How to Fix Runtime Terrain Painting Changes Not Persisting in Unity

Lost or shared terrain edits happen because TerrainData is a shared asset not your save data. Storing the deltas and reapplying them on load fixes it. Here is how.

How to fix it

1. Capture and serialize deltas

After runtime edits read back the changed height and alphamap regions with GetHeights/GetAlphamaps and store only the modified rectangles in your save file.

2. Reapply edits on load

On scene load, apply the saved deltas with SetHeights/SetAlphamaps to a fresh runtime copy so the world matches the player's prior changes.

3. Never mutate the source asset

Instantiate a runtime copy of TerrainData at startup and assign it to the terrain so edits do not leak into the project asset or across save slots.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.