Using Perlin Noise across multiple Unity Terrain objects

Question

I have a class project in which we are supposed to use Unities Terrain 3D objects and create a 3x3 smoothly generated terrain. For this we have been told to create a central Terrain the has adjacent terrains in the 8 cardinal directions. I have gotten the Perlin Noise to work through this method

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

public class TerrainNoiseGeneration : MonoBehaviour
{

private TerrainData myTerrainData;
public Vector3 worldSize;
public int resolution = 129;
private float userInput = (float)4.2;
public float offsetX;
public float offsetZ;

// Start is called before the first frame update
void Start()
{
    myTerrainData = gameObject.GetComponent<TerrainCollider>().terrainData;
    worldSize = new Vector3(100, 50, 100);
    myTerrainData.size = worldSize;
    myTerrainData.heightmapResolution = resolution;
    float[,] heightArray = new float[resolution, resolution];
    heightArray = PerlinNoise(userInput, offsetX, offsetZ);
    myTerrainData.SetHeights(0, 0, heightArray);
}

// Update is called once per frame
void Update()
{
    float[,] heightArray = new float[resolution, resolution];
    heightArray = PerlinNoise(userInput, offsetX, offsetZ);
    myTerrainData.SetHeights(0, 0, heightArray);
}

float[,] PerlinNoise(float userInput, float offsetX, float offsetZ)
{
    float[,] heights = new float[resolution, resolution];

    for (int z = 0; z < resolution; z++)
    {
        for (int x = 0; x < resolution; x++)
        {
            float nx = (x + offsetX) / resolution * userInput;
            float ny = (z + offsetZ) / resolution * userInput;
            heights[z, x] = Mathf.PerlinNoise(nx, ny);
        }
    }

    return heights;
}

This code allows me to Generate a smooth terrain in the first Terrain object but when I try entering the offset values so that the edges can line-up they do not have the same values.

I would appreciate any assistance on this issue as I have tried a lot of different solutions, none of which are working

Update: I was able to solve the problem with a rather simple solution of the fact that I needed to use my resolution as the offset not the distance between the terrains

Answer 1

I needed to set the OffsetX and OffsetZ equal to that of their respective resolution positions instead of their unity positions.

For example my terrains are 100x100 so I was setting offset to 100 or -100 depending on its location but instead I needed to use 128 or -128 to keep it in line with the resolution