TerrainHeightParser.Cs

using UnityEngine;
using System.IO;
using System.Text;
using System;

public class TerrainHeightParser : MonoBehaviour {

    private Terrain terrain;
    private int hmWidth;
    private int hmHeight;
    
    private string ReadFile(string fileName)
    {
        try
        {
            StreamReader reader = new StreamReader(fileName, Encoding.Default);
            return reader.ReadToEnd();
        }
        catch (Exception e)
        {
            return e.Message;
        }
    }

    void Start()
    {
        terrain = Terrain.activeTerrain;
        hmWidth = terrain.terrainData.heightmapWidth;
        hmHeight = terrain.terrainData.heightmapHeight;
        float[,] terrainHeights = terrain.terrainData.GetHeights(0, 0, hmWidth, hmHeight);
        string text = ReadFile("Assets/heightmap.txt");
        string[] lines = text.Split('\n');
        for (int y = 0; y < lines.Length; y++)
        {
            string[] heights = lines[y].Split(',');
            Debug.Log(heights.Length);
            for (int x = 0; x < heights.Length; x++)
            {
                int h = 0;
                try
                {
                    h = int.Parse(heights[x]);
                } catch (Exception ex)
                {
                    Debug.Log(ex.Message + ": " + h);
                }
                terrainHeights[x, 63 - y] = (h != 0 ? (-h / 10000F) : 0);
            }
        }
        terrain.terrainData.SetHeights(0, 0, terrainHeights);
    }
}