The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Wolff - One of the best experts on this subject based on the ideXlab platform.
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CVPR - Surface curvature from integrability
Proceedings of IEEE Conference on Computer Vision and Pattern Recognition CVPR-94, 1994Co-Authors: Fan, WolffAbstract:We present a multiple Illumination technique that directly recovers the viewer-centered curvature matrix up to a scalar factor, at each mutually illuminated point on a smooth object surface. This technique is completely independent of knowledge of Incident Illumination orientation, local surface orientation, or diffuse surface albedo. The cornerstone of this technique is the use of the integrability constraint which is a fundamental mathematical property of smooth surfaces. The integrability constraint allows the derivation of an equation at each object point, which is linear in terms of quantities involving the initially unknown parameters of Incident Illumination orientation. These quantities, which we call the gradient ratio constants, can be simultaneously solved for from five or more equations arising from the same number of object points. We show that deriving these gradient ratio constants provides just enough calibration information about Incident Illumination geometry to compute the viewer-centered curvature matrix at each object point, up to a scalar multiple. We demonstrate two important applications of this technique: segmentation of the object surface by sign of Gaussian curvature, and further segmentation of non-negative Gaussian curvature into convexity and concavity. >
Norman J. Mccormick - One of the best experts on this subject based on the ideXlab platform.
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Asymptotic optical depths in source-free ocean waters.
Applied optics, 2003Co-Authors: Brian D. Piening, Norman J. MccormickAbstract:The depth dependence for which the downward diffuse attenuation coefficient, the upward-to-downward plane irradiance ratio, the vertically upward radiance-to-downward plane irradiance ratio, and the mean cosine of the radiance depend negligibly on the surface Incident Illumination have been examined. The depths at which these coefficients approach to within a specified percent of their asymptotic values depends significantly on the characteristics of the Incident Illumination and on the inherent optical properties of the water. This information is useful when solving inverse ocean optics problems with a method for which the radiance is assumed to be approximately in the asymptotic regime.
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Exact P{sub N} Method Solutions
Nuclear Science and Engineering, 2001Co-Authors: Norman J. MccormickAbstract:The spherical harmonics (P{sub N}) solution at the surface of a source-free half-space is investigated to determine conditions for which exact results can be obtained with an approximation of any odd order N. For isotropic scattering, an exact solution for the net current can be obtained if the Incident Illumination comes from an isotropic plane source, which extends the observation of Garcia and Siewert that an exact solution for the scalar flux can be obtained if the Incident Illumination is constant with the cosine of the polar angle. An exact solution for the scalar flux at the interface between two isotropic-scattering, half-space media also can be obtained with a finite N for a spatially uniform source in one half-space.
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Exact PN Method Solutions
Nuclear Science and Engineering, 2001Co-Authors: Norman J. MccormickAbstract:The spherical harmonics (P N ) solution at the surface of a source-free half-space is investigated to determine conditions for which exact results can be obtained with an approximation of any odd order N. For isotropic scattering, an exact solution for the net current can be obtained if the Incident Illumination comes from an isotropic plane source, which extends the observation of Garcia and Siewert that an exact solution for the scalar flux can be obtained if the Incident Illumination is constant with the cosine of the polar angle. An exact solution for the scalar flux at the interface between two isotropic-scattering, half-space media also can be obtained with a finite N for a spatially uniform source in one half-space.
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Design of an integrating cavity absorption meter
Applied optics, 1999Co-Authors: Dane M. Hobbs, Norman J. MccormickAbstract:The design of integrating cavity absorption meters of general geometry is analyzed for cases in which the Incident Illumination of the cavity is spatially uniform and isotropic, such as the meter of Fry et al. [Appl. Opt. 31, 2055 (1992)]. The analysis by Kirk [Appl. Opt. 34, 4397 (1995)] for the probability of photon survival in a spherical meter is extended to general geometries. An estimate of the effect of the shape of the cavity on the estimated absorption coefficient is given.
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Unified approach to analytical solutions of three inverse transport problems
Progress in Nuclear Energy, 1999Co-Authors: Norman J. MccormickAbstract:With two general sets of surface quadratic equations, analytical solutions are developed for three inverse problems for a homogeneous half space that is uniformly illuminated over its surface. The problems considered are the determination of the mean number of secondaries plus the scattering properties of the medium, the determination of the Incident Illumination, and the determination of a spatially-dependent interior source within the medium. The results for the latter two problems are only marginally successful.
Noah Snavely - One of the best experts on this subject based on the ideXlab platform.
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Lighthouse: Predicting Lighting Volumes for Spatially-Coherent Illumination.
arXiv: Computer Vision and Pattern Recognition, 2020Co-Authors: Pratul P. Srinivasan, Ben Mildenhall, Matthew Tancik, Jonathan T. Barron, Richard Tucker, Noah SnavelyAbstract:We present a deep learning solution for estimating the Incident Illumination at any 3D location within a scene from an input narrow-baseline stereo image pair. Previous approaches for predicting global Illumination from images either predict just a single Illumination for the entire scene, or separately estimate the Illumination at each 3D location without enforcing that the predictions are consistent with the same 3D scene. Instead, we propose a deep learning model that estimates a 3D volumetric RGBA model of a scene, including content outside the observed field of view, and then uses standard volume rendering to estimate the Incident Illumination at any 3D location within that volume. Our model is trained without any ground truth 3D data and only requires a held-out perspective view near the input stereo pair and a spherical panorama taken within each scene as supervision, as opposed to prior methods for spatially-varying lighting estimation, which require ground truth scene geometry for training. We demonstrate that our method can predict consistent spatially-varying lighting that is convincing enough to plausibly relight and insert highly specular virtual objects into real images.
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CVPR - Lighthouse: Predicting Lighting Volumes for Spatially-Coherent Illumination
2020 IEEE CVF Conference on Computer Vision and Pattern Recognition (CVPR), 2020Co-Authors: Pratul P. Srinivasan, Ben Mildenhall, Matthew Tancik, Jonathan T. Barron, Richard Tucker, Noah SnavelyAbstract:We present a deep learning solution for estimating the Incident Illumination at any 3D location within a scene from an input narrow-baseline stereo image pair. Previous approaches for predicting global Illumination from images either predict just a single Illumination for the entire scene, or separately estimate the Illumination at each 3D location without enforcing that the predictions are consistent with the same 3D scene. Instead, we propose a deep learning model that estimates a 3D volumetric RGBA model of a scene, including content outside the observed field of view, and then uses standard volume rendering to estimate the Incident Illumination at any 3D location within that volume. Our model is trained without any ground truth 3D data and only requires a held-out perspective view near the input stereo pair and a spherical panorama taken within each scene as supervision, as opposed to prior methods for spatially-varying lighting estimation, which require ground truth scene geometry for training. We demonstrate that our method can predict consistent spatially-varying lighting that is convincing enough to plausibly relight and insert highly specular virtual objects into real images.
John M. Guerra - One of the best experts on this subject based on the ideXlab platform.
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Super‐resolution through Illumination by diffraction‐born evanescent waves
Applied Physics Letters, 1995Co-Authors: John M. GuerraAbstract:A diffraction grating in silicon with 50 nm lines and spaces is illuminated with diffraction‐born evanescent waves from its transparent replica. A rotation φ between the gratings results in a set of fringes with period λf that is larger than the period of the original gratings by a magnification factor M. These fringes are induced and observed with a photon tunneling microscope having an Incident Illumination of 650 nm in air. This super‐resolution by what may be considered a form of optical heterodyning with evanescent waves is discussed.
Wolfgang Heidrich - One of the best experts on this subject based on the ideXlab platform.
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CVPR - Material Classification Using Raw Time-of-Flight Measurements
2016 IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2016Co-Authors: Felix Heide, Robin Swanson, Jonathan Klein, Clara Callenberg, Matthias B. Hullin, Wolfgang HeidrichAbstract:We propose a material classification method using raw time-of-flight (ToF) measurements. ToF cameras capture the correlation between a reference signal and the temporal response of material to Incident Illumination. Such measurements encode unique signatures of the material, i.e. the degree of subsurface scattering inside a volume. Subsequently, it offers an orthogonal domain of feature representation compared to conventional spatial and angular reflectance-based approaches. We demonstrate the effectiveness, robustness, and efficiency of our method through experiments and comparisons of real-world materials.
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Correlated visibility sampling for direct Illumination
The Visual Computer, 2006Co-Authors: Abhijeet Ghosh, Wolfgang HeidrichAbstract:State-of-the-art importance sampling strategies for direct Illumination take into account the importance of the Incident Illumination, as well as the surface BRDF. Hence, these techniques achieve low variance in unoccluded regions. However, the resulting images still have noise in partially occluded regions as these techniques do not take visibility into account during the sampling process.We introduce the notion of correlated visibility sampling, which considers visibility in partially occluded regions during the sampling process, thereby improving the quality of the shadowed regions. We aim to draw samples in the partially occluded regions according to the triple product of the Incident Illumination, BRDF and visibility using Monte Carlo sampling followed by Metropolis sampling.
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SIGGRAPH Sketches - Correlated visibility sampling for direct Illumination
ACM SIGGRAPH 2005 Sketches on - SIGGRAPH '05, 2005Co-Authors: Abhijeet Ghosh, Wolfgang HeidrichAbstract:State-of-the-art importance sampling strategies for direct Illumination take into account the importance of the Incident Illumination, as well as the surface BRDF. Hence, these techniques achieve low variance in unoccluded regions. However, the resulting images still have noise in partially occluded regions as these techniques do not take visibility into account during the sampling process.
