対象の頂点INDEXが記録されたCSVを読み込んで，ノブを掴んで動かすと，対象の頂点が移動したり回転したりするスクリプト．

KnobScript.cs

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

public class KnobScript : MonoBehaviour
{

    public enum ControllType
    {
        TranslateY,
        TranslateX,
        TranslateZ,
        RotateX,
        RotateY,
        RotateZ,
    }

    public ControllType controllType;
    public GameObject targetObject;
    public TextAsset indexCsv;
    public bool inverse;

    Mesh mesh;
    Vector3[] vertices;
    List<int> targetIndices = new List<int>();

    Vector3 prevMousePos;
    bool clickFlag;

    // Use this for initialization
    void Start()
    {
        var lines = indexCsv.text.Split('\n');
        foreach (var line in lines)
        {
            if (line != "")		// 空文字列の排除
                targetIndices.Add(int.Parse(line));
        }

        mesh = targetObject.GetComponent<SkinnedMeshRenderer>().sharedMesh;
        prevMousePos = Input.mousePosition;
    }

    Vector3 CalculateCenter()
    {
        // 対象頂点の中心位置を求める
        Vector3 total = Vector3.zero;
        foreach (var ind in targetIndices)
        {
            total += vertices[ind];
        }
        float div = 1f / (float)targetIndices.Count;
        return total * div;
    }

    // 移動
    void Translate(Vector3 value)
    {
        foreach (var index in targetIndices)
        {
            vertices[index] = vertices[index] + value;
        }
    }

    // 回転
    void Rotate(Vector3 value)
    {
        var center = CalculateCenter();
        foreach (var index in targetIndices)
        {
            var vector = vertices[index] - center;	// 回転させるために一度ベクトルを作っておく
            var rotated = Quaternion.Euler(value) * vector;	// ベクトルの回転
            vertices[index] = rotated + center;		// 位置の調整
            Debug.Log(vertices[index]);
        }
    }


    void PinchKnob()
    {
        // マウスの差分を取って回転させる
        var difference = Input.mousePosition - prevMousePos;
        gameObject.transform.Rotate(new Vector3(0, -difference.x, 0));

        float i = inverse ? 1f : -1f;
        float t = i * difference.x * 0.001f;	// 移動の差分値
        float r = i * difference.x;

        switch (controllType)
        {
            case ControllType.TranslateY:
                Translate(new Vector3(0, t, 0));
                break;

            case ControllType.TranslateX:
                Translate(new Vector3(t, 0, 0));
                break;

            case ControllType.TranslateZ:
                Translate(new Vector3(0, 0, t));
                break;

            case ControllType.RotateX:
                Rotate(new Vector3(r, 0, 0));
                break;

            case ControllType.RotateY:
                Rotate(new Vector3(0, r, 0));
                break;

            case ControllType.RotateZ:
                Rotate(new Vector3(0, 0, r));
                break;
        }
        mesh.vertices = vertices;
    }

    // オブジェクトを掴んだかどうか判定する
    bool IsPinchObject()
    {
        var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        var hit = new RaycastHit();
        var hit_flag = Physics.Raycast(ray, out hit, 10);

        if (hit_flag && Input.GetMouseButton(0))
        {
            if (hit.transform == transform)
                return true;
        }
        return false;
    }

    // Update is called once per frame
    void Update()
    {
        vertices = mesh.vertices;

        if (IsPinchObject())
            PinchKnob();
        
        prevMousePos = Input.mousePosition;
    }
}