Ústav přístrojové a řídicí techniky

Portable Light Stage for Accurate BTF Measurement on Site (BINGO)

About project

The BINGO project (BTF IN-situ GOnimeteters) is a joint project of the Faculty of Electrical Engineering of the Czech Technical University – Department of Computer Graphics and Interaction and the Faculty of Mechanical Engineering of the Czech Technical University – Department of Precision Mechanics and Optics of the Department of Instrumentation and Control Engineering. To achieve a realistic appearance of digitally created 3D objects, it is necessary to faithfully simulate their surface.

The visual perception of a surface is generally dependent on the direction from which the object is observed, the direction from which the object is illuminated, and the spectrum of the incident light. For one point of the surface, this perception can be quantified as reflectivity – a five-parameter function (2 parameters for the direction of observation, 2 for the direction of illumination and one for the wavelength). However, such a description fails to capture information about the texture of the surface, or surface and subsurface phenomena of the interaction of light with the material, which often have a major impact on the reflectivity and thus the appearance of the surface of the material. Therefore, the bidirectional texture function – BTF is measured: a seven-parameter characteristic including the surface area. BTF is measured as a discrete function and corresponds to many thousands of images of the surface, each taken under a different direction of illumination and a different direction of view of the measured surface.

INVESTIGATORS

Havran, Vlastimil, prof. Ing., Ph.D., Hošek, Jan, doc. Ing., Ph.D., Čáp, Jiří, Ing., Ph.D., Němcová, Šárka, Ing. Bc., Ph.D.

RESULTS

A unique device – Lightdrum – for mobile acquisition of BTF data was developed. More info can be found here https://dcgi.fel.cvut.cz/projects/lightdrum/cz/ grant č. GA14–19213S

EXAMPLES

Model and functional prototype Lightdrum
Application of the measured appearance on various objects