リアルタイムに布シミュレーションをしながらメッシュを動的に変化させるスクリプト

DynamicCreateMesh.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

[RequireComponent(typeof(SkinnedMeshRenderer))]
[RequireComponent(typeof(Cloth))]
public class DynamicCreateMesh : MonoBehaviour
{
	[SerializeField]
	private Material _mat;

	private SkinnedMeshRenderer meshRenderer;

	public List<Vector3> vertices;
	List<Square> squares;

	[SerializeField]
	private float size = 1f;

	[SerializeField]
	private int height = 20;
	[SerializeField]
	private int width = 10;

	// 四角形の情報
	public class Square
	{
		public int h, w;
		public List<int> triangles;

		public Square (int _h, int _w, List<int> _triangles)
		{
			h = _h;
			w = _w;
			triangles = _triangles;
		}
	}
	private Square GetSquare (int _h, int _w)
	{
		foreach (Square st in squares) {
			if (st.h == _h && st.w == _w) {
				return st;
			}
		} 
		return null;
	}

	private void Start ()
	{
		//メッシュをセットするよ
		meshRenderer = GetComponent<SkinnedMeshRenderer> ();

		// メッシュ情報を扱いやすいように保持しておくよ
		squares = new List<Square> ();
		vertices = new List<Vector3> ();

		for (int h = 0; h < height; ++h) {
			for (int w = 0; w < width; ++w) {

				vertices.Add (new Vector3 ((1f + w) * size, 0, (1f + h) * size));
				vertices.Add (new Vector3 ((1f + w) * size, 0, (0f + h) * size));
				vertices.Add (new Vector3 ((0f + w) * size, 0, (0f + h) * size));
				vertices.Add (new Vector3 ((0f + w) * size, 0, (1f + h) * size));

				List<int> triangles = new List<int> ();

				triangles.Add (0 + (w + (h * width)) * 4);
				triangles.Add (1 + (w + (h * width)) * 4);
				triangles.Add (2 + (w + (h * width)) * 4);
				triangles.Add (0 + (w + (h * width)) * 4);
				triangles.Add (2 + (w + (h * width)) * 4);
				triangles.Add (3 + (w + (h * width)) * 4);

				// 反対側からの描画にも対応
				triangles = DuplicateReverseTriangles (triangles);

				squares.Add (new Square (h, w, triangles));
			}
		}

		UpdateMesh (true);
	}

	private void UpdateMesh (bool isInit = false)
	{
		var mesh = isInit ? new Mesh () : meshRenderer.sharedMesh;

		List<int> allTriangles = new List<int> ();

		foreach (Square st in squares) {
			allTriangles.AddRange (st.triangles);
		} 
		mesh.Clear ();
		mesh.vertices = vertices.ToArray ();
		mesh.triangles = allTriangles.ToArray ();
		meshRenderer.sharedMesh = mesh;
	}

	private List<int> DuplicateReverseTriangles (List<int> triangles)
	{
		int setCount = triangles.Count / 3;
		for (int i = 0; i < setCount; ++i) {
			triangles.Add (triangles [0 + (i * 3)]);
			triangles.Add (triangles [2 + (i * 3)]);
			triangles.Add (triangles [1 + (i * 3)]);
		}
		return triangles;
	}

	// 指定した四角形を切断
	// 一旦テスト用に単純な分割のみに対応
	public void Cut (int h, int w)
	{
		Square square = GetSquare (h, w);

		int maxIndex = vertices.Count;

		float bottomRate = 0.8f;
		float topRate = 0.8f;
		float interval = 0.05f;

		vertices.Add (new Vector3 ((bottomRate + interval + w) * size, 0, (0f + h) * size));
		vertices.Add (new Vector3 ((topRate + interval + w) * size, 0, (1f + h) * size));
		vertices.Add (new Vector3 ((topRate - interval + w) * size, 0, (1f + h) * size));
		vertices.Add (new Vector3 ((bottomRate - interval + w) * size, 0, (0f + h) * size));

		List<int> triangles = new List<int> ();

		triangles.Add (0 + (w + (h * width)) * 4);
		triangles.Add (1 + (w + (h * width)) * 4);
		triangles.Add (0 + maxIndex);

		triangles.Add (0 + (w + (h * width)) * 4);
		triangles.Add (0 + maxIndex);
		triangles.Add (1 + maxIndex);

		triangles.Add (2 + maxIndex);
		triangles.Add (3 + maxIndex);
		triangles.Add (2 + (w + (h * width)) * 4);

		triangles.Add (2 + maxIndex);
		triangles.Add (2 + (w + (h * width)) * 4);
		triangles.Add (3 + (w + (h * width)) * 4);

		triangles = DuplicateReverseTriangles (triangles);

		square.triangles = triangles;

		maxIndex += 4;

		UpdateMesh ();
	}

	public void Execute()
	{
		for (int h = 0; h < height; ++h) {
			Cut (h, width / 2);
		}
	}

	void Update ()
	{
		// スペースキーで切断実行
		if (Input.GetKeyDown (KeyCode.Space)) {
			Execute ();
		}
	}
}

この記事で説明?してあります。
http://kohki.hatenablog.jp/entry/UnityDynamicCutClothImpossible