[talks] Thiago Pereira will present his pre-FPO 11/25/14 at 10am in rm 402

[Nicki Gotsis]

Thiago Pereira will present his Pre-FPO on Tuesday, November 25, 2014 at 10am in rm 402.

The members of his committee is Szymon Rusinkiewicz (advisor), Wojciech Matusik and Tom Funkhouser (readers), Adam Finkelstein and Jianxiong Xiao (non readers).

Everyone is invited to attend his talk.  The talk title and abstract follow below:

"New methods for the computational fabrication of appearance"

	Computational fabrication of appearance is an exciting and challenging new research direction. Its objective is creating objects that interact with light in a manner prescribed in a computational model. It can have great impact in a number of different fields including product prototyping and design, medical applications such as realistic prosthesis, lighting interior environments in architecture and watermarks in security. In this thesis, we propose three works on appearance fabrication: an appearance similarity metric, a light routing algorithm and new 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. In this work, we present an svBRDF gamut mapping algorithm that minimizes distortions in the angular and spatial domains. 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. Our experiments show better preservation of object color and highlights, as validated quantitatively as well as through a perceptual study. As for the spatial domain, we show how to adapt traditional color gamut mapping methods to svBRDFs. Our solution takes into account the contrast between regions, achieving better preservation of textures and edges.

	Second, despite recent interest in digital fabrication, there are still few algorithms that provide control over how light propagates inside a solid object. Existing methods either work only on the surface or restrict themselves to light diffusion in volumes. 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 constraints such as fiber arrival angle. We also discuss the influence of different printable materials and fiber geometry on light propagation in the volume and the light angular distribution when exiting the fiber. Our methods enable new applications such as surface displays of arbitrary shape, touch-based painting of surfaces and sensing a hemispherical light distribution in a single shot.

	Third, existing BRDF fabrication methods still have many limitations such as: symmetry of light scattering or restriction to small scattering angles. We propose to use magnetic reflective pigments such that we can control their orientation by applying a magnetic field. We use dynamic magnetic fields for controlling 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 achieve new spatially-varying anisotropic BRDFs.