Unity 3D Procedural Terrain - Step 2 - Overapping Sine Wave

using UnityEngine;
using System.Collections;

public class TerrainStuff : MonoBehaviour {

    Terrain terrain;

    // Use this for initialization

    // frequencies
    float f1,f2;

    // heights
    float h1,h2;

    void OnGUI()
    {
        GUILayout.Label("Frequency 1: "+f1);
        f1 = GUILayout.HorizontalSlider(f1, .001f, 1f);

        GUILayout.Label("Height 1: "+h1);
        h1 = GUILayout.HorizontalSlider(h1, .01f, 1f);

        GUILayout.Label("Frequency 2: "+f2);
        f2 = GUILayout.HorizontalSlider(f2, .001f, 1f);

        GUILayout.Label("Height 2: "+h2);
        h2 = GUILayout.HorizontalSlider(h2, .01f, 1f);



    }


    void SetTerrainHeights () {

        terrain = GetComponent<Terrain>();

        TerrainData data = terrain.terrainData;

        float[,] heights = data.GetHeights(0, 0, data.heightmapWidth, data.heightmapHeight);

        for( int x=0; x<512; ++x)
        {
            for( int z=0; z<512; ++z)
            {
                // resuts
                float r1 =  Mathf.Sin ( x*f1 ) * h1 + h1;
                float r2 =  Mathf.Sin ( z*f2 ) * h2 + h2;

                heights[x,z] = r1 + r2;

            }
        }

        data.SetHeights(0, 0, heights);

    }

    void Update()
    {
        SetTerrainHeights();
    }


}