A Unity 5 script to load a ZX Spectrum snapshot file of Sandy White's Ant Attack 3D, extract the map, and create it in the current scene. The ANTATTAK resource is a SNA file imported into Unity. 'floor' is a GameObject for each 1x1x1 cube, textured with a stone texture. The loader creates clones of this.

MapLoader.cs

using UnityEngine;
using System.Collections;


public class MapLoader : MonoBehaviour
{

	public GameObject floor;

	bool IsBitSet (byte b, int pos)
	{
		return (b & (1 << pos)) != 0;
	}

	// Use this for initialization
	void Start ()
	{			
		TextAsset mapdata = Resources.Load ("ANTATTAK") as TextAsset;
		
		byte[] map = mapdata.bytes;
		
		for (int x=0; x<128; x++) {
			for (int z=0; z<128; z++) {			
				int n = 32795 + x * 128 + z;
				if (map [n] > 0) {				
					for (int m=0; m<6; m++) {					
						if (IsBitSet (map [n], m)) {
			
							float xx = ((float)x - 64.0f);
							float zz = ((float)z - 64.0f);
							float yy = (float)m;
						
							Instantiate (floor, new Vector3 (xx, yy, zz), Quaternion.identity);					
						}
					}
				}
			}
		}	
	}
	
	// Update is called once per frame
	void Update ()
	{
	
	}
}