Example of free form deformation using Unity. Full package can be found in my main repository: https://github.com/Jerdak/FreeFormDeformation/tree/master/Unity

FreeFormDeformer.cs

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

/// <summary>
/// Helper class that represents a parameterized vertex
/// </summary>
public class Vector3Param {

  ///bernstein polynomial packing 
	public List<List<float>> bernPolyPack;

	///Point after applying s,t,u to p0, should result in original point
	public Vector3 p = Vector3.zero;

	///Origin
	public Vector3 p0 = Vector3.zero;

	///Distances along S/T/U axes
	public float s,t,u;

	public Vector3Param()
	{
		s = 0.0f;
		t = 0.0f;
		u = 0.0f;
	}

	public Vector3Param(Vector3Param v)
	{
		s = v.s;
		t = v.t;
		u = v.u;
		p = v.p;
		p0 = v.p0;
	}

};

/// <summary>
/// Free form deformation class
/// 
/// Based off of the paper 'Free-Form Deformation of Solid Geometric Models'[1] this class
/// creates a system of control points that can deform a mesh as if that mesh was embedded
/// in a flexible parallelpiped.
/// 
/// Confused?  Yeah, who uses the term parallelpiped.  The idea is to create a uniformly spaced
/// grid of control points around some mesh.  Each control point has some effect on the mesh, like
/// bone weighting in animation.  The effect each control point has is directly proportional to the
/// total number of control points in the entire grid, each exerts some control.
/// 
/// [1] - http://pages.cpsc.ucalgary.ca/~blob/papers/others/ffd.pdf
/// </summary>
public class FreeFormDeformer : MonoBehaviour {

	/// <summary>
	/// Allow FixedUpdate to modify the mesh.
	/// </summary>
	public bool AllowMeshUpdate = false;

	/// <summary>
	/// Animate control points
	/// </summary>
	public bool AnimateControlPoints = false;

	/// <summary>
	/// Target to be morphed
	/// </summary>
	Mesh MorphTarget = null;

	/// <summary>
	/// Target to be filtered (assumed to contain a meshfilter and valid mesh)
	/// </summary>
	public MeshFilter MorphTargetFilter = null;

	/// <summary>
	/// Update frequency in seconds
	/// </summary>
	public float UpdateFrequency = 1.0f;

	/// <summary>
	/// Game object to represent a control point.  Can be anything really, I suggest spheres.
	/// </summary>
	public GameObject ControlPointPrefab;

	/// <summary>
	/// Local coordinate system
	/// </summary>
	Vector3 S, T, U;

	/// <summary>
	/// Number of controls for S, T, & U respectively.  (L,M, and N MUST be >= 1)
	/// </summary>
	public int L=1, M=1, N=1;

	/// <summary>
	/// Time elapsed since last update
	/// </summary>
	float elapsedTime = 0.0f;
	float elapsedAnimationTime = 0.0f;
	int animationDirection = 1;

	/// <summary>
	/// Grid of controls points. Stored as 3D grid for easier because width,height, and depth can randomly vary. 
	/// </summary>
	GameObject[, ,] controlPoints;

	/// <summary>
	/// Original vertices from MorphTarget
	/// </summary>
	Vector3[] originalVertices;

	/// <summary>
	/// Current updated vertices for MorphTarget
	/// </summary>
	Vector3[] transformedVertices;


	/// <summary>
	/// Vertex parameters
	/// 
	/// Each vertex is given a set of parameters that will define
	/// its final position based on a local coordinate system.
	/// </summary>
	List<Vector3Param> vertexParams = new List<Vector3Param>();

	void Start () {
		MorphTarget = MorphTargetFilter.mesh ;
		originalVertices = MorphTarget.vertices;
		transformedVertices = new Vector3[originalVertices.Length];

		Parameterize();
	}

	/// <summary>
	/// Calculate a binomial coefficient using the multiplicative formula
	/// </summary>
	float binomialCoeff(int n, int k){
		float total = 1.0f;
		for(int i = 1; i <= k; i++){
			total *= (n - (k - i)) / (float)i;
		}
		return total;
	}

	/// <summary>
	/// Calculate a bernstein polynomial
	/// </summary>
	float bernsteinPoly(int n, int v, float x)
	{
		return binomialCoeff(n,v) * Mathf.Pow(x, (float)v) * Mathf.Pow((float)(1.0f - x), (float)(n - v));
	}

	/// <summary>
	/// Calculate local coordinates
	/// </summary>
	void calculateSTU(Vector3 max, Vector3 min){
		S = new Vector3(max.x - min.x, 0.0f, 0.0f);
		T = new Vector3(0.0f, max.y - min.y, 0.0f);
		U = new Vector3(0.0f, 0.0f, max.z - min.z);
	}

	/// <summary>
	/// Calculate the trivariate bernstein polynomial as described by [1]
	/// 
	/// My method adapts [1] slightly by precalculating the BP coefficients and storing
	/// them in Vector3Param.  When it comes time to extract a world coordinate, 
	/// it's just a matter of summing up multiplications through each polynomial from eq (2).
	/// </summary>
	/// <links>
	///  [1] - Method based on: http://pages.cpsc.ucalgary.ca/~blob/papers/others/ffd.pdf
	/// </links>
	/// <param name="p0">Origin of our coordinate system (where STU meet)</param>
	void calculateTrivariateBernsteinPolynomial(Vector3 p0){
		Vector3 TcU = Vector3.Cross(T, U);
		Vector3 ScU = Vector3.Cross(S, U);
		Vector3 ScT = Vector3.Cross(S, T);

		float TcUdS = Vector3.Dot(TcU, S);
		float ScUdT = Vector3.Dot(ScU, T);
		float ScTdU = Vector3.Dot(ScT, U);

		for (int v = 0; v < originalVertices.Length; v++)
		{
			Vector3 diff = originalVertices[v] - p0;

			Vector3Param tmp = new Vector3Param();
			tmp.s = Vector3.Dot(TcU, diff / TcUdS);
			tmp.t = Vector3.Dot(ScU, diff / ScUdT);
			tmp.u = Vector3.Dot(ScT, diff / ScTdU);
			tmp.p = p0 + (tmp.s * S) + (tmp.t * T) + (tmp.u * U);
			tmp.p0 = p0;
			tmp.bernPolyPack = new List<List<float>>();

			{	// Reserve room for each bernstein polynomial pack.
				tmp.bernPolyPack.Add(new List<float>(L));	//outer bernstein poly
				tmp.bernPolyPack.Add(new List<float>(M));	//middle bernstein poly
				tmp.bernPolyPack.Add(new List<float>(N));	//inner bernstein poly
			}

			{	// Pre-calculate bernstein polynomial expansion.  It only needs to be done once per parameterization
				for (int i = 0; i <= L; i++)
				{
					for (int j = 0; j <= M; j++)
					{
						for (int k = 0; k <= N; k++)
						{
							tmp.bernPolyPack[2].Add(bernsteinPoly(N, k, tmp.u));
						}
						tmp.bernPolyPack[1].Add(bernsteinPoly(M, j, tmp.t));
					}
					tmp.bernPolyPack[0].Add(bernsteinPoly(L, i, tmp.s));
				}
			}
			vertexParams.Add(tmp);
			if (Vector3.Distance(tmp.p, originalVertices[v]) > 0.001f)
			{
				//Debug.Log("Warning, mismatched parameterization");
			}
		}
	}

	/// <summary>
	/// Parameterize MorphTarget's vertices
	/// </summary>
	void Parameterize(){
		Vector3 min = new Vector3(Mathf.Infinity,Mathf.Infinity,Mathf.Infinity);
		Vector3 max = new Vector3(-Mathf.Infinity,-Mathf.Infinity,-Mathf.Infinity);
		foreach(Vector3 v in originalVertices){
			max = Vector3.Max(v,max);
			min = Vector3.Min(v,min);
		}
		calculateSTU(max, min);
		calculateTrivariateBernsteinPolynomial(min);
		createControlPoints(min);
	}


	/// <summary>
	/// Create grid of control points.
	/// </summary>
	void createControlPoints(Vector3 origin){
		controlPoints = new GameObject[L + 1, M + 1, N + 1];
		for(int i = 0; i <= L; i++){
			for(int j = 0; j <= M; j++){
				for(int k = 0; k <= N; k++){
					controlPoints[i, j, k] = createControlPoint(origin, i, j, k);
				}
			}
		}
	}

	/// <summary>
	/// Create a single control point.
	/// </summary>
	GameObject createControlPoint(Vector3 p0, int i, int j, int k)
	{
		Vector3 position = p0 + (i / (float)L * S) + (j / (float)M * T) + (k / (float)N * U);
		GameObject go = (GameObject)Instantiate(ControlPointPrefab, position, Quaternion.identity);
		go.transform.parent = transform;
		return go;
	}

	/// <summary>
	/// Convert parameterized vertex in to a world coordinate
	/// </summary>
	Vector3 getWorldVector3(Vector3Param r){
		int l = L;
		int m = M;
		int n = N;

		Vector3 tS = Vector3.zero;
		for(int i = 0; i <= l; i++){
			
			Vector3 tM = Vector3.zero;
			for(int j = 0; j <= m; j++){

				Vector3 tK = Vector3.zero;
				for(int k = 0; k <= n; k++){
					tK += r.bernPolyPack[2][k] * controlPoints[i,j,k].transform.localPosition;
				}
				tM += r.bernPolyPack[1][j] * tK;
			}
			tS += r.bernPolyPack[0][i] * tM;
		}
		return tS;
	}


	void UpdateMesh(){
		elapsedTime = 0.0f;

		int idx = 0;
		foreach(Vector3Param vp in vertexParams){
			Vector3 p = getWorldVector3(vp);
			transformedVertices[idx++] = p;
		}

		MorphTarget.vertices = transformedVertices;
		MorphTarget.RecalculateBounds();
		MorphTarget.RecalculateNormals();
		MorphTarget.Optimize();
	}

	void OnGUI(){
		AllowMeshUpdate = GUI.Toggle(new Rect(5, 5, 150, 25), AllowMeshUpdate, "Allow Mesh Updates");
		GUI.TextArea(new Rect(25, 25, 225, 225), "Controls\n--------\n- Left Click + Mouse Move: Rotate\n- Left Click on Points: Select Point\n- WASD: Translate X/Y\n- ZX: Zoom In/Out");
	}
	void FixedUpdate()
	{
		elapsedTime += Time.fixedDeltaTime;
		if (AllowMeshUpdate)
		{
			if (elapsedTime >= UpdateFrequency) UpdateMesh();
		}
	}
	void Animate(){
	//	elapsedTime += (Time.fixedDeltaTime * animationDirection);
	//	if (elapsedTime < 0.0f | elapsedTime > 4.0f) animationDirection = -animationDirection;

		//foreach(GameObject go in controlPoints){
		//	Vector3 dir = 
	//	}

	}
	// Update is called once per frame
	void Update () {
		if(AnimateControlPoints)Animate();
	}
}

@lixiangflyin Sorry for the late response. Github doesn't seem to provide a notification mechanism for comments on gists. Yes you certainly could realize FFD on an iOS device but you'll need to keep your poly count low or rewrite my code to be less intensive (don't update all vertices each frame, only when a control point has finished moving.)

Hello I was wondering can you give me any directions how to set up the unity application to try out the deformer? I have tried few things with the control shapes and tried to use cube on which to change the shape , but i am missing something.