This article describes how to install and use the ISX-to-BSDF Converter Tool.
As of Ansys Zemax OpticStudio 23R2, .ISX files are no longer supported. The ISX-to-BSDF converter was developed as a standalone tool to ensure that data in ISX files can be converted into appropriate .BSDF files for use in OpticStudio.
Authored By Dominique Gálvez
Background
Both ISX and BSDF data formats are used to define the scattering properties of surfaces, but their structures differ in a few ways.
.ISX files are generated by an IS-STAM device and produce a binary file that describes the scattering properties of the surface. The .ISX file data is purely monochromatic and carries no photometric weighing information. Previously, the OpticStudio user was able to set the angular resolution of their .ISX data to 1, 2, or 5 degrees when using it in their systems. During the conversion process, 1-degree sampling of the .ISX file is used to ensure a high degree of accuracy between the two files.
.BSDF files are also used to incorporate a surface’s scattering properties into the behavior of the optical system, specifically its Bi-Directional Scatter Distribution Function. The data in .BSDF files is provided in a text format that adheres to the Zemax Tabular .BSDF file format outlined in this article, “Zemax Tabular BSDF data file format – Knowledgebase.” More information on how to use the .BSDF data to define the scattering distribution of a surface is given in another article: “How to use tabular BSDF data to define the surface scattering distribution”
Aside from the differences in file formatting, the .ISX and .BSDF file types support different types of symmetry in the scattering distribution data that must be considered when converting from .ISX to .BSDF. The concepts of sample rotation angle and azimuth angle are explained in the .BSDF file format article Zemax Tabular BSDF data file format.
The .ISX file format supports the following three types of symmetries:
- Isotropic: where measurements are present for a single sample rotation angle.
- Mirror Anisotropic: where measurements are present for multiple sample rotation angles between 0 and 90 degrees (typically 0, 45, and 90 degrees)
- Fully Anisotropic: where measurements are present for multiple sample rotation angles, from 0 to 360 degrees
In comparison, the BSDF files support these three types of symmetries:
- PlaneSymmetrical: measurements are present for a single sample rotation angle and scatter azimuths are only reported between 0 and 180 degrees
- Asymmetrical: measurements are only present for a single sample rotation, and scatter azimuths are reported between 0 and 360 degrees.
- Asymmetrical4D: measurements from multiple sample rotations are present from 0 to 360 degrees, and all scatter azimuths are reported between 0 and 360 also
The converter considers the symmetry type from the ISX file when converting into an appropriate BSDF symmetry format, as shown in the figure below. Note: the single quadrant of data given in the ISX Mirror Anisotropic file is symmetrically expanded out to the full, 360-degree span of sample rotations needed for the BSDF Asymmetrical4D symmetry format.
Installation
To successfully install and run the ISX-to-BSDF converter, the user will need Microsoft Visual C++ runtime 14 and SQL Serve CE 3.5 (64-bit) on their computer. The ISX-to-BSDF installer includes the Visual C++ runtime 14, if the user does not have it already. Users with a previous version (pre OpticStudio 2023 R2) of OpticStudio installed will already possess SQL Serve CE 3.5, but those without it can download it here: Download Microsoft SQL Server Compact 3.5 Service Pack 2 for Windows Desktop from Official Microsoft Download Center
Begin by downloading the ISXtoBSDF converter zip file from the Downloads section above. Extract the folder into your folder of choice (this folder choice is not important for the operation of the converter).
Within the extracted folder, there are two files, the ISXtoBSDF.msi, and setup.exe. Run either file to open the IsxToBSDF Setup Wizard.
Select ‘Next’ to arrive at the ‘Select Installation Folder’ page, where the installation location can be changed to the user’s preference. By default, the converter will install in the Program Files, but it may be preferable to install somewhere else. Take note that to use the converter, all the ISX files to be converted must be located inside the same folder as the converter .exe file, and the converted .BSDF files will be generated in this same folder as well.
Figure 1: Default Installation location (left), example arbitrary folder (named ‘ISXtoBSDF’) in the user’s Documents folder (right)
Continue through the setup wizard until the installation of the converter is complete.
Navigate to the converter’s location through the file explorer to find the ‘ISXtoBSDF.exe’ converter, as well as the .dll files that are required for the converter to run. Do not delete or remove these .dll files from the folder that houses the ISXtoBSDF.exe file.
With installation complete, the converter is ready for use.
Operation
There are 2 simple methods for using the ISX-to-BSDF converter tool: the Drag-and-Drop method, and the Command Line method. Either process will generate a .BSDF file for each surface (front and/or back) and scatter type (reflection and/or transmission) measurement included in the .ISX file.
To function properly, be sure to move any to-be-converted .ISX files into the same folder as the converter executable file. As an example, this article will convert the .ISX files, ‘Actar_Fractal_Black_1776_S-04.isx’ and ‘BrightView_CHH55.isx’, and they are located in the same folder as ‘ISXtoBSDF.exe’, as shown in the image of the example folder below.
Method 1: Drag-and-Drop
In the first method, the user can simply select a single .ISX file, or multiple .ISX files, and drag them onto the ISXtoBSDF.exe file in the file explorer window.
After dropping the files onto the executable, a command window should appear that will display the status of the conversion and any errors that may occur. The error messages and their meanings are shared at the end of this article.
Once the conversion of the files is complete, the new .bsdf files should be present in the converter folder and are ready for use in OpticStudio.
Method 2: Command Line
Alternatively, a user can run the ISX-to-BSDF converter from the Windows Command Prompt window.
Open the Command Prompt window and navigate the system into the folder that holds the converter executable by typing the ‘cd’ command and then pasting the folder’s directory path. After pressing enter, the command line should now show that the system is focusing inside of the desired folder.
Then, to run the converter with a certain ISX file, simply type in the name of the converter, ‘ISXtoBSDF.exe’, followed by a space, and then the name, or names, of the ISX file(s). If multiple .ISX files are used, include a space between the file names. In this example, the command line prompt is ‘ISXtoBSDF.exe Acktar_Fractal_Black_1776_S-04.isx BrightView_CHH55.isx’, as shown in the example image below.
After pressing Enter, the same status messages appear in the Command Prompt window as appeared for the Drag-and-Drop method, then the conversion is complete and the Command Line is ready for use again.
Importing BSDF data
After the conversion of the files are complete, the .BSDF files need to be placed in a folder accessible to OpticStudio. By default, the Zemax folder is located in the user’s Documents folder. Copy or move the new .BSDF files into the Zemax…ScatterData folder, and they will then be accessible through OpticStudio.
Error Messages
The ISX-to-BSDF converter is equipped with a few Error Messages that will alert the user when a problem has occurred. These error messages are included here with the reason for the thrown error. These are generated when using the Command Line method of using the computer, and the converter will give these messages before moving on to the next line of commands.
| Error Message | Explanation |
| “No args, Display help. file1.isx file2.isx…. Specifies the .isx file(s) to convert to .bsdf scatter files.” | There is no filename input. |
| “Error: xxx is not an ISX file. Skipping this file.” | The input filename has an incorrect extension. |
|
The input .ISX file name is not in the right format, (e.g. it includes quotation marks, or a space)
| |
| “Error: ISX file xxx.isx does not exist. Skipping this file.” | The input .ISX file name does not exist. |
| “Error: xxx.ISX file is incomplete, please check converted .BSDF file!” | The input .ISX file does not contain the expected data (e.g. when the converter asks for a bsdf value at a certain angle/wavelength data point, but the library reports an error) The converter will give this error and fill in ‘0’ for the bsdf values of concern, then continue to process the file. |
| “Error: insufficient memory!” | This error is thrown when there are large arrays of data that need to be stored, but the user’s computer does not have enough free memory. The converter will terminate and show this error message. |
| - | Missing Data Condition is detected – an error message specific to the missing data will notify the user and give the user the option to halt the conversion or allow the system to replace the missing data with the closest available equivalent. |
Conclusion
With the end of support for the .ISX file format, the ISX-to-BSDF converter tool has been developed to allow OpticStudio users to create equivalent files in the familiar .BSDF format. Once the standalone converter file is installed, users may freely create .BSDF files at their leisure. No current OpticStudio needs to be running to make the conversion, and the .BSDF files are available for use and sharing as desired.