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Global Illumination Shadow Layers
Author(s) -
Desrichard François,
Vanderhaeghe David,
Paulin Mathias
Publication year - 2019
Publication title -
computer graphics forum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 120
eISSN - 1467-8659
pISSN - 0167-7055
DOI - 10.1111/cgf.13781
Subject(s) - shadow (psychology) , computer science , global illumination , computer vision , computer graphics (images) , compositing , shadow mapping , context (archaeology) , object (grammar) , artificial intelligence , graphics , path tracing , radiance , expression (computer science) , layer (electronics) , image (mathematics) , rendering (computer graphics) , optics , geography , psychology , physics , psychotherapist , programming language , chemistry , archaeology , organic chemistry
Computer graphics artists often resort to compositing to rework light effects in a synthetic image without requiring a new render. Shadows are primary subjects of artistic manipulation as they carry important stylistic information while our perception is tolerant with their editing. In this paper we formalize the notion of global shadow, generalizing direct shadow found in previous work to a global illumination context. We define an object's shadow layer as the difference between two altered renders of the scene. A shadow layer contains the radiance lost on the camera film because of a given object. We translate this definition in the theoretical framework of Monte‐Carlo integration, obtaining a concise expression of the shadow layer. Building on it, we propose a path tracing algorithm that renders both the original image and any number of shadow layers in a single pass: the user may choose to separate shadows on a per‐object and per‐light basis, enabling intuitive and decoupled edits.