Laurent Noël

Optimisation of selective alkaline extraction for Cr(VI) determination in dairy and cereal products by HPIC-ICPMS using an experimental design.

This study presents the optimisation through an experimental design then the validation of a method to determine Cr(VI) in certain foodstuffs by high-performance ionic chromatography with inductively coupled plasma mass spectrometry. This method is free from interferences possibly associated with chloride and organic or inorganic carbon. Analytical performances assessed by the accuracy profile method were satisfactory in terms of linearity, specificity, sensitivity, accuracy, repeatability and intermediate precision. Limits of quantification ranged from 0.6μg.kg(-1) in dairy products to 0.8μg.kg(-1) in cereal products. The method was applied to the determination of Cr(VI) in dairy and cereal products from different brands and origins. Despite the methods very high sensitivity, Cr(VI) was not found in all the studied samples. This confirms the results of the most recent studies using an on-line speciation method, and invalidates older studies that found traces of Cr(VI) in food by using a less specific off-line speciation method.

Mercury in foods from the first French total diet study on infants and toddlers

A very sensitive method using a direct mercury analyser was developed and validated according to the accuracy profile procedure to determine mercury levels in foods mainly consumed by infants and toddlers. Total mercury was not detected (LOD of 0.30µg.kg-1 fresh weight) in 92.4% of the 291 food samples analysed or at relatively low concentrations, lesser than or equal to LB/UB 0.5/1.0µg.kg-1 in all samples, except in fish samples (mean LB/UB 25µg.kg-1 with a maximum of 53µg.kg-1). Levels of total mercury in these foods were in all cases within permitted Regulatory limits of 500 or 1000µg.kg-1 in fishery products and muscle meat of fish.

A 3d curvilinear skeletonization algorithm with application to path tracing

We present a novel 3D curvilinear skeletonization algorithm which produces filtered skeletons without needing any user input, thanks to a new parallel algorithm based on the cubical complex framework. These skeletons are used in a modified path tracing algorithm in order to produce less noisy images in less time than the classical approach.

Coarse irradiance estimation using curvilinear skeleton

Light flux can take complex paths to reach the observer, especially in large and sophisticated scenes. In such situations, global illumination algorithms are used: irradiance caching, path tracing and radiosity allow to precisely compute the irradiance at any point of the scene, but remain quite slow. Our present work aims to evaluate, very coarsely, the irradiance of any point of a scene, allowing to give global illumination algorithms some information about the main direction and intensity of the light flux. We use a coarse representation of the scene using a skeleton of its voids (where the light propagates). We present two heuristics to compute a coarse radiance estimation and the main light stream orientation. Our work gives the possibility to define many other heuristics.

Denoising at scale for massive animated series

In the modern era of physically-based shading, removing the substantial amount of high frequency noise produced by Monte Carlo rendering techniques is a key challenge for production renderers. Beyond the recent advances in sample-based and feature-based denoising, production constraints and scale introduce additional mandatory features for candidate denoisers. In this talk, we discuss how denoising is deployed in Shining, the production renderer developed by Ubisoft Motion Pictures for the Rabbids Invasion animated TV series. The scale of the show, as well as the required control for artists, led us to the integration of a sample-based denoiser, which enables per-AOV denoising control, with a minimum overhead regarding engine integration and production workflow. As a result, all-effects denoising is made possible for the new TV series season and proved useful in numerous lighting and material scenarios. At the core of the denoising pipeline, our BCD algorithm, recently made open source, provides a robust and fast mechanism to filter out Monte Carlo noise while retaining features, for complex lighting and viewing conditions, with trivial per-AOV setup.

Portal Extraction Based on an Opening Labeling for Ray Tracing

Rendering photo-realistic images from a 3D scene description remains a challenging problem when processing complex geometry exposing many occlusions. In that case, simulating light propagation requires hours to produce a correct image. An opening map can be used to extract information from the geometry of the empty space of a scene, where light travels. It describes local thickness and allows to identify narrow regions that are difficult to traverse with ray tracing. We propose a new method to extract portals in order to improve rendering algorithms based on ray tracing. This method is based on the opening map, which is used to define a labeling of the empty space. Then portals - 2D surfaces embedded in empty space - are extracted from labeled regions. We demonstrate that those portals can be sampled in order to explore the scene efficiently with ray tracing.

Skeleton based Vertex Connection Resampling for Bidirectional Path Tracing

Bidirectional path tracing is known to perform poorly for the rendering of highly occluded scenes. Indeed, the connection strategy between light and eye subpaths does not take into account the visibility factor, presenting no contribution for many sampled paths. To improve the efficiency of bidirectional path tracing, we propose a new method for adaptive resampling of connections between light and eye subpaths. Aiming for this objective, we build discrete probability distributions of light subpaths based on a skeleton of the empty space of the scene. In order to demonstrate the efficiency of our algorithm, we compare our method to both standard bidirectional path tracing and a recent important caching method.

Real-Time Global Illumination for Games using Topological Information

Indirect Illumination is a key element to achieve realistic rendering. Unfortunately, since computing this effect is costly, there are few methods that render it with real-time frame rates. In this paper we present a new method based on virtual point lights and topological information about the scene to render indirect illumination in real-time.