Database Organization 

Name Convention

• tvBTF09-config.txt
This file saves some information of the path of the files, the number of time steps, the size of the images, and so on. It is used to process the data. It is extracted from tvBTF09-info.txt.


• tvBTF09-time.txt
This file has the time information of each time step when we did the measurement. It is extracted from tvBTF09-info.txt


• tvBTF09-info.txt
This file describes more information regarding the sample scan:

1) Texture Size
2) Exposure used
3) Spectralon sample used for normalization
4) Scan setting as seen from the SphereControl dome program
5) Time stamp of each interval

• btfInfo/
This folder has the information of the coordinates (2D and 3D) of the points on the sample. For example, the resolution of the images in tvBTF09 is 512x512. That means there are 512x512 points on the sample. The 3D coordinates of these points can be found in the file btfInfo/texturePoints3d.txt, and the 2D coordinates of these points from each of the 16 views can be found at btfInfo/texturePoints2d_xx.txt, where xx is the id of the view from 00 to 15.


• raw/
This folder has the measurements (raw data) of this sample. As mentioned, due to the space limitation, we only provided 6 measurements (1 view and 6 lighting directions) at each time step. The name convention is as follows:

norm_btf_LLL_VV_t_TT.exr
where LLL is the light index (from 000 to 149), VV is the view index (from 00 to 15, see here for an explaination of the dome), and TT is the time index (form 00 to the time steps recorded for this sample).  The image is in the EXR format. This is a format for HDR (high dynamic range) image. Please refer here for the information of this format)

The raw data can be used in various ways. For example, in the BRDF fitting phase which will be explained right below, we do feel that neither the BRDF model we used nor the fitting method is perfect, especially for the specular parameters. One could try to use other types of BRDF models (e.g. Oren-Nayar + Full Torrance-Sparrow or Anisotropic Model), or other more robust fitting algorithm with these raw data.


• TSparamNew/
This folder has the fitted BRDF parameters at each time step for this sample. In our work, the BRDF model we used is defined as follows:




where there are 5 parameters: 3 for Kd (R,G,B), 1 for Ks, and 1 for Sigma. So at each time step, we have 3 EXR images to represent these parameters:
• tvBTF09-TT-xx-TSparam-Kd.exr
• tvBTF09-TT-xx-TSparam-Ks.exr
• tvBTF09-TT-xx-TSparam-Sigma.exr
where TT is the time index. The first one is a color image with R/G/B three channels for Kd. The other two are grey level images for Ks and Sigma, respectively.


• SIM/
This folder has the STAF model results. The STAF model we proposed is defined as follows:





In this model, p(x,y,t) is one of the 5 BRDF parameters we have already fitted, and the variables in this model are the following 4 textures and 1 curve:

• A(x,y): the scale factor in the amplitude axis
• B(x,y): the scale factor in the time axis
• C(x,y): the offset factor in the time axis
• D(x,y): the offset factor in the amplitude axis
• \phi(t):  the overall temporal curve

For each of the 5 BRDF parameters, we did the above STAF factorization. The results, for example, for the Kd parameters, are saved in the following files under this directory:

• tvBTF09-staf-Kd-A.exr
• tvBTF09-staf-Kd-B.exr
• tvBTF09-staf-Kd-C.exr
• tvBTF09-staf-Kd-D.exr
• tvBTF09-staf-Kd-phi.txt
The 4 texture images are easy to understand. For the txt file for the curve \phi(t), for each curve we listed the name of the curve, the points on the curves, the order of the polynomial used to fit the curve, the bandwidth of the kernel. Then the followed two lines are the values of the points on the curves, at the time-axis and the amplitude-axis, respectively. The last line is the polynomial fitting results. For example, the curve of Kd in the red channel looks like:
Red
#point 100 #polynomial 7 bopt_r 0.065215

strav_t_r: -0.121077 -0.108424 -0.095770 ......

strav_r: 0.807958 0.790653 0.772969 ......
 
pphi_r: 16.695722 -52.611800 58.813562 -26.188925 3.397970 -0.657741 0.635968 
We also included a figure to show these curves. For example, the R/G/B curves for Kd looks like this.

Our implementation of the algorithm (in Matlab) to estimate the STAF model can be downloaded here (151KB).

Note that there are few samples that can not get robust STAF factorization either for the specular BRDF parameters (Ks and Sigma), or for all the BRDF parameters The possible reasons are as follows:

• The BRDF fitting for the specular parameters is not accurate.
• The specularity is almost zero for these samples.
• There are no obvious time variation in the appearance (i.e. the appearance remains almost constant over time).

Below is the list of these samples:
• No STAF for Ks/Sigma:  tvBTF20, tvBTF28, tvBTF38, tvBTF43
• No STAF:  tvBTF34

Image Format