Database Organization 

Database Details

• tvBrdf-info.txt
This file contains information about the scanning prodecure for each sample. This includes:

    1) Sample Name (Process)
    2) Exposures used to generate HDR radiance data
    3) Number of scans
    4) Time stamp of each scan
  

• tvBrdf-data/
This folder contains the HDR radiance measurements for the sample. As explained here we average radiance values over a patch of the sample to compute the aggregate BRDF. This is done for three different exposures that are combined to produce the measurements in this folder. The text files here are named

scanTT_brdf_cameraV_allexposures.txt
where TT is the scan index (from 01 to the number of time this sample was scanned), V is the camera index (from 1 to 4, see here for an explanation of the rig).

There are thus number of views (4) X number of scans (sample specific) files in this folder and each file stores the BRDF for all lighting directions. The first line of each file lists the exposures used for the sample. Each set of three lines following this has the radiance values (B G R), the lighting direction (LX LY LZ) and the viewing direction (VX VY VZ). For example for sample01 scan01_brdf_camera1_allexposures.txt looks like


Exposure 0.200000 4.000000 32.000000
F 0.669680 0.778409 0.834711
L 0.978148 0.000000 0.207912
V -0.207912 0.000000 0.978148

This means that the radiance for this sample at lighting direction <0.978148, 0.000000, 0.207912> and viewing direction <-0.207912, 0.000000, 0.978148> the radiance is (0.834711, 0.778409, 0.669680).

These measurements need to be radiometrically calibrated to compensate for both the light source and the camera response. For this we used a spectralon sample with albedo(B, G, R) = (0.7410, 0.7438, 0.752). The radiance measurements for the spectralon sample are here. We fit a Lambertian BRDF model to the radiance measurements of the spectralon and have computed the normalization constants for each camera and each color channel. These can be accessed here. The four lines of this text file have the values (B, G, R) that the radiance measurements from each camera need to be divided by for each color channel.


• tvBrdf-fits/
We have fit analytic BRDF models to our measurements at each time instant. This folder contains the file
brdf-params.txt
Each line of this file has fit parameters for one scan.

For the paint, drying and miscellaneous samples (sample01 - sample27 and sample40 - sample41) we have fit a combination of the Oren-Nayar diffuse BRDF and the Torrance-Sparrow specular BRDF models. For these samples brdf-params.txt has 6 parameters at each time instant. These are, in order K_d(B, G, R), sigma_d, K_s and 1 / sigma_s,

For the dust samples (sample28 - sample39) we have fit a combination of Blinn's Dust BRDF and the Torrance-Sparrow specular BRDF models. For these samples brdf-params.txt has 11 parameters at each time instant. These are, in order K_d(B, G, R), sigma_d, K_s, 1 / sigma_s, w_dust(B, G, R), g and tau

For a detailed explanation of each model and parameter please look at the following paper and its appendices:

The fitted model enables us to directly render the measured materials' appearance over time. The following video shows a teapot rendered with our measurements of the BRDF of blue watercolor on white paper. Note the change in the fit model parameters over time and the resulting change in the appearance.