One Shot Prompt — World Generation in Unity

A single prompt that drives an AI coding agent to generate a complete procedural 3D landscape inside the Unity Editor — by driving the editor directly through Unity MCP, or by writing C# scripts the user runs in the editor.

What it generates

A realistic procedural landscape built in 6 layers:

1. Terrain mesh — FBM heightfield with momentum-based hydraulic erosion, two-phase hydrology (rivers + lakes), and seed-driven feature probability (ocean edges, lakes, 1–5 rivers)
2. Terrain textures — unified 4K context-aware bake with heightlerp blending (flow accumulation and carve depth as regular splatting inputs, wetness as continuous post-blend modifier)
3. River water — mask-based transparent water mesh following every carved channel
4. Pine forest — Poisson-disk clumped trees with power-law scale and slope orientation
5. Lighting & post-processing — sun, shadows, ambient, ACES tonemapping, bloom, color grading
6. Sky & clouds — procedural sphere-cluster clouds at altitude

Requirements

• Unity 2022.3+ with URP (Universal Render Pipeline)
• An AI coding agent (Claude Code, Cursor, Windsurf, Copilot, etc.)
• Unity MCP server (recommended) — setup guide

How agents work

There are two valid execution paths:

Path A — Unity MCP (recommended)

The agent executes C# code directly in the Unity Editor through Unity MCP's execute_code tool. No script files are written — code runs immediately at runtime like an editor console. This is the fastest feedback loop and the preferred path.

Setup: Follow the Unity MCP setup guide to install and connect the server, then use an agent that supports MCP tool calling.

Path B — C# scripts (no MCP required)

The agent writes .cs Editor scripts into your Assets folder. Each script uses [MenuItem] or runs as an Editor utility that you trigger manually from the Unity menu. The agent tells you which script to run and in what order.

Setup: No extra tools needed — just Unity and an AI coding agent.

How to run

Step 1 — Set up Unity

• Create a Unity 2022.3+ project with URP (Universal Render Pipeline) configured
• (Optional) Install Unity MCP for Path A

Step 2 — Start the prompt

Option A — with repo cloned: Clone this repo into Assets/ and point your agent at WORLD-GENERATION-PROMPT.md.

Option B — no repo: Copy the entire contents of WORLD-GENERATION-PROMPT.md and paste it to your agent as the first message.

WORLD-GENERATION-PROMPT.md contains everything: global rules, run ID setup, and all 6 layer prompts in order. The agent runs all layers autonomously.

Run isolation

Each run is self-contained so you can compare results from multiple agents without contamination.

The agent auto-generates a run ID from its model name and today's date — e.g. claude-opus-4-6-2026-04-10/, gpt-5-2026-04-10/. You can also specify a custom run ID in the prompt.

All assets and the scene for a run live under:

Assets/WorldGenRuns/{run-id}/

To review a run later, open Assets/WorldGenRuns/{run-id}/run-scene.unity. Previous runs are untouched.

Key rules

• Run isolation: All assets saved under Assets/WorldGenRuns/{run-id}/. Never write to shared folders.
• Fresh generation: Every texture, material, and mesh must be generated from scratch by the agent. No reusing existing asset files.
• Scale (1,1,1): All objects use transform.localScale = (1,1,1). Map size is controlled by mesh geometry, not transform scale.
• Layer isolation: Each layer only adds — never modifies previous layers' terrain, textures, or water.
• Raycast grounding: All props are placed via downward raycast to ProceduralMeshGround.

Community

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