Unity Mesh Combiner

An editor tool for Unity that merges multiple meshes into a single combined GameObject while preserving all original materials. It drastically reduces draw calls (batches), supports an unlimited number of vertices, and is fully undo‑able.

Overview

When a scene contains many small objects with MeshRenderers, each one generates at least one draw call – quickly bottlenecking the CPU, especially on mobile or VR platforms.
Unity Mesh Combiner merges all meshes from the selected hierarchy into one new GameObject, keeping all materials as separate submeshes. The result: hundreds of draw calls become just a few, dramatically improving rendering performance.

Even if your objects use different materials, the tool creates a single combined mesh that contains all materials in the correct order. No material is lost – every original material is present in the final result.

Features

• One mesh, all materials – all objects are combined into a single GameObject with a multi‑material mesh. Each unique material gets its own submesh, preserving the exact look.
• Massive draw call reduction – same‑material geometry ends up in the same submesh, minimizing the total number of draw calls.
• Works in all Unity versions – tested from older releases up to the latest (including Unity 6.3).
• 32‑bit index support – handles meshes with millions of vertices, no 65k vertex limit.
• World‑space transformation – every object's position, rotation, and scale is correctly applied.
• Original objects are disabled (not deleted) – you can easily inspect or re‑enable them later.
• Full Undo / Redo – every step (creation, disabling) is registered with Unity’s Undo system.
• Clear logging – the Console reports exactly how many meshes were combined and how many materials were kept.

How It Works

1. Collect all MeshFilters from the selected GameObjects and their children (only active objects).
2. Group submeshes by material – each submesh of every mesh is assigned to the list of the material it uses.
3. Create temporary meshes per material – all geometry that shares the same material is merged into one intermediate mesh (vertices already in world space).
4. Combine into one final mesh – these intermediate meshes become separate submeshes of the final mesh, preserving the material order.
5. Spawn a new GameObject with a MeshFilter and MeshRenderer, assign the combined mesh and the full materials array.
6. Disable the original objects so they are no longer rendered.
7. Select the new object in the Hierarchy for immediate feedback.

Because the tool groups geometry by material before the final combine, the resulting GameObject contains exactly one submesh per unique material – guaranteeing the smallest possible number of draw calls for your scene setup.

Installation & Usage

1. Copy the UnityMeshCombiner.cs script into an Editor folder (e.g., Assets/Editor/).
   The [MenuItem] attribute requires the script to be inside an Editor folder, otherwise it won’t compile or appear.
2. Wait for Unity to compile.
3. In the Hierarchy, select one or more root GameObjects.
   The tool will also process all children of the selected objects.
4. From Unity’s top menu, choose Tools → Combine Meshes.
5. A new GameObject named CombinedMesh appears in the scene.
   • All original materials are preserved on the new object.
   • The original objects become inactive but remain in the hierarchy.

Performance Benefits

• Draw calls / Batches: The primary goal. A scene with 500 identical rocks and 10 materials can go from 500 draw calls down to just 10.
• SetPass calls: Reduced proportionally because materials are shared.
• No Static flag required – works at edit time and creates a real mesh asset you can further edit or export.
• Mobile / VR friendly – huge CPU overhead reduction, directly improving frame rate on devices limited by draw‑call throughput.

Important Limitations

• Colliders are not preserved – the new combined GameObject does not have any Collider components. The original objects (and their colliders) are disabled. If you need physics, you can:
  • Add a MeshCollider to the combined object (using the combined mesh).
  • Manually place colliders on the new object.

Compatibility

Works in all modern Unity versions – from the older releases up to the very latest.
Tested specifically in Unity 6.3, but the tool relies only on basic mesh APIs that have been stable for years, so it should work without issues in any version you are using.

License

MIT – free to use, modify, and distribute in any project.

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Happy combining! 🚀