public void ChangeTarget(int type)
    {
        for (int i = 0; i < num; i++)
        {
            var t = targets[i];

            if (type == 0)
            {
                t.x = (i % 8f - 3.5f) * 10f + 3.5f * (Random.value - 0.5f); // +
                t.z = Random.Range(-50f, 50f);
            }
            else if (type == 1)
            {
                t.x = Random.Range(-50f, 50f);
                t.z = Random.Range(-50f, 50f);
            }
            else
            {
                var pp = ImgPos.GetRandomPoint();
                t.x = -pp.x / 2f;
                t.z = -pp.y / 2f;

                if (Random.value < 0.3f)
                {
                    t.x = Random.Range(-50f, 50f);
                    t.z = Random.Range(-50f, 50f);
                }
            }



            targets[i] = t;
        }
    }
    private void Update()
    {
        //マウスが押されたら、適当にターゲット位置を入れ替える
        if (Input.GetMouseButtonDown(0))
        {
            var flag  = Random.value < 0.5f ? true : false;
            var flag2 = Random.value < 0.3f ? true : false;
            Debug.Log("mousedown");
            for (int i = 0; i < num; i++)
            {
                var t = targets[i];
                if (flag)
                {
                    t.x = (i % 8f - 3.5f) * 10f + 10.5f * (Random.value - 0.5f); //
                    t.z = Random.Range(-50f, 50f);
                }
                else
                {
                    //t.x = Random.Range(-50f, 50f);
                    //t.z = Random.Range(-50f, 50f);

                    //Debug.Log("au");
                    var pp = ImgPos.GetRandomPoint();
                    t.x = -pp.x / 2f;
                    t.z = -pp.y / 2f;

                    if (Random.value < 0.3f)
                    {
                        t.x = Random.Range(-50f, 50f);
                        t.z = Random.Range(-50f, 50f);
                    }
                }

                t.y = 0;//Random.Range(-0.1f, 0.1f);


                if (flag2)
                {
                    t.x = t.z = 0;
                }

                targets[i] = t;
            }
        }

        //足をじたばたする2コマぶんの計算
        var n = (Mathf.FloorToInt(Time.frameCount * 0.2f) % 2);

        for (int i = 0; i < num; i++)
        {
            //位置の更新
            var p = positions[i];

            var t = targets[i];
            var v = t - p;
            v = v / 20f;

            var lim = 0.1f + 0.05f * ((float)i / (float)num);
            if (v.magnitude > lim)
            {
                v = v.normalized * lim;
            }
            p           += v;
            positions[i] = p;

            //uniformを1個ずつ指定
            propertyBlock.SetFloat("_DT", i / 1000f);
            propertyBlock.SetColor("_Col", colors[i % colors.Count]);

            var q = Quaternion.Euler(
                new Vector3(
                    0,
                    (-Mathf.Atan2(v.z, v.x) + Mathf.PI / 2f) / Mathf.PI * 180f,
                    0
                    )
                );

            //描画
            Graphics.DrawMesh(m_mesh, p, q, m_mat, 0, null, 0, propertyBlock);


            //var mtx = new Matrix4x4();
            // var mtx = Matrix4x4.Translate(p);
            //mtx.tr
            //Graphics.DrawMeshInstanced(m_mesh,0,m_mat,mtx,propertyBlock,true,false);
        }
    }