ObjExporter

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Author: KeliHlodversson

Contents

Description

This is a simple utility class for generating basic obj files from a mesh object. The obj file format was gleaned from various sites found through google like this one

Usage

Either call ObjExporter.MeshToString() to generate a text string containing the obj file or ObjExporter.MeshToFile() to save it directly to a file.

ObjExporter.cs

using UnityEngine;
using System.Collections;
using System.IO;
using System.Text;
 
public class ObjExporter {
 
    public static string MeshToString(MeshFilter mf) {
        Mesh m = mf.mesh;
        Material[] mats = mf.renderer.sharedMaterials;
 
        StringBuilder sb = new StringBuilder();
 
        sb.Append("g ").Append(mf.name).Append("\n");
        foreach(Vector3 v in m.vertices) {
            sb.Append(string.Format("v {0} {1} {2}\n",v.x,v.y,v.z));
        }
        sb.Append("\n");
        foreach(Vector3 v in m.normals) {
            sb.Append(string.Format("vn {0} {1} {2}\n",v.x,v.y,v.z));
        }
        sb.Append("\n");
        foreach(Vector3 v in m.uv) {
            sb.Append(string.Format("vt {0} {1}\n",v.x,v.y));
        }
        for (int material=0; material < m.subMeshCount; material ++) {
            sb.Append("\n");
            sb.Append("usemtl ").Append(mats[material].name).Append("\n");
            sb.Append("usemap ").Append(mats[material].name).Append("\n");
 
            int[] triangles = m.GetTriangles(material);
            for (int i=0;i<triangles.Length;i+=3) {
                sb.Append(string.Format("f {0}/{0}/{0} {1}/{1}/{1} {2}/{2}/{2}\n", 
                    triangles[i]+1, triangles[i+1]+1, triangles[i+2]+1));
            }
        }
        return sb.ToString();
    }
 
    public static void MeshToFile(MeshFilter mf, string filename) {
        using (StreamWriter sw = new StreamWriter(filename)) 
        {
            sw.Write(MeshToString(mf));
        }
    }
}


EditorObjExporter.cs

/*
Based on ObjExporter.cs, this "wrapper" lets you export to .OBJ directly from the editor menu.
 
This should be put in your "Editor"-folder. Use by selecting the objects you want to export, and select
the appropriate menu item from "Custom->Export". Exported models are put in a folder called
"ExportedObj" in the root of your Unity-project. Textures should also be copied and placed in the
same folder.
N.B. there may be a bug so if the custom option doesn't come up refer to this thread http://answers.unity3d.com/questions/317951/how-to-use-editorobjexporter-obj-saving-script-fro.html 
 
Updated for Unity 5.3
*/
 
using UnityEngine;
using UnityEditor;
using UnityEditor.SceneManagement;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System;
 
struct ObjMaterial
{
	public string name;
	public string textureName;
}
 
public class EditorObjExporter : ScriptableObject
{
	private static int vertexOffset = 0;
	private static int normalOffset = 0;
	private static int uvOffset = 0;
 
 
	//User should probably be able to change this. It is currently left as an excercise for
	//the reader.
	private static string targetFolder = "ExportedObj";
 
 
	private static string MeshToString(MeshFilter mf, Dictionary<string, ObjMaterial> materialList) 
	{
		Mesh m = mf.sharedMesh;
		Material[] mats = mf.GetComponent<Renderer>().sharedMaterials;
 
		StringBuilder sb = new StringBuilder();
 
		sb.Append("g ").Append(mf.name).Append("\n");
		foreach(Vector3 lv in m.vertices) 
		{
			Vector3 wv = mf.transform.TransformPoint(lv);
 
			//This is sort of ugly - inverting x-component since we're in
			//a different coordinate system than "everyone" is "used to".
			sb.Append(string.Format("v {0} {1} {2}\n",-wv.x,wv.y,wv.z));
		}
		sb.Append("\n");
 
		foreach(Vector3 lv in m.normals) 
		{
			Vector3 wv = mf.transform.TransformDirection(lv);
 
			sb.Append(string.Format("vn {0} {1} {2}\n",-wv.x,wv.y,wv.z));
		}
		sb.Append("\n");
 
		foreach(Vector3 v in m.uv) 
		{
			sb.Append(string.Format("vt {0} {1}\n",v.x,v.y));
		}
 
		for (int material=0; material < m.subMeshCount; material ++) {
			sb.Append("\n");
			sb.Append("usemtl ").Append(mats[material].name).Append("\n");
			sb.Append("usemap ").Append(mats[material].name).Append("\n");
 
			//See if this material is already in the materiallist.
			try
			{
				ObjMaterial objMaterial = new ObjMaterial();
 
				objMaterial.name = mats[material].name;
 
				if (mats[material].mainTexture)
					objMaterial.textureName = AssetDatabase.GetAssetPath(mats[material].mainTexture);
				else 
					objMaterial.textureName = null;
 
				materialList.Add(objMaterial.name, objMaterial);
			}
			catch (ArgumentException)
			{
				//Already in the dictionary
			}
 
 
			int[] triangles = m.GetTriangles(material);
			for (int i=0;i<triangles.Length;i+=3) 
			{
				//Because we inverted the x-component, we also needed to alter the triangle winding.
				sb.Append(string.Format("f {1}/{1}/{1} {0}/{0}/{0} {2}/{2}/{2}\n", 
					triangles[i]+1 + vertexOffset, triangles[i+1]+1 + normalOffset, triangles[i+2]+1 + uvOffset));
			}
		}
 
		vertexOffset += m.vertices.Length;
		normalOffset += m.normals.Length;
		uvOffset += m.uv.Length;
 
		return sb.ToString();
	}
 
	private static void Clear()
	{
		vertexOffset = 0;
		normalOffset = 0;
		uvOffset = 0;
	}
 
	private static Dictionary<string, ObjMaterial> PrepareFileWrite()
	{
		Clear();
 
		return new Dictionary<string, ObjMaterial>();
	}
 
	private static void MaterialsToFile(Dictionary<string, ObjMaterial> materialList, string folder, string filename)
	{
		using (StreamWriter sw = new StreamWriter(folder + Path.PathSeparator + filename + ".mtl")) 
		{
			foreach( KeyValuePair<string, ObjMaterial> kvp in materialList )
			{
				sw.Write("\n");
				sw.Write("newmtl {0}\n", kvp.Key);
				sw.Write("Ka  0.6 0.6 0.6\n");
				sw.Write("Kd  0.6 0.6 0.6\n");
				sw.Write("Ks  0.9 0.9 0.9\n");
				sw.Write("d  1.0\n");
				sw.Write("Ns  0.0\n");
				sw.Write("illum 2\n");
 
				if (kvp.Value.textureName != null)
				{
					string destinationFile = kvp.Value.textureName;
 
 
					int stripIndex = destinationFile.LastIndexOf(Path.PathSeparator);
 
					if (stripIndex >= 0)
						destinationFile = destinationFile.Substring(stripIndex + 1).Trim();
 
 
					string relativeFile = destinationFile;
 
					destinationFile = folder + Path.PathSeparator + destinationFile;
 
					Debug.Log("Copying texture from " + kvp.Value.textureName + " to " + destinationFile);
 
					try
					{
						//Copy the source file
						File.Copy(kvp.Value.textureName, destinationFile);
					}
					catch
					{
 
					}	
 
 
					sw.Write("map_Kd {0}", relativeFile);
				}
 
				sw.Write("\n\n\n");
			}
		}
	}
 
	private static void MeshToFile(MeshFilter mf, string folder, string filename) 
	{
		Dictionary<string, ObjMaterial> materialList = PrepareFileWrite();
 
		using (StreamWriter sw = new StreamWriter(folder +Path.PathSeparator + filename + ".obj")) 
		{
			sw.Write("mtllib ./" + filename + ".mtl\n");
 
			sw.Write(MeshToString(mf, materialList));
		}
 
		MaterialsToFile(materialList, folder, filename);
	}
 
	private static void MeshesToFile(MeshFilter[] mf, string folder, string filename) 
	{
		Dictionary<string, ObjMaterial> materialList = PrepareFileWrite();
 
		using (StreamWriter sw = new StreamWriter(folder +Path.PathSeparator + filename + ".obj")) 
		{
			sw.Write("mtllib ./" + filename + ".mtl\n");
 
			for (int i = 0; i < mf.Length; i++)
			{
				sw.Write(MeshToString(mf[i], materialList));
			}
		}
 
		MaterialsToFile(materialList, folder, filename);
	}
 
	private static bool CreateTargetFolder()
	{
		try
		{
			System.IO.Directory.CreateDirectory(targetFolder);
		}
		catch
		{
			EditorUtility.DisplayDialog("Error!", "Failed to create target folder!", "");
			return false;
		}
 
		return true;
	}
 
	[MenuItem ("Custom/Export/Export all MeshFilters in selection to separate OBJs")]
	static void ExportSelectionToSeparate()
	{
		if (!CreateTargetFolder())
			return;
 
		Transform[] selection = Selection.GetTransforms(SelectionMode.Editable | SelectionMode.ExcludePrefab);
 
		if (selection.Length == 0)
		{
			EditorUtility.DisplayDialog("No source object selected!", "Please select one or more target objects", "");
			return;
		}
 
		int exportedObjects = 0;
 
		for (int i = 0; i < selection.Length; i++)
		{
			Component[] meshfilter = selection[i].GetComponentsInChildren(typeof(MeshFilter));
 
			for (int m = 0; m < meshfilter.Length; m++)
			{
				exportedObjects++;
				MeshToFile((MeshFilter)meshfilter[m], targetFolder, selection[i].name + "_" + i + "_" + m);
			}
		}
 
		if (exportedObjects > 0)
			EditorUtility.DisplayDialog("Objects exported", "Exported " + exportedObjects + " objects", "");
		else
			EditorUtility.DisplayDialog("Objects not exported", "Make sure at least some of your selected objects have mesh filters!", "");
	}
 
	[MenuItem ("Custom/Export/Export whole selection to single OBJ")]
	static void ExportWholeSelectionToSingle()
	{
		if (!CreateTargetFolder())
			return;
 
 
		Transform[] selection = Selection.GetTransforms(SelectionMode.Editable | SelectionMode.ExcludePrefab);
 
		if (selection.Length == 0)
		{
			EditorUtility.DisplayDialog("No source object selected!", "Please select one or more target objects", "");
			return;
		}
 
		int exportedObjects = 0;
 
		ArrayList mfList = new ArrayList();
 
		for (int i = 0; i < selection.Length; i++)
		{
			Component[] meshfilter = selection[i].GetComponentsInChildren(typeof(MeshFilter));
 
			for (int m = 0; m < meshfilter.Length; m++)
			{
				exportedObjects++;
				mfList.Add(meshfilter[m]);
			}
		}
 
		if (exportedObjects > 0)
		{
			MeshFilter[] mf = new MeshFilter[mfList.Count];
 
			for (int i = 0; i < mfList.Count; i++)
			{
				mf[i] = (MeshFilter)mfList[i];
			}
 
			string filename = EditorSceneManager.GetActiveScene().name + "_" + exportedObjects;
 
			int stripIndex = filename.LastIndexOf(Path.PathSeparator);
 
			if (stripIndex >= 0)
				filename = filename.Substring(stripIndex + 1).Trim();
 
			MeshesToFile(mf, targetFolder, filename);
 
 
			EditorUtility.DisplayDialog("Objects exported", "Exported " + exportedObjects + " objects to " + filename, "");
		}
		else
			EditorUtility.DisplayDialog("Objects not exported", "Make sure at least some of your selected objects have mesh filters!", "");
	}
 
 
 
	[MenuItem ("Custom/Export/Export each selected to single OBJ")]
	static void ExportEachSelectionToSingle()
	{
		if (!CreateTargetFolder())
			return;
 
		Transform[] selection = Selection.GetTransforms(SelectionMode.Editable | SelectionMode.ExcludePrefab);
 
		if (selection.Length == 0)
		{
			EditorUtility.DisplayDialog("No source object selected!", "Please select one or more target objects", "");
			return;
		}
 
		int exportedObjects = 0;
 
 
		for (int i = 0; i < selection.Length; i++)
		{
			Component[] meshfilter = selection[i].GetComponentsInChildren(typeof(MeshFilter));
 
			MeshFilter[] mf = new MeshFilter[meshfilter.Length];
 
			for (int m = 0; m < meshfilter.Length; m++)
			{
				exportedObjects++;
				mf[m] = (MeshFilter)meshfilter[m];
			}
 
			MeshesToFile(mf, targetFolder, selection[i].name + "_" + i);
		}
 
		if (exportedObjects > 0)
		{
			EditorUtility.DisplayDialog("Objects exported", "Exported " + exportedObjects + " objects", "");
		}
		else
			EditorUtility.DisplayDialog("Objects not exported", "Make sure at least some of your selected objects have mesh filters!", "");
	}
 
}
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