1,231 research outputs found
Single-shot layered reflectance separation using a polarized light field camera
We present a novel computational photography technique for single shot separation of diffuse/specular reflectance as well as novel angular domain separation of layered reflectance. Our solution consists of a two-way polarized light field (TPLF) camera which simultaneously captures two orthogonal states of polarization. A single photograph of a subject acquired with the TPLF camera under polarized illumination then enables standard separation of diffuse (depolarizing) and polarization preserving specular reflectance using light field sampling. We further demonstrate that the acquired data also enables novel angular separation of layered reflectance including separation of specular reflectance and single scattering in the polarization preserving component, and separation of shallow scattering from deep scattering in the depolarizing component. We apply our approach for efficient acquisition of facial reflectance including diffuse and specular normal maps, and novel separation of photometric normals into layered reflectance normals for layered facial renderings. We demonstrate our proposed single shot layered reflectance separation to be comparable to an existing multi-shot technique that relies on structured lighting while achieving separation results under a variety of illumination conditions
Depth Super-Resolution Meets Uncalibrated Photometric Stereo
A novel depth super-resolution approach for RGB-D sensors is presented. It
disambiguates depth super-resolution through high-resolution photometric clues
and, symmetrically, it disambiguates uncalibrated photometric stereo through
low-resolution depth cues. To this end, an RGB-D sequence is acquired from the
same viewing angle, while illuminating the scene from various uncalibrated
directions. This sequence is handled by a variational framework which fits
high-resolution shape and reflectance, as well as lighting, to both the
low-resolution depth measurements and the high-resolution RGB ones. The key
novelty consists in a new PDE-based photometric stereo regularizer which
implicitly ensures surface regularity. This allows to carry out depth
super-resolution in a purely data-driven manner, without the need for any
ad-hoc prior or material calibration. Real-world experiments are carried out
using an out-of-the-box RGB-D sensor and a hand-held LED light source.Comment: International Conference on Computer Vision (ICCV) Workshop, 201
Human-centric light sensing and estimation from RGBD images: the invisible light switch
Lighting design in indoor environments is of primary importance for at least two reasons: 1) people should perceive an adequate light; 2) an effective lighting design means consistent energy saving. We present the Invisible Light Switch (ILS) to address both aspects. ILS dynamically adjusts the room illumination level to save energy while maintaining constant the light level perception of the users. So the energy saving is invisible to them. Our proposed ILS leverages a radiosity model to estimate the light level which is perceived by a person within an indoor environment, taking into account the person position and her/his viewing frustum (head pose). ILS may therefore dim those luminaires, which are not seen by the user, resulting in an effective energy saving, especially in large open offices (where light may otherwise be ON everywhere for a single person). To quantify the system performance, we have collected a new dataset where people wear luxmeter devices while working in office rooms. The luxmeters measure the amount of light (in Lux) reaching the people gaze, which we consider a proxy to their illumination level perception. Our initial results are promising: in a room with 8 LED luminaires, the energy consumption in a day may be reduced from 18585 to 6206 watts with ILS (currently needing 1560 watts for operations). While doing so, the drop in perceived lighting decreases by just 200 lux, a value considered negligible when the original illumination level is above 1200 lux, as is normally the case in offices
Human-centric light sensing and estimation from RGBD images: The invisible light switch
Lighting design in indoor environments is of primary importance for at least
two reasons: 1) people should perceive an adequate light; 2) an effective
lighting design means consistent energy saving. We present the Invisible Light
Switch (ILS) to address both aspects. ILS dynamically adjusts the room
illumination level to save energy while maintaining constant the light level
perception of the users. So the energy saving is invisible to them. Our
proposed ILS leverages a radiosity model to estimate the light level which is
perceived by a person within an indoor environment, taking into account the
person position and her/his viewing frustum (head pose). ILS may therefore dim
those luminaires, which are not seen by the user, resulting in an effective
energy saving, especially in large open offices (where light may otherwise be
ON everywhere for a single person). To quantify the system performance, we have
collected a new dataset where people wear luxmeter devices while working in
office rooms. The luxmeters measure the amount of light (in Lux) reaching the
people gaze, which we consider a proxy to their illumination level perception.
Our initial results are promising: in a room with 8 LED luminaires, the energy
consumption in a day may be reduced from 18585 to 6206 watts with ILS
(currently needing 1560 watts for operations). While doing so, the drop in
perceived lighting decreases by just 200 lux, a value considered negligible
when the original illumination level is above 1200 lux, as is normally the case
in offices
A Novel Framework for Highlight Reflectance Transformation Imaging
We propose a novel pipeline and related software tools for processing the multi-light image collections (MLICs) acquired in different application contexts to obtain shape and appearance information of captured surfaces, as well as to derive compact relightable representations of them. Our pipeline extends the popular Highlight Reflectance Transformation Imaging (H-RTI) framework, which is widely used in the Cultural Heritage domain. We support, in particular, perspective camera modeling, per-pixel interpolated light direction estimation, as well as light normalization correcting vignetting and uneven non-directional illumination. Furthermore, we propose two novel easy-to-use software tools to simplify all processing steps. The tools, in addition to support easy processing and encoding of pixel data, implement a variety of visualizations, as well as multiple reflectance-model-fitting options. Experimental tests on synthetic and real-world MLICs demonstrate the usefulness of the novel algorithmic framework and the potential benefits of the proposed tools for end-user applications.Terms: "European Union (EU)" & "Horizon 2020" / Action: H2020-EU.3.6.3. - Reflective societies - cultural heritage and European identity / Acronym: Scan4Reco / Grant number: 665091DSURF project (PRIN 2015) funded by the Italian Ministry of University and ResearchSardinian Regional Authorities under projects VIGEC and Vis&VideoLa
Multiple scattering of polarized radiation by non-spherical grains: first results
We present the first numerical radiative transfer simulation of multiple
light scattering in dust configurations containing aligned non-spherical
(spheroidal) dust grains. Such models are especially important if one wants to
explain the circular polarization of light, observed in a variety of
astronomical objects. The radiative transfer problem is solved on the basis of
the Monte Carlo method. Test simulations, confirming the correct numerical
implementation of the scattering mechanism, are presented. As a first
application, we investigate the linear and circular polarization of light
coming from a spherical circumstellar shell. This shell contains perfectly
aligned prolate or oblate spheroidal grains. The most remarkable features of
the simulated linear polarization maps are so-called polarization null points
where the reversal of polarization occurs. They appear in the case when the
grain alignment axis is perpendicular to the line of sight. The maps of
circular polarization have a sector-like structure with maxima at the ends of
lines inclined to the grain alignment axis by \pm 45\degr.Comment: 13 pages, 14 figures, accepted by A&
- …