Multiplexed acquisition of bidirectional texture functions for materials

Abstract

The bidirectional texture function (BTF) has proven a valuable model for the representation of complex spatiallyvarying material reflectance. Its image-based nature, however, makes material BTFs extremely cumbersome to acquire: in order to adequately sample high-frequency details, many thousands of images of a given material as seen and lit from different directions have to be obtained. Additionally, long exposure times are required to account for the wide dynamic range exhibited by the reflectance of many real-world materials.We propose to significantly reduce the required exposure times by using illumination patterns instead of single light sources ("multiplexed illumination"). A BTF can then be produced by solving an appropriate linear system, exploiting the linearity of the superposition of light. Where necessary, we deal with signal-dependent noise by using a simple linear model derived from an existing database of material BTFs as a prior. We demonstrate the feasibility of our method for a number of real-world materials in a camera dome scenario. Figure 1. Our acquisition setup displaying an S-matrix pattern.

A Catalog Sample of Low-mass Galaxies Observed in X-Rays with Central Candidate Black Holes

“…When the distance is greater than 3 ′′ , the source could not be a non-nuclear black hole candidate (possibly a ULX, see in this respect Swartz et al 2008 for a discussion on the number of ULXs found in low mass galaxies). Note also that for sources #35 (NGC 4117) and #50 (NGC 4395), our estimate of the candidate black hole mass is a factor ≃ 10 larger (but still consistent due to the large intrinsic scatter of the fundamental plane relation) than the values derived by Woo & Urry (2002) and den Brok et al (2015), respectively, when studying the gas dynamics in the galaxies and/or using the virial assumption for the broad emission lines while determining the broadline region size from either reverberation mapping or optical luminosity.…”