# How do we want triple junctions to work?
**URL:** https://discourse.gplates.org/t/how-do-we-want-triple-junctions-to-work/3267
**Category:** Worldbuilding
**Created:** [21 July 2026 05:51 UTC](https://discourse.gplates.org/t/how-do-we-want-triple-junctions-to-work/3267 "2026-07-21T05:51:51Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@StephenRider](https://discourse.gplates.org/u/StephenRider)
#### Post date: [21 July 2026 05:51 UTC](https://discourse.gplates.org/t/how-do-we-want-triple-junctions-to-work/3267/1 "2026-07-21T05:51:51Z")
I’m using Codex to try to improve gPlates, so far I have one little bit that still needs work, the mythical split polygon with polyline:
>
>
> \## Summary
>
> \- add a World Building menu between Tools and Window, with a two-s…tage Split Plate command
> \- split a selected polygon with a selected polyline into two feature geometries while preserving original feature properties, untouched holes, reconstruction state, and undo support
> \- add the MinGW LONG\_BIT=32 compatibility definition needed by the Windows build toolchain
>
> \## Testing
>
> \- \[x\] Full gplates target build completed successfully after implementation
> \- \[x\] Final incremental compile of SplitPlateOperation.cc completed successfully
> \- \[\] Final executable relink was blocked because the running GPlates process currently holds gplates.exe open; no compiler errors were reported
the next thing I want to tackle is triple junctions, but how do we want these to work? Three topo lines that extend? Just the last excention since the last line was finished? Hid the old line and make one long new one?
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### Author:  [@crackdtoothgrin](https://discourse.gplates.org/u/crackdtoothgrin)
#### Post date: [23 July 2026 22:50 UTC](https://discourse.gplates.org/t/how-do-we-want-triple-junctions-to-work/3267/2 "2026-07-23T22:50:11Z")
I can think of different enough solutions to warrant more than one use case from my own workflow, if you find this helpful.
The easiest is to just extend an additional point to the center point of the triangle between the three. If there was a way to have multiple options for the end result I’d have it three (3) ways:
• Simple add point to end of existing line.
• Duplicate line to start at current timestamp and hide the former line at the same timestamp (or some arbitrary user-defined time like 0.1mya before).
• Make an entirely new MOR with two points that starts at the new timestep as an extension to the original, but entirely separate.
When I’m making triple junctions with an MOR I usually do the first one. Then, I can just cut and increment each addition/section using T and avoid weird overlaps by timing them to appear in stages.
I’d also think that there are use cases for the following:
• Extend all three lines such that the gap between them makes an equilateral triangle, then bank each endpoint to the adjacent MOR so that you could cut the sides of this new triangle in order to capture them in a temporary topology and use that to make a new plate between the MORs.
• Select two lines, and then have them meet at a right angle, then the third line connects to that, either directly or by reaching an arbitrary point such that the third line makes a right angle or similar RRF like structure.
I could probably go on, as my own kept list of suggestions to this software is quite long. If you need me to clarify, let me know!