Todd

Updated : October 30, 2024 10:26

Created : June 17, 2019 21:32

SYMPTOMS

When exporting curves/polylines to the Wavefront .OBJ file format Modo exports “faces” rather than "lines". This can cause lines to import incorrectly when the file is opened in Modo or other software packages.

CAUSE

When Modo exports the Wavefront .OBJ file, it generates the line item with the "f" element designation f xx/1, where the “f” represents faces, instead of the line element “l” for lines. The numbers in the line item represent the vertices of the face, and dictate in a 3D space where that face/line is placed. When viewing the exported curves Wavefront .OBJ in a text editor, the following screenshot displays an example of the aforementioned values with the incorrect face element designation:

When importing the Wavefront .OBJ back into Modo or other 3D applications that support the .OBJ file format, corrupt polys/faces are displayed in place of the curves/polylines. This behavior is unexpected and breaks the workflow when only wanting to export polylines/curves, as shown in the next screenshot:

The bug attributed for the exporting issue has been written as: ID 377236 - Exporting Curves in Modo creates undesired mesh polys or is missing after importing, depending on the file type.

RESOLUTION

A quick solution is to edit the Wavefront .OBJ file in a text editor to remove and replace the face element designation to that of the line element designation for correct ingesting. To do this, please follow the steps below:

1. Export the curves/polylines from Modo and save it as a Waveform .OBJ file.
2. Back-up the newly created file by making a copy.
3. Open any text editor application and drag&drop the Waveform .OBJ file to read it.
4. Change any lines beginning with the "f" face element f xx/1 xx/1 to the "l" line element l xx/1 xx/1.
5. Save the file from the text editor and re-import it into Modo with default settings.

Example output:

FURTHER READING

• For additional reading on what an .OBJ file contains, please view the wiki page for Wavefront .OBJ files.
  
• More information regarding Importing and Exporting File Formats in the Modo documentation.

FURTHER HELP

If you are having further difficulties with exporting, please open a Support ticket and let us know the problem you are encountering and the troubleshooting steps you have taken so far.

For more information on how to open a Support ticket, please refer to our article: Q100064: How to raise a support ticket

Example file: 

Please download the attachment to review changes made in a curves mesh object file. You can open the .OBJ files in any text editor, such as Notepad on Windows, gedit in CentOS, or TextEdit on macOS.