Example of detection of terrain texture at position

GetMainTextureThing.cs

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

public class GetMainTextureThing : MonoBehaviour
{

    TerrainData mTerrainData;
    int alphamapWidth;
    int alphamapHeight;
    float[,,] mSplatmapData;
    int mNumTextures;

    void Start()
    {
        mTerrainData = Terrain.activeTerrain.terrainData;
        alphamapWidth = mTerrainData.alphamapWidth;
        alphamapHeight = mTerrainData.alphamapHeight;
    
        mSplatmapData = mTerrainData.GetAlphamaps(0, 0, alphamapWidth, alphamapHeight);
        mNumTextures = mSplatmapData.Length / (alphamapWidth * alphamapHeight);
    }
    
    private Vector3 ConvertToSplatMapCoordinate(Vector3 playerPos)
    {
        Vector3 vecRet = new Vector3();
        Terrain ter = Terrain.activeTerrain;
        Vector3 terPosition = ter.transform.position;
        vecRet.x = ((playerPos.x - terPosition.x) / ter.terrainData.size.x) * ter.terrainData.alphamapWidth;
        vecRet.z = ((playerPos.z - terPosition.z) / ter.terrainData.size.z) * ter.terrainData.alphamapHeight;
        return vecRet;
    }
    
    void Update()
    {
        int terrainIdx = GetActiveTerrainTextureIdx();
        name = "Current terrain: "+terrainIdx;
    }
    
    int GetActiveTerrainTextureIdx()
    {
        Vector3 playerPos = transform.position;
        Vector3 TerrainCord = ConvertToSplatMapCoordinate(playerPos);
        int ret = 0;
        float comp = 0f;
        for (int i = 0; i < mNumTextures; i++)
        {
            if (comp < mSplatmapData[(int)TerrainCord.z, (int)TerrainCord.x, i])
                comp = mSplatmapData[(int)TerrainCord.z, (int)TerrainCord.x, i];
                ret = i;
        }
        return ret;
    }
}

Thanks for sharing this! There's a bug you might want to fix:

            if (comp < mSplatmapData[(int)TerrainCord.z, (int)TerrainCord.x, i])
                ret = i;

should be

            if (comp < mSplatmapData[(int)TerrainCord.z, (int)TerrainCord.x, i]) {
                comp = mSplatmapData[(int)TerrainCord.z, (int)TerrainCord.x, i];
                ret = i;
            }

👍