Precomputed Multiple Scattering for Rapid Light Simulation in Participating Media

International audienceRendering translucent materials is costly: light transport algorithms need to simulate a large number of scattering events inside the material before reaching convergence. The cost is especially high for materials with a large albedo or a small mean-free-path, where higher-order scattering effects dominate. We present a new method for fast computation of global illumination with participating media. Our method uses precomputed multiple scattering effects, stored in two compact tables. These precomputed multiple scattering tables are easy to integrate with any illumination simulation algorithm. We give examples for virtual ray lights (VRL), photon mapping with beams and paths (UPBP), Metropolis Light Transport with Manifold Exploration (MEMLT). The original algorithms are in charge of low-order scattering, combined with multiple scattering computed using our table. Our results show significant improvements in convergence speed and memory costs, with negligible impact on accuracy

A Compact Representation for Multiple Scattering in Participating Media using Neural Networks

International audienceMany materials, such as milk or wax, exhibit scattering effects; incoming light enters the material and is scattered inside, giving a translucent aspect. These effects are computationally intensive as they require simulating a large number of events. Full computations are expensive, even with accelerating methods such as Virtual Ray Lights. We present a method to encode multiple scattering effects using a neural network. We replace the precomputed multiple scattering table with a trained neural network, with a cost of 6490 bytes (1623 floats). At runtime, the neural network is used to generate multiple scattering. We demonstrate the effects combined with Virtual Ray Lights (VRL), but our approach can be integrated with other rendering algorithms

Interactive Simulation of Scattering Effects in Participating Media Using a Neural Network Model

International audienceRendering participating media is important to the creation of photorealistic images. Participating media has a translucent aspect that comes from light being scattered inside the material. For materials with a small mean-free-path (mfp), multiple scattering effects dominate. Simulating these effects is computationally intensive, as it requires tracking a large number of scattering events inside the material. Existing approaches precompute multiple scattering events inside the material and store the results in a table. During rendering time, this table is used to compute the scattering effects. While these methods are faster than explicit scattering computation, they incur higher storage costs. In this paper, we present a new representation for double and multiple scattering effects that uses a neural network model. The scattering response from all homogeneous participating media is encoded into a neural network in a preprocessing step. At run time, the neural network is then used to predict the double and multiple scattering effects. We demonstrate the effects combined with Virtual Ray Lights (VRL), although our approach can be integrated with other rendering algorithms. Our algorithm is implemented on GPU. Double and multiple scattering effects for the entire participating media space are encoded using only 23.6 KB of memory. Our method achieves 50 ms per frame in typical scenes and provides results almost identical to the reference

Magmatic Au mineralization at the Bilihe Au deposit, China

Most known primary Au deposits are produced by hydrothermal processes. In this paper, we report Au mineralization of magmatic origin in the Bilihe deposit, China (8.5 Mt averaging 2.9 g/t Au). At Bilihe, most (>70%) native Au (no detectable Ag) grains are euhedral or subspherical in shape, and occur as trails in dendritic quartz phenocrysts and comb-layered quartz in a moderately reduced, highly fractionated diorite-granite intrusion. The hosting quartz typically has a dendritic core (Q1) and a rim (Q2), with Q1 having concentric zoning and sector zoning in cathodoluminescence (CL) images. Cathodoluminescence petrography and crystallographic modeling reveal that most of the Au trails occur along intersecting crystallographic planes of the host quartz, indicating simultaneous precipitation of both Au and quartz. Abundant melt inclusions are present in Q2 with >950°C homogenization temperatures. Minor Au grains also occur in melt inclusions in quartz. In rare cases, necking of Au melt inclusions is present. Neither Q1 nor Q2 contain primary fluid inclusions; only secondary fluid inclusions were found in healed cracks. The above observations indicate a direct magmatic (quartz phenocryst phase) origin for the Au. This defines a new type of Au deposit, and thereby opens new potential for Au exploration. The magmatic origin of Au at Bilihe also implies that enrichment of Au may occur in a source melt prior to volatile escape, which would enhance the possibility of forming a magmatic-hydrothermal Au deposit

Zircon U–Pb dating, geochemistry and Sr–Nd–Pb–Hf–O isotopes for the Nan'getan granodiorites and mafic microgranular enclaves in the East Kunlun Orogen: record of closure of the Paleo-Tethys

The East Kunlun Orogen in the Northern Qinghai–Tibet Plateau is an ideal region to investigate the geodynamic processes of magmatism related to the closure of the Paleo-Tethys Ocean. Here, we report petrology, zircon U–Pb geochronology, whole-rock geochemistry and multiple isotope data from granodiorites and the associated dioritic enclaves in a dominant Nan'getan granitoid in the East Kunlun Orogen. Zircon U–Pb ages indicate that the host granodiorites and dioritic enclaves were synchronously emplaced at ~243 Ma. The granodiorites are medium- to high-K calc-alkaline, metaluminous (A/CNK = 0.93–0.98), with high Al(2)O(3) content (15.28%–16.10%), Mg# (47–49), very low Sr/Y ratios (127–217), high abundances of incompatible elements (Y = 3.87–8.36 ppm, Nb = 3.04–5.71 ppm, Th = 3.04–5.71 ppm), low (87Sr/86Sr)i (0.7050–0.7079), negative whole-rock εNd(t) (− 8.2 to − 5.8), (206Pb/204Pb) 243Ma of 18.520 to 18.772, (207Pb/204Pb) 243Ma of 15.611 to 15.650, (208Pb/204Pb) 243Ma of 38.227 to 38.528, δ18OSMOW = 6.8‰–9.1‰, εHf(t) of − 1.2 to + 2.4. The dioritic enclaves (SiO(2) = 51.08%–56.29%) have Mg# values of 48–51, with negative Eu anomalies (δEu = 0.59–0.79), low (87Sr/86Sr)i (0.7058–0.7080), negative whole-rock εNd(t) (− 8.2 to − 5.8), (206Pb/204Pb) 243Ma of 18.376 to 18.809, (207Pb/204Pb)243Ma of 15.606 to 15.661, (208Pb/204Pb)243Ma of 38.244 to 38.540, δ18OSMOW = 5.6‰–10.0‰, εHf(t) of − 3.5 to + 1.7. These isotopic features of arc-type rocks from the East Kunlun suggest that the parental magmas of the Nan'getan granodiorites and the dioritic enclaves originated from an enriched lithospheric mantle. The Nan'getan granitoids might have recorded the northward subduction of the Paleo-Tethys ocean lithosphere following the initial collision of the Bayan Har–Songpan Ganzi–East Kunlun terrane and the closure of the Paleo-Tethys Ocean at ~243 Ma

Molybdenite Re–Os, zircon U–Pb dating and Hf isotopic analysis of the Shuangqing Fe–Pb–Zn–Cu skarn deposit, East Kunlun Mountains, Qinghai Province, China

The Shuangqing Fe–Pb–Zn–Cu deposit is located in the Xiangride County of Qinghai Province, China, and is a typical example of skarn deposits in the East Kunlun Mountains. Skarnization and mineralization took place along the contact zone between Carboniferous carbonates and the concealed Triassic plagiogranite. LA–ICP–MS U–Pb dating of zircons from the plagiogranite has yielded ages of 227.2 ± 1.0 and 226.54 ± 0.97 Ma, which are interpreted as the emplacement age of the plagiogranite. Molybdenites separated from ore-bearing quartz-veins yielded a Re–Os isochron age of 226.5 ± 5.1 Ma. These age data confirm that both intrusion and related skarn mineralization initiated at ~ 227 Ma. Re contents of molybdenite, zircon εHf(t) and (176)Hf/(177)Hf values fall into the ranges 3.31 to 6.58 μg/g, − 8.6 to − 0.0, and 0.282403 to 0.28263850, respectively. The timing of the Shuangqing Fe–Pb–Zn–Cu mineralization coincided with a major change in the stress field in East Kunlun from transpression to extension, related to the partial melting of thickening crustal materials in a post-collisional tectonic setting

Novel tetraarylsilane-based hosts for blue phosphorescent organic light-emitting diodes

Two highly twisted tetraarylsilane derivatives containing carbazole and benzimidazole were designed and synthesized with high triplet energy level (E-T) as hosts for blue phosphorescent organic light-emitting diodes (PHOLEDs). The thermal, photophysical, electrochemical properties and geometry optimization of materials were studied. The central silicon atom effectively disconnected the electronic interactions among the three functional units in a molecule, resulting in high E-T and relatively wide band gap (E-g) (>= 3.5 eV). Finally, the blue PHOLED devices using 3,3'-((phenyl(4-(9-phenyl-9H-carbazol-2-yl)phenyl)silanediyl)bis(4,1-phenylene)) bis(9-phenyl-9H-carbazole) (TCzSi) as host material achieved a maximum current efficiency of 25.5 cd A(-1), a maximum power efficiency of 18.15 lm W-1, a maximum luminance of 6285 cd m(-2) and a maximum external quantum efficiency (EQE) of 13.32%. This study showed a molecular design strategy to develop novel tetra-arylsilane-based compounds for blue hosts