Automated three-axis gonioreflectometer for computer graphics applications

We describe an automated three-axis BRDF measurement instrument that can help increase the physical realism of computer graphics images by providing light scattering data for the surfaces within a synthetic scene that is to be rendered. To our knowledge, the instrument is unique in combining wide angular coverage (beyond 85 ° from the surface normal), dense sampling of the visible wavelength spectrum (1024 samples), and rapid operation (less than ten hours for complete measurement of an isotropic sample). The gonioreflectometer employs a broadband light source and a detector with a diffraction grating and linear diode array. Validation was achieved by comparisons against reference surfaces and other instruments. The accuracy and spectral and angular ranges of the BRDFs are appropriate for computer graphics imagery, while reciprocity and energy conservation are preserved. Measured BRDFs on rough aluminum, metallic silver automotive paint, and a glossy yellow paint are reported, and an example rendered automotive image is included

Bis(μ2-2-amino-5-nitro­benzoato)bis­(2-amino-5-nitro­benzoato)octa­butyldi-μ3-oxido-tetra­tin(IV)

In the title complex, [Sn4(C4H9)8(C7H5N2O4)4O2], all four SnIV atoms are five-coordinated with distorted trigonal–bipyramidal SnC2O3 geometries. Two SnIV atoms are coordin­ated by two butyl groups, one benzoate O atom and two bridging O atoms, whereas the other two SnIV atoms are coordinated by two butyl groups, two benzoate O atoms and a bridging O atom. All the butyl groups are equatorial with respect to the SnO3 trigonal plane. In the crystal, mol­ecules are linked into a two-dimensional layer parallel to the ab plane by inter­molecular N—H⋯O and C—H⋯O hydrogen bonds and further stabilized by a π–π inter­action [centroid–centroid distance = 3.6489 (11) Å]. Intra­molecular N—H⋯O and C—H⋯O hydrogen bonds stabilize the mol­ecular structure. Two of the butyl groups are each disordered over two sets of sites with site-occupancy ratios of 0.510 (4):0.490 (4) and 0.860 (5):0.140 (5)

Octa­butylbis[μ2-4-(diethyl­amino)­benzoato-κ2 O:O′]bis­[4-(diethyl­amino)­benzoato-κO]di-μ3-oxido-tetra­tin(IV)

The asymmetric unit of the title complex, [Sn4(C4H9)8(C11H14NO2)4O2], consists of two crystallographically independent half-mol­ecules. The other halves are generated by crystallographic inversion centers. In each tetra­nuclear mol­ecule, both of the two independent Sn atoms are five-coordinated, with distorted trigonal–bipyramidal SnC2O3 geometries. One Sn atom is coordinated by two butyl groups, one O atom of the benzoate anion and two bridging O atoms, whereas the other Sn atom is coordinated by two butyl groups, two O atoms of the benzoate anions and a bridging O atom. All the butyl groups are equatorial with respect to the SnO3 trigonal plane. Weak intra­molecular C—H⋯O hydrogen bonds stabilize the mol­ecular structures. In one mol­ecule, two of the butyl groups and the bridging benzoate anion are each disordered over two positions

A Framework for Realistic Image Synthesis

Our goal is to develop physically based lighting models and perceptually based rendering procedures for computer graphics that will produce synthetic images that are visually and measurably indistinguishable from real-world images. Fidelity of the physical simulation is of primary concern. Our research framework is subdivided into three sub-sections: the local light reflection model, the energy transport simulation, and the visual display algorithms. The first two subsections are physically based, and the last is perceptually based. We emphasize the comparisons between simulations and actual measurements, the difficulties encountered, and the need to utilize the vast amount of psychophysical research already conducted. Future research directions are enumerated. We hope that results of this research will help establish a more fundamental, scientific approach for future rendering algorithms. This presentation describes a chronology of past research in global illumination and how parts of our new system are currently being developed

A Framework for Realistic Image Synthesis

Our goal is to develop physically based lighting models and perceptually based rendering procedures for computer graphics that will produce synthetic images that are visually and measurably indistinguishable from real-world images. Fidelity of the physical simulation is of primary concern. Our research framework is subdivided into three sub-sections: the local light reflection model, the energy transport simulation, and the visual display algorithms. The first two subsections are physically based, and the last is perceptually based. We emphasize the comparisons between simulations and actual measurements, the difficulties encountered, and the need to utilize the vast amount of psychophysical research already conducted. Future research directions are enumerated. We hope that results of this research will help establish a more fundamental, scientific approach for future rendering algorithms. This presentation describes a chronology of past research in global illumination and how parts of our new system are currently being developed