Note 1, 2011: The text was written in 2002, meanwhile (2011) a BRTF,BSDF database is available at: http://www.pab.eu/bme/
Note 2, 2019: Cosmetic overhauled in August 2019: The old server-parsed-html constructs for the data files had been phased out on my server long ago. The text uses the term BRTF (bidirectional-reflection-transmission-function), the more uniformly accepted term is BSDF (bidirectional-scatter-distribution-function), which I conformed to later.
Note 3, 2019: The measurements presented here had been measured in 2002 with my old and first gonio-photometer at Fraunhofer ISE. My second design, the PG2 gonio-photometer, had been started, outside Fraunhofer ISE, then in 2004.
Note 4, 2019: If you read this as PDF, the old data files and images are still available.

Examples

The classical metal model of Radiance was fitted to the BRTF data using standard Levenberg-Marqwardt fitting methods. Gray reflectance (R=G=B for the first three parameters of the model) was assumed. Light source was a XBO short arc lamp.
The incident angle thetain, phiin is encoded into the file name. For pab-xenon-aluA-st1:+15+0.mpc: thetain=15o, phiin=0o .
The following tables give the measured BRTF, their visualization, the parameters RGB, specularity and roughness, and the error (sum of weighted, squared difference between model and data at measured positions).
Visualizations were done using mountain, a custom written program for displaying BRTF measurements done by the above mentioned gonio-photometer. The BRTF of a perfectly diffuse material would show as flat surface. For high values, the measurements are done at finer angular resolution (see my Phd for a discussion on measurement technique). The small gaps in the data are due to self shadowing of the ISE-FhG gonio-photometer.

Aluminium sheet, metal model

photo of pab-xenon-aluA-elox1-b
data file visualization Radiance metal model
  orthogonal oblique RGB,spec,rough fit visualization
      R,G,B spec. rough. error model difference
raw/pab-xenon-aluA-elox1-b:+0+0.mpc 0.891 0.657 0.13 3.6e+03
raw/pab-xenon-aluA-elox1-b:+15+0.mpc 0.877 0.606 0.142 3.5e+02
raw/pab-xenon-aluA-elox1-b:+30+0.mpc 0.878 0.665 0.17 1.7e+02
raw/pab-xenon-aluA-elox1-b:+45+0.mpc 0.893 0.73 0.195 1.4e+02
raw/pab-xenon-aluA-elox1-b:+60+0.mpc 0.878 0.853 0.192 8.9e+02

Sand blasted aluminium sheet, metal model

Aluminium sheet blasted with small glass spheres. More isotropic than raw aluminium sheet, but still showing asymmetric scattering
photo of pab-xenon-aluA-st1-b
data file visualization Radiance metal model
  orthogonal oblique RGB,spec,rough fit visualization
      R,G,B spec. rough. error model difference
raw/pab-xenon-aluA-st1-b:+0+0.mpc 0.624 0.706 0.437 20
raw/pab-xenon-aluA-st1-b:+15+0.mpc 0.857 1 0.497 2.8
raw/pab-xenon-aluA-st1-b:+30+0.mpc 0.937 0.981 0.479 6.7
raw/pab-xenon-aluA-st1-b:+45+0.mpc 1.06 0.999 0.45 21
raw/pab-xenon-aluA-st1-b:+60+0.mpc 1.46 1.15 0.436 2e+02

work-in-progress. Please bear with us while the rest is under construction. Thanks