Load .obj and .mtl in Unity at runtime

UnityObjectLoader

Load .obj and .mtl in Unity at runtime

Demo.cs

using UnityEngine;
using System.Collections;

public class Manager : MonoBehaviour {

	public GameObject model;

	void Start () {
		ObjectLoader loader = model.AddComponent <ObjectLoader> ();
		loader.Load (@"/model/path/", "model.obj");
	}
}

FileReader.cs

/*
 * The .obj and .mtl files must follow Wavefront OBJ Specifications.
 *
 * OBJ Supported List
 *
 *   Vertex Data
 *     - v  Geometric vertices (not support w)
 *     - vt Texture vertices (not support w)
 *     - vn Vertex normals
 *
 *   Elements
 *     - f Face (only support triangulate faces)
 *
 *   Grouping
 *     - o Object name
 *
 *   Display
 *     - mtllib Material library (not support multiple files)
 *     - usemtl Material name
 *
 * MTL Supported List
 *
 *   Material Name
 *     - newmtl Material name
 *
 *   Texture Map
 *     - map_Kd Texture file is linked to the diffuse (not support options)
 */

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

public class FileReader {

	public struct ObjectFile {
		public string o;
		public string mtllib;
		public List<string> usemtl;
		public List<Vector3> v;
		public List<Vector3> vn;
		public List<Vector2> vt;
		public List<List<int[]>> f;
	}

	public struct MaterialFile {
		public List<string> newmtl;
		public List<string> mapKd;
	}

	public static ObjectFile ReadObjectFile (string path) {

		ObjectFile obj = new ObjectFile ();
		string[] lines = File.ReadAllLines (path);

		obj.usemtl = new List<string> ();
		obj.v = new List<Vector3> ();
		obj.vn = new List<Vector3> ();
		obj.vt = new List<Vector2> ();
		obj.f = new List<List<int[]>> ();

		foreach (string line in lines) {
			if (line == "" || line.StartsWith ("#"))
				continue;

			string[] token = line.Split (' ');
			switch (token [0]) {

			case ("o"):
				obj.o = token [1];
				break;
			case ("mtllib"):
				obj.mtllib = token [1];
				break;
			case ("usemtl"):
				obj.usemtl.Add (token [1]);
				obj.f.Add (new List<int[]> ());
				break;
			case ("v"):
				obj.v.Add (new Vector3 (
					float.Parse (token [1]),
					float.Parse (token [2]),
					float.Parse (token [3])));
				break;
			case ("vn"):
				obj.vn.Add (new Vector3 (
					float.Parse (token [1]),
					float.Parse (token [2]),
					float.Parse (token [3])));
				break;
			case ("vt"):
				obj.vt.Add (new Vector3 (
					float.Parse (token [1]),
					float.Parse (token [2])));
				break;
			case ("f"):
				for (int i = 1; i < 4; i += 1) {
					int[] triplet = Array.ConvertAll (token [i].Split ('/'), x => {
						if (String.IsNullOrEmpty (x))
							return 0;
						return int.Parse (x);
					});
					obj.f [obj.f.Count - 1].Add (triplet);
				}
				break;
			}
		}

		return obj;
	}

	public static MaterialFile ReadMaterialFile (string path) {

		MaterialFile mtl = new MaterialFile ();
		string[] lines = File.ReadAllLines (path);

		mtl.newmtl = new List<string> ();
		mtl.mapKd = new List<string> ();

		foreach (string line in lines) {
			if (line == "" || line.StartsWith ("#"))
				continue;

			string[] token = line.Split (' ');
			switch (token [0]) {

			case ("newmtl"):
				mtl.newmtl.Add (token [1]);
				break;
			case ("map_Kd"):
				mtl.mapKd.Add (token [1]);
				break;
			}
		}

		return mtl;
	}
}

ObjectLoader.cs

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

public class ObjectLoader : MonoBehaviour {

	public string directoryPath;
	public bool isLoaded;

	void Awake () {
		isLoaded = true;
	}

	public void Load (string path, string filename) {
		if (!isLoaded)
			return;

		directoryPath = path;
		StartCoroutine (ConstructModel (filename));
	}

	IEnumerator ConstructModel (string filename) {

		isLoaded = false;

		FileReader.ObjectFile obj = FileReader.ReadObjectFile (directoryPath + filename);
		FileReader.MaterialFile mtl = FileReader.ReadMaterialFile (directoryPath + obj.mtllib);

		MeshFilter filter = gameObject.AddComponent<MeshFilter> ();
		MeshRenderer renderer = gameObject.AddComponent<MeshRenderer> ();

		filter.mesh = PopulateMesh (obj);
		renderer.materials = DefineMaterial (obj, mtl);

		isLoaded = true;
		yield return null;
	}

	Mesh PopulateMesh (FileReader.ObjectFile obj) {

		Mesh mesh = new Mesh ();

		List<int[]> triplets = new List<int[]> ();
		List<int> submeshes = new List<int> ();

		for (int i = 0; i < obj.f.Count; i += 1) {
			for (int j = 0; j < obj.f [i].Count; j += 1) {
				triplets.Add (obj.f [i] [j]);
			}
			submeshes.Add (obj.f [i].Count);
		}

		Vector3[] vertices = new Vector3[triplets.Count];
		Vector3[] normals = new Vector3[triplets.Count];
		Vector2[] uvs = new Vector2[triplets.Count];

		for (int i = 0; i < triplets.Count; i += 1) {
			vertices [i] = obj.v [triplets [i] [0] - 1];
			normals [i] = obj.vn [triplets [i] [2] - 1];
			if (triplets [i] [1] > 0)
				uvs [i] = obj.vt [triplets [i] [1] - 1];
		}

		mesh.name = obj.o;
		mesh.vertices = vertices;
		mesh.normals = normals;
		mesh.uv = uvs;
		mesh.subMeshCount = submeshes.Count;

		int vertex = 0;
		for (int i = 0; i < submeshes.Count; i += 1) {
			int[] triangles = new int[submeshes [i]];
			for (int j = 0; j < submeshes [i]; j += 1) {
				triangles [j] = vertex;
				vertex += 1;
			}
			mesh.SetTriangles (triangles, i);
		}

		mesh.RecalculateBounds ();
		mesh.Optimize ();

		return mesh;
	}

	Material[] DefineMaterial (FileReader.ObjectFile obj, FileReader.MaterialFile mtl) {

		Material[] materials = new Material[obj.usemtl.Count];

		for (int i = 0; i < obj.usemtl.Count; i += 1) {
			int index = mtl.newmtl.IndexOf (obj.usemtl [i]);

			Texture2D texture = new Texture2D (1, 1);
			texture.LoadImage (File.ReadAllBytes (directoryPath + mtl.mapKd [index]));

			materials [i] = new Material (Shader.Find ("Diffuse"));
			materials [i].name = mtl.newmtl [index];
			materials [i].mainTexture = texture;
		}

		return materials;
	}
}

Thank you a billion times over. I had to make some changes to this to make it work in my unity project, such as adding multi-object support, but without this code, I wouldn't have been able to add a vital feature to my game. Thank you. Thank you. Thank you.