Linear Light Source Reflectometry
Linear Light Source Reflectometry
SIGGRAPH 2003 Conference Proceedings
Andrew Gardner     Chris Tchou     Tim Hawkins     Paul Debevec
USC Institute for Creative Technologies



This paper presents a technique for estimating the spatially-varying reflectance properties of a surface based on its appearance during a single pass of a linear light source. By using a linear light rather than a point light source as the illuminant, we are able to reliably observe and estimate the diffuse color, specular color, and specular roughness of each point of the surface. The reflectometry apparatus we use is simple and inexpensive to build, requiring a single direction of motion for the light source and a fixed camera viewpoint. Our model fitting technique first renders a reflectance table of how diffuse and specular reflectance lobes would appear under moving linear light source illumination. Then, for each pixel we compare its series of intensity values to the tabulated reflectance lobes to determine which reflectance model parameters most closely produce the observed reflectance values. Using two passes of the linear light source at different angles, we can also estimate per-pixel surface normals as well as the reflectance parameters. Additionally our system records a per-pixel height map for the object and estimates its per-pixel translucency. We produce real-time renderings of the captured objects using a custom hardware shading algorithm. We apply the technique to a test object exhibiting a variety of materials as well as to an illuminated manuscript with gold lettering. To demonstrate the technique's accuracy, we compare renderings of the captured models to real photographs of the original objects.



SIGGRAPH 2003 Paper:

SIGGRAPH 2003 Video:

SIGGRAPH 2003 Paper Talk Slides:


We have placed three additional example videos online to show various types of objects the Linear Light Source Reflectometer can capture. These used a GPU environmental lighting rendering system developed by Ahhijeet Ghosh during his summer 2003 internship at ICT, and were shown as live demos at Andy Gardner's SIGGRAPH 2003 presentation. The can be downloaded in DivX AVI format by clicking on the following images (each clip is approximately 1 minute in length and range between 6MB and 12MB):

The Linear Light Source we used in the project is available from Street Glow , the leader in Auto-Neon & Performance Lighting.

The Robotics device we used is called the Robotics Invention System 2.0. Further information is available at the Lego Mindstorms site.

For one iteration of LEGO control, I used the excellent development environment Not Quite C to program the motion of our LEGO Mindstorms robotics kit. Not Quite C was invaluable for understanding the operation and latency issues involved with the Robotics Control System. I later switched to the LEGO Mindstorms C SDK which can be found on the Lego Mindstorms site.