the scattering angle at the Sentinel-2A swath edge as a function of acquisition date and nadir latitude are provided so users may obtain data over a range of scattering angles in support of their BRDF studies.
关键词： bidirectional reflectance distribution function (BRDF),Bidirectional hot-spot,scattering angle,solar geometry,Sentinel-2
更新于2025-09-23 15:23:52
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Stability Monitoring of the VIIRS Day/Night Band over Dome C with a Lunar Irradiance Model and BRDF Correction
摘要： The unique feature of the Visible Infrared Imager Radiometer Suite (VIIRS) day/night band (DNB) is its ability to take quantitative measurements of low-light scenes at night. In order to monitor the stability of the high gain stage (HGS) of the DNB, nighttime observations over the Dome C site under moonlight are analyzed in this study. The Miller and Turner 2009 (MT2009) lunar irradiance model has been used to simulate lunar illumination over Dome C. However, the MT2009 model does not differentiate the waxing and waning lunar phases. In this paper, the MT-SWC (SeaWiFS Corrected) lunar irradiance model differentiating the waxing and waning lunar phases is derived by correcting the MT2009 model using lunar observations made by the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS). In addition, a top of atmosphere (TOA) bi-directional reflectance distribution function (BRDF) model during nighttime over Dome C is developed to remove the angular dependence from the nighttime TOA reflectance. The long-term stability monitoring of the DNB high-gain stage (HGS) reveals a lower reflectance factor in 2012 in comparison to the following years, which can be traced back to the change in relative spectral response (RSR) of National Oceanic & Atmospheric Administration's (NOAA's) Interface Data Processing Segment (IDPS) VIIRS DNB in April 2013. It also shows the radiometric stability of DNB data, with long-term stability of less than 1.58% over the periods from 2013 to 2016. This method can be used to monitor the radiometric stability of other low-light observing sensors using vicarious calibration sites under moonlight illumination.
关键词： visible infrared imaging radiometer suite (VIIRS),Miller and Turner 2009 (MT2009),Sea-Viewing Wide Field-of-View Sensor (SeaWiFS),Dome C site,day/night band (DNB),lunar observations,BRDF effect
更新于2025-09-23 15:22:29
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Potential Investigation of Linking PROSAIL with the Ross-Li BRDF Model for Vegetation Characterization
摘要： Methods that link different models for investigating the retrieval of canopy biophysical/structural variables have been substantially adopted in the remote sensing community. To retrieve global biophysical parameters from multiangle data, the kernel-driven bidirectional reflectance distribution function (BRDF) model has been widely applied to satellite multiangle observations to model (interpolate/extrapolate) the bidirectional reflectance factor (BRF) in an arbitrary direction of viewing and solar geometries. Such modeled BRFs, as an essential information source, are then input into an inversion procedure that is devised through a large number of simulation analyses from some widely used physical models that can generalize such an inversion relationship between the BRFs (or their simple algebraic composite) and the biophysical/structural parameter. Therefore, evaluation of such a link between physical models and kernel-driven models contributes to the development of such inversion procedures to accurately retrieve vegetation properties, particularly based on the operational global BRDF parameters derived from satellite multiangle observations (e.g., MODIS). In this study, the main objective is to investigate the potential for linking a popular physical model (PROSAIL) with the widely used kernel-driven Ross-Li models. To do this, the BRFs and albedo are generated by the physical PROSAIL in a forward model, and then the simulated BRFs are input into the kernel-driven BRDF model for retrieval of the BRFs and albedo in the same viewing and solar geometries. To further strengthen such an investigation, a variety of field-measured multiangle reflectances have also been used to investigate the potential for linking these two models. For simulated BRFs generated by the PROSAIL model at 659 and 865 nm, the two models are generally comparable to each other, and the resultant root mean square errors (RMSEs) are 0.0092 and 0.0355, respectively, although some discrepancy in the simulated BRFs can be found at large average leaf angle (ALA) values. Unsurprisingly, albedos generated by the method are quite consistent, and 99.98% and 97.99% of the simulated white sky albedo (WSA) has a divergence less than 0.02. For the field measurements, the kernel-driven model presents somewhat better model-observation congruence than the PROSAIL model. The results show that these models have an overall good consistency for both field-measured and model-simulated BRFs. Therefore, there is potential for linking these two models for looking into the retrieval of canopy biophysical/structural variables through a simulation method, particularly from the current archive of the global routine MODIS BRDF parameters that were produced by the kernel-driven BRDF model; however, erectophile vegetation must be further examined.
关键词： PROSAIL model,the kernel-driven Ross-Li model,BRDF,model linking,Anisotropy Flat Index (AFX),albedo
更新于2025-09-23 15:22:29
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Infrared characteristics of satellite based on bidirectional reflection distribution function
摘要： With the development of space industry, the requirements of space monitoring technology are becoming higher and higher. The infrared characteristics of on-orbit satellite were studied based on the satellite's flying attitude, background, material and orbit, etc. Bidirectional reflection distribution function (BRDF) was introduced to describe the characteristics of infrared reflection of the element, and a mathematical model of reflected radiation was established by summing the reflection of elements. The accuracy of the Torrance-Sparrow model was verified based on the measured data of the BRDF of the satellite's material. The relationship between the spectral radiance of satellite and the angle of observation was discussed. By comparing the differences in the variation of reflected solar radiance with flight period and the distribution of the radiant intensity between the diffuse reflection model and the BRDF model, the result is analyzed that the BRDF model which based on the reflection of the material can better reflect the characteristics of infrared radiation of satellite.
关键词： BRDF,Spectral radiance,Diffuse reflection,Satellite
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Validation of Global Land Surface Satellite Phase-2 Surface Broadband Albedo Product
摘要： Surface broadband albedo is a critical parameter in surface radiation budget (SRB), which controls the input, separation, and allocation of the Earth’s surface energy. Recently, a Global LAnd Surface Satellite (GLASS) phase-2 surface broadband albedo product has been generated from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Very High Resolution Radiometer (AVHRR) data. In this study, we present a preliminary validation of the GLASS phase-2 surface broadband albedo with the FLUXNET 2015 dataset. The results show that the GLASS phase-2 surface broadband albedo product has a reasonable good accuracy compared with the currently widely used surface albedo dataset, and can provides more reliable estimations of surface albedo at the seasonal snowfall and snowmelt regions. In addition, the GLASS phase-2 surface albedo product is a long-term, global covered (including land and ocean surfaces) dataset, which can be applied in various scenarios of SRB and climate change studies.
关键词： validation,BRDF,FLUXNET,surface radiation budget,Albedo
更新于2025-09-23 15:21:21
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Multi Pole Microwave Filtering using Brillouin Scattering in Silicon
摘要： Acquiring general material appearance with hand-held consumer RGB-D cameras is dif?cult for casual users, due to the inaccuracy in reconstructed camera poses and geometry, as well as the unknown lighting that is coupled with materials in measured color images. To tackle these challenges, we present a novel technique for estimating the spatially varying isotropic surface re?ectance, solely from color and depth images captured with an RGB-D camera under unknown environment illumination. The core of our approach is a joint optimization, which alternates among solving for plausible camera poses, materials, the environment lighting and normals. To re?ne camera poses, we exploit the rich spatial and view-dependent variations of materials, treating the object as a localization-self-calibrating model. To recover the unknown lighting, measured color images along with the current estimate of materials are used in a global optimization, ef?ciently solved by exploiting the sparsity in the wavelet domain. We demonstrate the substantially improved quality of estimated appearance on a variety of daily objects.
关键词： RGB-D camera,joint optimization,spatially varying BRDF
更新于2025-09-23 15:19:57
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[ACM Press the 16th ACM SIGGRAPH International Conference - Tokyo, Japan (2018.12.02-2018.12.03)] Proceedings of the 16th ACM SIGGRAPH International Conference on Virtual-Reality Continuum and its Applications in Industry - VRCAI '18 - Projection mapping based on BRDF reconstruction from single RGBD image
摘要： There have been many researches on projection mapping focused on target objects tracking, geometric shape recovering or virtual materials simulating such as clothes. However, few people pay attention to the material of target object which actually influences the visual results of projection. We present a new projection mapping framework based on BRDF reconstruction for the goal of more real projection results by enhancing the effects of Augmented Reality. In the framework, 3D computer vision method is used to reconstruct the BRDF of target object with a single RGBD image. A new algorithm is proposed using two Convolutional Neural Networks(CNN) which can predict both normal map and reflectance map of the target surface simultaneously with the RGBD image. The predicted maps are used to render the content to be projected onto the target object. Our BRDF reconstruction algorithm can recover several materials in one scene correctly in use of just one image. Experimental results show our framework has impressive performance and relatively accurate consequence.
关键词： BRDF Reconstruction,Projection Mapping,Augmented Reality
更新于2025-09-19 17:15:36
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[IEEE 2019 International Conference on 3D Vision (3DV) - Québec City, QC, Canada (2019.9.16-2019.9.19)] 2019 International Conference on 3D Vision (3DV) - Real-Time Multi-Material Reflectance Reconstruction for Large-Scale Scenes Under Uncontrolled Illumination from RGB-D Image Sequences
摘要： Real-time re?ectance reconstruction under uncontrolled illumination conditions is well-known to be a challenging task due to the complex interplay of scene geometry, surface re?ectance and illumination. Nonetheless, recent works succeed in recovering both unknown re?ectance and illumination in an uncontrolled setting. However, they are either limited regarding the scene complexity (single objects / homogeneous materials) or are not suitable for real-time applications. Our proposed method enables the recovery of heterogeneous surface re?ectance (multiple objects and spatially varying materials) in complex scenes at real-time frame rates. We achieve this goal in the following way: First, we perform a 3D scene reconstruction from an input RGB-D stream in real-time. We then use a deep learning based method to estimate Ward BRDF parameters from observations gathered from individual segmented scene objects. Subsequently we re?ne these re?ectance parameters to allow for spatial variations across the object surfaces. We evaluate our method on synthetic scenes and successfully apply it to real-world data.
关键词： deep learning,RGB-D image sequences,Ward BRDF parameters,uncontrolled illumination,Real-time re?ectance reconstruction
更新于2025-09-12 10:27:22
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Radiative Heat Transfer in Two-Dimensional Cylindrical Medium Coupled with BRDF Surface
摘要： For radiative heat transfer analysis and temperature measurements, the surface is usually assumed to be blackbody, diffuse, or specular, which may cause obvious errors under actual working conditions. The bidirectional reflectance distribution function (BRDF), which is considered as a relatively strict approach for characterizing a real surface, has been adopted in heat transfer analysis. In this study, two BRDF models—the Minnaert model and the Torrance and Sparrow model—are applied to investigate the effects of different boundary conditions on the radiative heat transfer. Additionally, the distribution of ratios of energy scattered by the medium or reflected by the boundary surface method is extended to solve the radiative transfer in a two-dimensional graded-index medium coupled with BRDF surfaces in a cylindrical coordinate system. The results show that greater deviation of the BRDF surface from the diffuse characteristics yields a larger difference of the radiative heat flux and intensity distributions between the BRDF and the diffuse surface. The radiative heat flux deviation reaches 12.78%, and more significant differences exist in the radiative intensity along some directions under different boundary conditions. The specular reflection plays a leading role at high reflection angles. However, the increased scattering ability can weaken the influence of the reflection of the BRDF on the radiative intensity distributions.
关键词： radiative heat transfer,graded-index medium,Torrance and Sparrow model,Minnaert model,BRDF surface,cylindrical medium
更新于2025-09-11 14:15:04