Support for T3 Transitions or Polygon Intersection Resolution?

[PinkGenji]

Hi,

I’m currently working on a 2D simulation involving dynamic tissue rearrangement, and I’ve implemented T1 and T2 transitions using Tyssue’s built-in functions. However, I'm encountering situations where polygons (cells) occasionally intersect or overlap, likely due to numerical integration or topological rearrangements.

In many vertex models, these cases are typically resolved via a T3 transition (e.g., doi:10.1016/j.pbiomolbio.2013.09.003), which handles polygon intersections by modifying the topology to restore a valid mesh.

I’ve searched the documentation and codebase but couldn’t find an explicit implementation of a T3 transition. I just wanted to check:

1) Does Tyssue currently support any form of T3 transition, or automated resolution of polygon overlaps?

2) If not, would you recommend a strategy for manually detecting and resolving such events within the Tyssue framework?

Any guidance would be greatly appreciated — thank you for your work on this library!

Cheers.

[glyg]

Hi @PinkGenji Thank you for using tyssue!

Triangular faces can be automatically eliminated in a simulation

You can look at this function in the code:

tyssue/src/tyssue/behaviors/sheet/basic_events.py

Line 183 in 14e93f8

default_check_tri_face_spec = {"geom": SheetGeometry}

[PinkGenji]

Hi @glyg, thanks for the information.

After giving it a second thought, I believe I’m more interested in the collision module in Tyssue, since it handles 2D collision detection and resolution. However, I couldn’t find any demo illustrating how it should be used within Tyssue. Could you please point me to an example or resource showing how to couple collision handling with a viscous solver with Event Manager?

Cheers,

[glyg]

Unfortunately, the collision detection and resolution are not correctly implemented or tested.

As for type 3 transition, there is an option here to perform 3 sided faces removal when performing a type 1 transition.
Alternately, you can use the check_tri_faces event here

[glyg]

PS: They are not because I do not have any time to work on it right now, nor for the foreseeable future.

I'll soon launch a call for new maintainers :)