Cornell University Program of Computer Graphics
Welcome to our main repository of reflectance data.
Most of our BRDF data were measured using our custom-built
gonioreflectometer. For each pair of incident and reflection
directions, we measured two polarizations. The polarized measurements
are combined into unpolarized data to account for the polarization
bias of the setup. The 1024 original wavelength samples are filtered
down to 65 or 31 wavelengths, with 5 or 10nm intervals between 400 and
700nm. Note that the measurements are noisy at short wavelengths and
for grazing angles, where the signal is weak. For smooth surfaces, the
specular reflection causes a spike in the mirror directions, which is
not necessarily an accurate representation of this peak. |
Some data sets were acquired via our image-based measurement technique, using a digital camera. These datasets containt only red, green, and blue channels; data on source and camera spectra are supplied with each to aid in calibration. In general, the RGB triples do not share geometry, as they are individual sensels in a Bayer array.
Painted SurfacesWe have measured the full BRDF of several painted surfaces. These are divided into several categories:
Data File Formats
Gonioreflectometer DataAll gonioreflectometer data are available in MATLAB binary files. In addition, these data are available in a more readable text format.
We have also calculated tristimulus values in CIE XYZ space from the spectral data; they were calculated for the surface illuminated with a D65 illuminant; this should work well if your monitor is set to a D65 white point. That is to say, an ideal white surface illuminated by a source that is equal in all three channels will result in equal RGB on the monitor.
Finally, we used the XYZ tristimulus values to calculate RGB values for Sony Trinitron phosphors. NOTE: No attempt has been made to fit the BRDF values into the monitor gamut: there are negative values in the RGB files. You must decide what best to do to display the colors on your monitor.
This format is intended to comply with ASTM Standard E1392-96, available from the American Society for Testing and Materials for $20-$30. The important parts of the file are the line starting VARS which lists the variables actually contained in the file: (theta_i,phi_i) for the incident elevation and azimuth angles, respectively, (theta_s,phi_s) for the corresponding exitant (scattering) angles, and the BRDF values at the specified wavelengths. These either are actual measurements at equally-spaced wavelengths or tristimulus values in CIE XYZ space or RGB space for Sony Trinitron phosphors.
NOTE: We have no way to test compliance with the ASTM standard, as we know of no software which reads this format, nor have we found any sample data files. If these files do not comply with the standard, please let us know, as we want to comply with a known standard for storing and disseminating BRDF information.
MathWorks. Many of these data are also available in other formats.
NSF Graphics and Visualization Center.
This program has concluded its affiliations summer 2002.