title: Analytic Approximations for Real-Time Area Light Shading.
abstract: We introduce analytic approximations for accurate real-time rendering of surfaces lit by non-occluded area light sources. Our solution leverages the Irradiance Tensors developed by Arvo for the shading of Phong surfaces lit by a polygonal light source. Using a reformulation of the 1D boundary edge integral, we develop a general framework for approximating and evaluating the integral in constant time using simple peak shape functions. To overcome the Phong restriction, we propose a low cost edge splitting strategy that accounts for the spherical warp introduced by the half vector parametrization. Thanks to this novel extension, we accurately approximate common microfacet BRDFs, providing a practical method producing specular stretches that closely match the ground truth in real-time. Finally, using the same approximation framework, we introduce support for spherical and disc area light sources, based on an original polygon spinning method supporting non-uniform scaling operations and horizon clipping. Implemented on a GPU, our method achieves real-time performances without any assumption on area light shape nor surface roughness.
authors.forename: Pascal
authors.initials: P
authors.lastname: Lecocq
authors.forename: Arthur
authors.initials: A
authors.lastname: Dufay
authors.forename: Gael
authors.initials: G
authors.lastname: Sourimant
authors.forename: Jean-Eudes
authors.initials: JE
authors.lastname: Marvie