Unity Runtime Terrain

January 20, 2026 · View on GitHub

Edit Unity Terrains at runtime — height sculpting, texture painting, details, trees + simple undo/redo.

A lightweight runtime terrain editing system for Unity.
Attach RuntimeTerrain to a Terrain and modify it directly during play mode via a clean, scriptable API.

Ideal for terraforming, digging, explosions, editor-like sculpting, or gameplay-driven terrain deformation.

Terrain Gif

Demo: https://www.youtube.com/shorts/OJtpWjD3vbM

✨ Features

🏔️ Height Sculpting

RaiseRadial — smoothstep radial falloff brush
RaiseWithTexture — texture-based brush (red channel), optional rotation
Optional smoothing pass to reduce height stepping artifacts
Optional DelayLOD workflow for better performance
→ call FlushDelayedLOD() after finishing a stroke

🎨 Texture Painting (Alphamaps / Splatmaps)

PaintLayer — radial falloff, automatic layer re-normalization
PaintLayerWithTexture — texture-driven alpha painting with rotation

🌱 Details Painting (Grass / Detail Meshes)

PaintDetailsRadial — add or remove detail density with falloff

🌳 Trees

RemoveTreesRadial — removes all tree instances inside the brush radius
Tree placement helpers can be added later if needed

↩️ Undo / Redo (Snapshot-based)

SaveFullSnapshot — captures heights, alphamaps, details, and trees
LoadFullSnapshot — restores a previous terrain state

🧪 Sample Controller

SampleTerraformer demonstrates:

Mouse-driven terrain editing
Multiple modes (terraform, explosion, paint, details, trees)
One-step undo (Ctrl + Z)
VFX integration
Rigidbody wake-up after terrain changes

Use it as a reference or starting point, not a hard dependency.

⚠️ Notes & Limitations

Editing near terrain borders may cause visible seams (especially with neighboring terrains).
Border stitching is not handled yet.

🧱 Physics / Rigidbody Note

When modifying terrain heights at runtime, sleeping rigidbodies may not immediately react to collider changes.
This can result in objects appearing to float or stick.