New methods for the computational fabrication of appearance

Abstract

3D printing has been advancing rapidly with new machines becoming available each year. They can already accurately reproduce an object's shape. However, they are very limited when reproducing the object's appearance. Computational fabrication of appearance is an interesting research direction which seeks to extend the appearance reproduction capabilities of current devices and also to manage their limitations. It can have great impact in a number of different fields including product prototyping and design, realistic prosthesis and watermarks in security. This thesis presents three appearance fabrication works: a similarity metric, a light routing algorithm and reflectance fabrication process.

First, recent spatially varying reflectance (svBRDF) printing systems can reproduce an input document as a combination of matte, glossy and metallic inks. Due to the limited number of inks, this reproduction process incurs some distortion. To preserve a material's perceived variation with lighting and view, we introduce an improved BRDF similarity metric that builds on both experimental results on reflectance perception and on the statistics of natural lighting environments. We validate it quantitatively as well as through a perceptual study. We also show how to adapt traditional color gamut mapping methods to svBRDFs to preserve textures and edges.

Second, we use multi-material 3D printing to fabricate objects with embedded optical fibers, exploiting total internal reflection to guide light inside an object. We introduce automatic fiber design algorithms together with new manufacturing techniques to route light between two arbitrary surfaces. Our implicit algorithm optimizes light transmission by minimizing fiber curvature and maximizing fiber separation while respecting manufacturing constraints. Our methods enables new applications in sensing and display such as surface displays of arbitrary shape.

Third, existing BRDF fabrication methods are restricted to using pigments with isotropic light scattering. We propose the use of magnetic reflective pigments such that we can control their orientation by applying a magnetic field. We show how dynamic magnetic fields let us control not only off-specular lobes direction but also lobe width and anisotropy. We show how this magnetic control can be coupled with a projector to fabricate spatially-varying anisotropic BRDFs.