Reliefs as images

We describe how to create relief surfaces whose diffuse reflection approximates given images under known directional illumination. This allows using any surface with a significant diffuse reflection component as an image display. We propose a discrete model for the area in the relief surface that corresponds to a pixel in the desired image. This model introduces the necessary degrees of freedom to overcome theoretical limitations in shape from shading and practical requirements such as stability of the image under changes in viewing condition and limited overall variation in depth. The discrete surface is determined using an iterative least squares optimization. We show several resulting relief surfaces conveying one image for varying lighting directions as well as two images for two specific lighting directions.