tvBTF09/ | |||

btfInfo/ | 3d coordinates of the points on the sample | ||

raw/ | 6 measurements at each time step, raw data | ||

TSparamNew/ | fitted BRDF parameters | ||

SIM/ | STAF model parameters | ||

tvBTF09-config.txt | see below | ||

tvBTF09-time.txt | |||

tvBTF09-info.txt |

**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

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.

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**

In this model,

**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**

RedWe also included a figure to show these curves. For example, the R/G/B curves for Kd looks like this.

#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

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**

In our study, I only used it to write a 3-channel float-point value image (for grey level images, the values in the 3 channels are the same), and did not use any fancy features in OpenEXR. I wrote two simple matlab functions to read/write EXR images for this simple usage. Download here (790 KB).

STAF Database Home

Contact: staf@lists.cs.columbia.edu

Last modified: 08/28/2006