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Journal Articles Computer Graphics Forum Year : 2019

Global Illumination Shadow Layers


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.
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Format : Figure, Image
Format : Other
Comment : Supplemental materials containing shadow layers and Natron2 projects to reproduce the figures from the paper.

Dates and versions

hal-02174327 , version 1 (05-07-2019)



François Desrichard, David Vanderhaeghe, Mathias Paulin. Global Illumination Shadow Layers. Computer Graphics Forum, 2019, 38 (4), ⟨10.1111/cgf.13781⟩. ⟨hal-02174327⟩
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