Add shell fracture function

[keqingsdog]

If the algorithm itself supports this, can cloth fracture be added in the future?

Since real-time solving during runtime is not supported, here are several control solutions:

1. Pre-make vertex groups, then separate the vertices inside the vertex group at specified keyframes.
2. Or perform mesh tearing based on a set stretch tearing threshold.
3. Colliders trigger surface cutting; add a toggle attribute to static objects, which allows creating animations of blades cutting cloth.

[ryichando]

Hi! Yes that idea is something I tried, but topology changes seem the most technically challenging aspect.

Just in case you haven’t seen this, mesh tearing is discussed here: #58

This is internally already tested and works, but delivering it to Blender seems to require hefty engineering effort. I attempted to use coding agents for this, but they have all failed as of today.

If you have good ideas, please continue the discussion there.

[ryichando]

Let me share something that seems to work now: using the Weld modifier, we can do this.

After the simulation finishes, we know all the topologically separated islands. Then we destructively tear the initial mesh, though not as an actual runtime tear. Visually, they still look connected through the Weld modifier. As tearing happens, we simply separate these islands, and the tear appears naturally.

The issue is that in realtime preview, things look weird when tearing happens because we can’t change the topology during live fetch. We could reconstruct the topology every time, but that is too expensive.