Soft Shadow Art

Abstract

Shadow art is a form of sculptural art in which the con guration of lights and sculptures cast 2D shadows for artistic e ect. Previous computational methods for the creation of shadow art assumes a single point light that casts a bitonal shadow with sharp boundary. e goal of our study is to generate grayscale shadows using an area light (or an array of point lights) and multiple layers of occluder cells. e area light source casts so shadows consisting of penumbra and umbra. e penumbra is the region in which only a portion of the light source is obscured by the occluders and the umbra is the region where the light sources are completely blocked by the occluders. Th e key challenge is to nd the arrangement of the occluders such that each pixel in the shadow region gathers light from the partially occluded light source to yield a desired tone level. e problem can be formulated as combinatorial optimization with many binary variables. We present a stochastic algorithm that converges quickly to the target shadow image. Our algorithm generalizes easily to deal with arbitrary lighting and geometry setups. We demonstrate the potential of our system with a number of tonal images and the fabrication of artistic ornaments that cast grayscale shadows.