Create mesh sample

mesh.cs

    private void CreateMesh()
    {
        var start = Quaternion.AngleAxis(-45, Vector3.up) * Vector3.forward * 6f;
        var end = Quaternion.AngleAxis(45, Vector3.up) * Vector3.forward * 6f;
        var control = Vector3.forward * 6f;

        var points1 = GetPointsInCurve(start, end, control, 20);

        start = Quaternion.AngleAxis(15, Vector3.right) * start;
        end = Quaternion.AngleAxis(15, Vector3.right) * end;
        control = Quaternion.AngleAxis(15, Vector3.right) * control;

        var points2 = GetPointsInCurve(start, end, control, 20);

        var verts = new Vector3[40];
        Array.Copy(points1, 0, verts, 0, 20);
        Array.Copy(points2, 0, verts, 20, 20);

        int[] indices = new int[6 * 20];
        for (int i = 0; i < 20 - 1; i++)
        {
            var p1 = i;
            var p2 = i + 1;
            var p3 = 20 + i;
            var p4 = 20 + i + 1;

            indices[6 * i] = p1;
            indices[6 * i + 1] = p2;
            indices[6 * i + 2] = p3;
            indices[6 * i + 3] = p3;
            indices[6 * i + 4] = p2;
            indices[6 * i + 5] = p4;
        }

        var mesh = new Mesh();
        mesh.vertices = verts;
        mesh.triangles = indices;
        mesh.RecalculateBounds();
        mesh.RecalculateNormals();
        mesh.Optimize();

        gameObject.GetComponent<MeshFilter>().mesh = mesh;
    }

    private Vector3[] GetPointsInCurve(Vector3 start, Vector3 end, Vector3 control, int count)
    {
        var points = new Vector3[count];

        for (var i = 0; i < count; i++)
        {
            var t = (float)i / (float)(count - 1);
            var p = start * (1f - t) * (1f - t) + control * 2f * (1f - t) * t + end * t * t;

            points[i] = p;
        }

        return points;
    }