terrain

Unity Open MCP — Terrain Extension

Skill for AI agents authoring Unity Terrain (heightmaps, splatmaps, trees, neighbor stitching) in a project through the unity-open-mcp MCP server.

This domain is embedded in the bridge and opt-in. Its tools use the built-in engine modules (UnityEngine.TerrainModule for Terrain / TerrainData, UnityEngine.CoreModule for TreePrototype / TerrainLayer) — no Unity package install is required, and they compile into every bridge build. Its tool group is hidden from ListTools until the connected session activates it.

Preconditions

• Unity Editor is open with the target project.
• unity_open_mcp_ping returns connected: true.
• The terrain tool group is activated — call unity_open_mcp_manage_tools(action="activate", group="terrain") before invoking any Terrain tool. Fresh sessions start with two default-on groups (core and gate-and-verify); activate the other groups you need on demand. Because these types are built-in, capabilities always reports the terrain group as available: true (no domainDefine).

Tool prefix

All five tools share the unity_open_mcp_terrain_ prefix and one tool group:

• unity_open_mcp_terrain_create — allocate TerrainData (+ optional .asset) and a Terrain GameObject.
• unity_open_mcp_terrain_set_heights — set a heightmap region from a 2D array of normalized 0-1 values.
• unity_open_mcp_terrain_paint_layer — paint one terrain layer's splat from a 2D alphamap; seeds a new TerrainLayer when the index is new.
• unity_open_mcp_terrain_place_trees — place tree instances (position + scale
  • rotation) against a prototype index; seeds a prototype from a prefab when the index is new.
• unity_open_mcp_terrain_set_neighbors — set the top / bottom / left / right neighbor Terrains for LOD stitching.

All five tools are mutating and accept the standard paths_hint; they run the full gate path. There are no read-only members in this group — read terrain state with unity_open_mcp_component_get / unity_open_mcp_object_get_data.