Pascal Lecocq

Computer Graphics Researcher... mostly in real-time rendering

Current company: Technicolor

Contact: pascal(dot)lecocq(at)gmail(dot)com

Publications


Area Light TVCG 2017

Analytic Approximations for Real-Time Area Light Shading

Pascal Lecocq*,  Arthur Dufay, Gaël Sourimant, Jean-Eudes Marvie
To appear in IEEE TVCG 2017

This paper is the extended version of our real-time area light research presented at ACM I3D 2016. As main novelty, we derive approximation for the integral product of Cosine Lobes, providing suppport for more complex BRDFs expressions. The microfacet section has been also extended with additional results and a discussion about the limitations of the edge-splitting strategy. To overcome some of the limitations, we propose a balancing heuristic that better controls the split position and better matches the distortions introduced by the half-space transform. Finally, the spherical and disc area light section has been largely extended with detailed algorithms, comparisons, and a discussion about the limitations.

[pdf] [video I3D2016] [bib]
Sub-Pixel Shadow Maps

Cache-Friendly Micro-Jittered Sampling

Arthur Dufay*,  Pascal Lecocq*,  Romain Pacanowski,  Jean-Eudes Marvie,  Xavier Granier
*Joint first Authors  -  in SIGGRAPH 2016 Talks

We introduce a cache-friendly micro-jittered technique for faster multi-dimensional Monte-Carlo integration in parallel ray-tracing engines. The method improves ray coherency and cache efficiency between GPU threads using a slightly altered random sequence rather than using ray-reordering methods. Our method is simple, compatible with any low-discrepancy sequences, and can drastically reduce rendering times of GPU/CPU path-tracers or any stochastic ray-based renderers.

[pdf] [video] [bib]
Specular Area Lighting

Accurate Analytic Approximations for Real-Time Specular Area Lighting

Pascal Lecocq,   Arthur Dufay,   Gaël Sourimant,   Jean-Eudes Marvie
In proceedings of ACM SIGGRAPH i3D 2016,

Best Paper award by paper chairs, Best Presentation award by votes from conference attendees.

This paper is the detailed version of the SIGGRAPH talk presented in 2015 with several extensions. Main contibutions are: a general framework for approximating and evaluating the edge integrals in O(1) time instead of O(n) using simple and integrable peak shape functions. A low-cost edge splitting strategy for handling the warp distortion introduced by the half vector parameterization that preserves the highlight shape of microfacet BRDF. An original spinning algorithm enabling spherical and disc area lighting that benefits from our approximations and supports non-uniform scale operations. Timings on recent GPU available in additional notes.

[pdf] [video stream] [video] [bib] [additional notes] [slides pptx + error analysis]
Specular Area Lighting

Accurate Analytic Approximations for Real-Time Specular Area Lighting

Pascal Lecocq, Gaël Sourimant, Jean-Eudes Marvie
In SIGGRAPH 2015 Talks

We introduce analytic approximations for accurate real-time rendering of specular surfaces illuminated by polygonal light sources. Our solution is based on a reformulation of the contour integral [Arvo 1995] we approximate analytically with simple peak functions. In addition, using simple geometric operations, we extend the solution to handle the half-vector transform and represent more physically plausible BRDF. Our solution works without any assumption on light source shape nor surface roughness, bringing real-time performances with a quality close to the ground truth.

[pdf] [video] [bib]
Sub-Pixel Shadow Maps

Sub-Pixel Shadow Mapping

Pascal Lecocq, Jean-Eudes Marvie, Gaël Sourimant, Pascal Gautron
In Proceedings of ACM I3D 2014

Sub-pixel shadow maps are an alternative to the conventional shadow mapping technique allowing the real-time rendering of "near" alias-free shadows with strong temporal consistency. Our technique is based on the storage of a fixed-size partial representation of the scene geometry using conservative rasterization. Combined with an original reconstruction of shadow edges, our method avoids both perspective and projection aliasing with only a small computational overhead.

[pdf] [video] [bib]
Boundary-Aware Extinction Mapping

Boundary-Aware Extinction Mapping

Pascal Gautron, Cyril Delalandre, Jean-Eudes Marvie, Pascal Lecocq
In proceedings of Pacific Graphics 2013

Boundary-Aware Extinction Maps targets interactive rendering of massive heterogeneous volumetric datasets. Our approach is based on the projection of the extinction along light rays into a boundary-aware function space, focusing on the most relevant sections of the light paths. This technique also provides an alternative representation of the set of participating media, allowing scattering simulation methods to be applied on arbitrary volume representations.

[pdf] [video] [bib]
Sub-Pixel Shadow Maps

Sub-Pixel Shadow Mapping

Pascal Lecocq, Pascal Gautron, Jean-Eudes Marvie, Gaël Sourimant
In SIGGRAPH 2013 Talks

Sub-pixel shadow maps are an alternative to the conventional shadow mapping technique allowing the real-time rendering of "near" alias-free shadows with strong temporal consistency. Our technique is based on the storage of a fixed-size partial representation of the scene geometry using conservative rasterization. Combined with an original reconstruction of shadow edges, our method avoids both perspective and projection aliasing with only a small computational overhead.

[pdf] [video] [bib]
Volume Aware

Volume-Aware Extinction Mapping

Pascal Gautron, Cyril Delalandre, Jean-Eudes Marvie, Pascal Lecocq
In SIGGRAPH 2012 Talks

The Volume-Aware Extinction Maps accounts for multiple animated participating media, without assumptions on their relative positions and nature. The approach is based on the projection of the extinction function along light rays into a volume-aware functional space, concentrating the representation accuracy within the most relevant sections of the light paths. We demonstrate the use of our technique for interactive editing and navigation in complex volumetric scenes using a simple out-of-core rendering framework, making VAEM valuable tools for real-time rendering applications as well as production pre-visualization.

[pdf] [video] [bib]
muw

Streaming and Synchronization of Multi-User Worlds Through HTTP/1.1

Jean-Eudes Marvie, Pascal Gautron, Pascal Lecocq, Olivier Mocquart, François Gérard
In Proceedings of ACM Web3D 2011

We propose an approach for adaptive streaming of on-line multi-user virtual worlds, using generic transfer protocols and a unified representation of the worlds usable on an arbitrary wide range of platforms. HTTP/1.1 natively supports two crucial features for data streaming: persistent connections and chunked access to files. Based on those simple capabilities we propose unified representations of arbitrarily large virtual worlds based on X3D, as well as methods for adaptive streaming and interaction regardless of the network bandwidth or capabilities of the client hardware.

[pdf] [video] [bib]

Assessment of the Simulation of Low Beams Back-Scattering in Fog

Dumont E., Paulmier G., Lecocq P., Kemeny A
6th International Symposium on Automotive Lighting, ISAL 2005

In this paper, we address the backscattered veil caused by low beam headlamps in fog. We use a computational approach, based on a Monte Carlo light tracing technique which allows us to compute the backscattered luminance distribution in the driver’s field of vision. We investigate several hypotheses (far field photometry, single scattering, and absence of volume shadows). We examine the influence of these approximations on the average backscattered luminance in a 20° solid angle for various fog conditions, and draw conclusions concerning their validity for a particular set of headlamps. .

[link to the paper]

Integration of AFS-functionality into driving simulators

Rudolf B., Schmidt J., Grimm M., Kalze F.-J., Wördenweber B., Lecocq. P., Kemeny A., Panerai F.
Proceedings of the Driving Simulation Conference, DSC 2004

Around 55,000 people are killed each year in accidents throughout the European Community. Night- time driving with conventional headlamps is particularly unsafe: only 25% of the driving is done at night but 55% of the driving fatalities occur during this period. In order to reduce these figures, new automotive lighting technologies (Advanced Front Lighting System AFS) are about to be permitted in ECE legislation. This paper presents both, integration of pre- and full AFS into a driving simulator considering constraints such as the accuracy of photometric data, the integration of AFS control strategies in a driving simulation loop and realistic real-time rendering.

[pdf]

Lighting Simulation With the Presence of Fog: a Real-Time Rendering Solution For Driving Simulators

Pascal Lecocq, Sylvain Michelin, Andras Kemeny, Didier Arquès
Proceedings of the Driving Simulation Conference, DSC 2002

Driving simulators are increasingly used to assess healdlight design prior to their conception thanks to the introduction of interactive headlight simulation tools. Although, by assuming clear weather conditions, these solutions fail to early detect the presence of potentially disturbing light shafts occuring under foggy weather condition. This paper introduces a real-time rendering technique allowing proper representation of such light shafts, suitable for driving simulators. The solution relies on mathematical reformulation and approximation of the light transport equation combined with a screen space rendering technique for real-time efficiency. Implemented on a driving simulator, our solution can be applied for the oncoming traffic headlights as well as for driver’s headlight.

[pdf] [video from my PhD defense (2001)]

Mathematical Approximation for Real-Time Lighting Rendering Through Participating Media

Pascal Lecocq, Andras Kemeny, Sylvain Michelin, Didier Arquès
Proceedings of the 8th Pacific Conference on Computer Graphics and Applications, PG 2000

Many shading models are able to provide realistic rendering of lighting effects under various atmospheric conditions but computational times are often expensive. This paper proposes a method to render lighting effects within participating media in real-time on a graphics workstation. It consists of mathematical approximations based on a re-formulation of the light transport equation considering atmospheric scattering with light sources described by their luminous intensity distribution. The proposed approximations allow constant-time evaluation of the air-light integral and use graphics hardware capabilities of workstations to accelerate parts of the rendering process.

[pdf] [bib]

Interactive Headlight Simulation

Pascal Lecocq, Jean-Marc Kelada, Andras Kemeny
Proceedings of the Driving Simulation Conference, DSC 1999

This paper introduces the interactive headlight simulation software developed at Renault Research department. The software aims to reduce the cost and delay of headlamp prototyping using virtual headlamp assessment in a driving simulator. Accurate rendering and lighting of the road is achieved in real-time using a photometric description of the headlamp encoded in a texture and a specific level of detail management. During the driving experience, several parameters can be adjusted in real-time, such as the position and the orientation of the headlamps. The headlight simulation software was integrated in Renault’s driving simulators in 1998 and validated by Renault’s photometric laboratory.

[pdf]
more coming soon ...