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Before starting this tutorial, read Working with Data to understand Groups, Resource Types, and Prototypes.
This guide walks you through setting up a basic vegetation spawn using the Terrain Spawner tool and the Unity/GameObject resource type. By the end you will have a working spawner that places trees across your terrain with a single click.

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Before you begin

You need:
  • A Unity project with MegaWorld installed.
  • A terrain in your scene.

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Step 1 — Create a Terrain Spawner

Go to GameObject > MegaWorld > Add Terrain Spawner. A new Terrain Spawner object appears in your Hierarchy. Its Transform scale defaults to (500, 500, 500), which sets the initial stamper area size. You can create several Terrain Spawners and switch between them — each one holds its own group stack and settings.

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Step 2 — Add a Group

Select the Terrain Spawner in the Hierarchy. In the MegaWorld Window, click Add Type to create a new Group. A Group asset is created in your project. Rename it to something descriptive, for example Trees.

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Step 3 — Add prototypes to the Group

Inside the Group, click Add Resource and choose the resource type you want to spawn:
  • Unity/GameObject — standard Prefab instances placed in the scene.
  • Terrain Object — GPU-instanced objects managed by Renderer Stack.
  • Unity/Terrain Detail — grass and mesh detail painted onto Unity Terrain.
For a basic tree spawn, choose Unity/GameObject and drag your tree Prefabs into the prototype list.
You can add multiple Prefabs to the same Group. Terrain Spawner selects among them randomly during spawning, weighted by each prototype’s Success Settings, which helps break up visual repetition.

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Step 4 — Configure Scatter Settings

In the Group settings, expand Scatter Settings to control how sample positions are generated across the area. Increase density to spawn more objects per unit area, or switch the scatter mode to adjust the distribution pattern.

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Step 5 — Configure filters (optional)

Expand the Filter Settings for the Group. Add Mask Filters to restrict placement by height, slope, or terrain texture. Common setups:
  • Slope filter — trees on flat ground, rocks on steep slopes.
  • Height filter — snow only at high elevations.
  • Noise filter — organic cluster patterns.
On non-Unity-Terrain surfaces (polygon meshes), switch to Simple Filter, which evaluates height, slope, and noise directly from raycasts without requiring terrain data.

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Step 6 — Configure Transform Components (optional)

In the prototype settings, add Transform Components to randomize scale, rotation, or position offset for each placed object. At minimum, add a rotation randomizer so trees face different directions.

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Step 7 — Set the area and spawn

The stamper area is controlled by the Transform scale of the Terrain Spawner GameObject. Scale it in the Scene View to cover the terrain region you want to fill. In the Stamper Tool Controller section, click Spawn. Terrain Spawner evaluates each active Group and places objects across the area according to your scatter, filter, and transform settings.

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Step 8 — Enable Auto Respawn for fast iteration (optional)

Turn on Auto Respawn in the Stamper Tool Controller. With this on, Terrain Spawner automatically removes the current spawn result and re-runs the pass whenever you change a setting. Use Delay Auto Spawn to set a short wait in seconds before the respawn triggers. This is especially useful when tuning Mask Filters — you can adjust a slope or height filter and immediately see the result update in the scene without clicking Spawn manually.

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Adding Terrain Detail (grass)

To spawn grass or mesh details on Unity Terrain, add a second Group to the same Terrain Spawner (or create a separate one):
  1. Click Add Type and create a Group.
  2. Click Add Resource and choose Unity/Terrain Detail.
  3. Assign a detail prototype that matches one already registered in the Unity Terrain Inspector.
  4. In the prototype settings, configure Spawn Detail Settings:
    • Density — maximum detail count per terrain cell.
    • Use Random Opacity — adds variation so cells at the same filter fitness get different counts.
    • Failure Rate — randomly zeroes out some cells to create sparse gaps.
  5. Add Mask Filters to the prototype to control where the detail appears.
  6. Click Spawn.

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What’s next

  • Add more Groups to mix vegetation types in the same spawner.
  • Use Texture Stamper to paint terrain textures before running a vegetation pass.
  • Switch to Advanced Brush to paint vegetation interactively using the same Group settings.
  • Use Brush Modify to art-direct already spawned objects.
  • Read the full Terrain Spawner reference for all settings and behaviors.