We present a method for practical physical reproduction and design of homogeneous materials with desired subsurface scattering. Our process uses a collection of different pigments that can be suspended in a clear base material. Our goal is to determine pigment concentrations that best reproduce the appearance and subsurface scattering of a given target material. In order to achieve this task we first fabricate a collection of material samples composed of known mixtures of the available pigments with the base material. We then acquire their reflectance profiles using a custom-built measurement device. We use the same device to measure the reflectance profile of a target material. Based on the database of mappings from pigment concentrations to reflectance profiles, we use an optimization process to compute the concentration of pigments to best replicate the target material appearance. We demonstrate the practicality of our method by reproducing a variety of different translucent materials. We also present a tool that allows the user to explore the range of achievable appearances for a given set of pigments.

Abstract State‐of‐the‐art density estimation methods for rendering participating media rely on a dense photon representation of the radiance distribution within a scene. A critical bottleneck of such kernel‐based approaches is the excessive number of photons that are required in practice to resolve fine illumination details, while controlling the amount of noise. In this paper, we propose a parametric density estimation technique that represents radiance using a hierarchical Gaussian mixture. We efficiently obtain the coefficients of this mixture using a progressive and accelerated form of the Expectation‐Maximization algorithm. After this step, we are able to create noise‐free renderings of high‐frequency illumination using only a few thousand Gaussian terms, where millions of photons are traditionally required. Temporal coherence is trivially supported within this framework, and the compact footprint is also useful in the context of real‐time visualization. We demonstrate a hierarchical ray tracing‐based implementation, as well as a fast splatting approach that can interactively render animated volume caustics.

Computational highlight holography converts three-dimensional computer models into mechanical "holograms" fabricated on (specular) reflective or refractive materials. The surface consists of small grooves with patches of paraboloids or hyperboloids, each of which produces a highlight when illuminated by a directional light. Each highlight appears in different places for different view directions, with the correct binocular and motion parallax corresponding to a virtual 3D point position. Our computational pipeline begins with a 3D model and desired view position, samples the model to generate points that depict its features accurately, and computes a maximal set of non-overlapping patches to be embedded in the surface. We provide a preview of the hologram for the user, then fabricate the surface using a computer-controlled engraving machine. We show a variety of different fabricated holograms: reflective, transmissive, and holograms with color and proper shading. We also present extensions to stationary and animated 2D stippled images.