UnityTerrainConvertor

Latest update: 29 April 2025

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Table of Contents

1. Project Architecture
2. One‑Click Mesh Combination
3. One‑Click Mesh Export → OBJ
4. One‑Click Waypoint Pair Export
5. Isaac Gym UnityTerrainModule
6. Coordinate Alignment FAQ

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Project Architecture

├── Assets
│   ├── Prefab                # ⚙️ Example scene
│   ├── Scenes                # 🎬 Unity scenes
│   ├── Scripts               # 📜 C# utilities
│   │   ├── MeshCombiner          # 1‑click mesh combination
│   │   ├── OBJExporter           # 1‑click OBJ export
│   │   ├── ExportObjectPosition  # 1‑click waypoint export
│   │   └── …
│   └── ExampleResources      # 🗺️  Sample data
│       ├── map_v1                # Example map
│       └── isaac_gym_files       # Example Isaac Gym terrains
└── …

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1. One‑Click Mesh Combination

No more exporting & re‑importing terrains!

1. Group assets
   Put everything you want to combine under a single parent GameObject (e.g. Map).

2. Run the tool
   Select that parent in the Hierarchy, then choose
   Tools → Combine Meshes from the menu.

3. Result
   A new child called CombinedMesh appears containing the merged geometry.

Before	After

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2. One‑Click Mesh Export to OBJ File

1. Select the CombinedMesh GameObject.
2. Click Tools → Export Selected to OBJ and choose Export in ROS coordinate so the mesh aligns with Isaac Gym.
3. Save the file (e.g. Assets/ExampleResources/map_v1/CombinedMesh.obj).

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3. One‑Click Waypoint Pair Export

1. Create waypoints
   Under an empty parent (e.g. waypoints) add children named whatever you like (waypoint1, …). Give each an icon so they’re easy to see.
2. Tag them
   Add a tag named way_point (exact spelling) and apply it to every waypoint object.
3. Export
   Select the waypoints parent and run Tools → Export Object Positions (defaults are fine). The file (e.g. point_set_1.txt) is written next to your OBJ.
4. Move files
   Copy the entire map_v1 folder into your Isaac Gym resources.

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4. IsaacGym UnityTerrainModule

4.1 Minimal Integration

Call the three API hooks in your Legged Gym environment:

// create_envs()
terrainModule.Init(config);
terrainModule.AddToSim(sim);

// reset_idx()
terrainModule.OnEnvResetIdx(envIds);

4.2 Configuration

Use the point_pair_files field to load the waypoint file exported above.

4.3 Resampling Targets

When resampling, pull goals from the terrain module so everything stays in sync.

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5. About Coordinate Alignment

5.1 Why align coordinates?

• Mesh export writes local vertex positions.
• Waypoint export writes world positions.
• Therefore the mesh’s local axes must match the Unity world axes.

5.2 How to verify alignment

1. Inspect the Transform of your mesh and its parents.
2. Ensure that every parent up to the Scene has Position = (0,0,0) and Rotation = (0,0,0).

If CombinedMesh is at the origin in world space, exported OBJ and waypoint files will line up perfectly.

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🚀 Ready to go

• Combine → Export → Tag → Export → Train ✨
• PRs and issues welcome!