Combine all mesh of children into one mesh

MeshCombiner.cs

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(MeshFilter))]
[RequireComponent(typeof(MeshRenderer))]
public class MeshCombiner : MonoBehaviour {

    void Start() {
        MeshFilter[] meshFilters = GetComponentsInChildren<MeshFilter>() as MeshFilter[];
        
        CombineInstance[] combine = new CombineInstance[meshFilters.Length];
        for (int i = 0; i < meshFilters.Length; ++i) {
            combine[i].mesh = meshFilters[i].sharedMesh;
            combine[i].transform = meshFilters[i].transform.localToWorldMatrix;
            
            if( meshFilters[i].gameObject != gameObject ) {
              meshFilters[i].gameObject.SetActive(false);
            }
        }
		
		MeshFilter mf = GetComponent<MeshFilter>() as MeshFilter;

        mf.mesh = new Mesh();
        mf.mesh.CombineMeshes(combine);
        mf.mesh.Optimize();
        mf.mesh.RecalculateBounds();
    }
}