obj模型
helloz 2/7/2025 Unity3dmesh
obj格式
OBJ是一种开放的3D模型文件格式。
支持内容
obj 文件，3dmax 支持导出*.obj文件，同时导出 *.mtl，主要是存储贴图、材质等信息
OBJ文件：
- 主要支持多边形（Polygons）模型，包括三角形、四边形等，也可以表示直线（Lines）和自由形态曲线（Free-form Curves）。
- 支持法线和贴图坐标，但贴图需要手动重新指认。
- 不包含动画、材质特性、贴图路径、动力学、粒子、蒙皮等信息。
FBX文件：
- 支持所有主要的三维数据元素以及二维、音频和视频媒体元素。
- 包含动画、材质特性、贴图、骨骼动画、灯光、摄像机等信息。
- 支持多边形（Polygons）、曲线（Curves）、表面（Surfaces）等。
结构简单，没有复杂的层级结构
obj文件内容
# 3ds Max Wavefront OBJ Exporter v0.99 - (c)2007 guruware
# 创建的文件:07.02.2025 16:46:31
mtllib 无标题.mtl
#
# object Box001
#
v -4.1020 0.0000 -17.7684
v -4.1020 0.0000 -37.0538
v 4.4456 0.0000 -37.0538
v 4.4456 0.0000 -17.7684
v -4.1020 4.0289 -17.7684
v 4.4456 4.0289 -17.7684
v 4.4456 4.0289 -37.0538
v -4.1020 4.0289 -37.0538
# 8 vertices
vn -0.5774 -0.5774 0.5774
vn -0.5774 -0.5774 -0.5774
vn 0.5774 -0.5774 -0.5774
vn 0.5774 -0.5774 0.5774
vn -0.5774 0.5774 0.5774
vn 0.5774 0.5774 0.5774
vn 0.5774 0.5774 -0.5774
vn -0.5774 0.5774 -0.5774
# 8 vertex normals
vt 1.0000 0.0000 0.0000
vt 1.0000 1.0000 0.0000
vt 0.0000 1.0000 0.0000
vt 0.0000 0.0000 0.0000
# 4 texture coords
o Box001
g Box001
usemtl wire_168183223
s 2
f 1/1/1 2/2/2 3/3/3 4/4/4
s 4
f 5/4/5 6/1/6 7/2/7 8/3/8
s 8
f 1/4/1 4/1/4 6/2/6 5/3/5
s 16
f 4/4/4 3/1/3 7/2/7 6/3/6
s 32
f 3/4/3 2/1/2 8/2/8 7/3/7
s 64
f 2/4/2 1/1/1 5/2/5 8/3/8
# 6 polygons
#
# object Box002
#
v 2.5366 0.0000 3.8365
v 2.5366 0.0000 -4.8824
v 9.3654 0.0000 -4.8824
v 9.3654 0.0000 3.8365
v 2.5366 4.0207 3.8365
v 9.3654 4.0207 3.8365
v 9.3654 4.0207 -4.8824
v 2.5366 4.0207 -4.8824
# 8 vertices
vn -0.5774 -0.5774 0.5774
vn -0.5774 -0.5774 -0.5774
vn 0.5774 -0.5774 -0.5774
vn 0.5774 -0.5774 0.5774
vn -0.5774 0.5774 0.5774
vn 0.5774 0.5774 0.5774
vn 0.5774 0.5774 -0.5774
vn -0.5774 0.5774 -0.5774
# 8 vertex normals
vt 1.0000 0.0000 0.0000
vt 1.0000 1.0000 0.0000
vt 0.0000 1.0000 0.0000
vt 0.0000 0.0000 0.0000
# 4 texture coords
o Box002
g Box001/Box002
usemtl wire_207171210
s 2
f 9/5/9 10/6/10 11/7/11 12/8/12
s 4
f 13/8/13 14/5/14 15/6/15 16/7/16
s 8
f 9/8/9 12/5/12 14/6/14 13/7/13
s 16
f 12/8/12 11/5/11 15/6/15 14/7/14
s 32
f 11/8/11 10/5/10 16/6/16 15/7/15
s 64
f 10/8/10 9/5/9 13/6/13 16/7/16
# 6 polygons
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帮助：
3D模型obj文件格式
https://zhuanlan.zhihu.com/p/626883173
unity 案例
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
using UnityEngine;
using UnityEngine.Rendering;
public class MeshConvertObj : MonoBehaviour
{
public Mesh meshToExport;
public string filePath = "Assets/SceneBake/ExportedMesh.obj";
void Start()
{
var meshFilter = GetComponent<MeshFilter>();
using (StreamWriter streamWriter = new StreamWriter(filePath))
{
streamWriter.Write(MeshToString(meshFilter, new Vector3(-1f, 1f, 1f)));
streamWriter.Close();
}
meshToExport = Parse(filePath);
}
private string MeshToString(MeshFilter mf, Vector3 scale)
{
Mesh mesh = mf.mesh;
Material[] sharedMaterials = mf.GetComponent<Renderer>().sharedMaterials;
Vector2 textureOffset = mf.GetComponent<Renderer>().material.GetTextureOffset("_MainTex");
Vector2 textureScale = mf.GetComponent<Renderer>().material.GetTextureScale("_MainTex");
StringBuilder stringBuilder = new StringBuilder().Append("mtllib design.mtl")
.Append("\n")
.Append("g ")
.Append(mf.name)
.Append("\n");
Vector3[] vertices = mesh.vertices;
for (int i = 0; i < vertices.Length; i++)
{
Vector3 vector = vertices[i];
stringBuilder.Append(string.Format("v {0} {1} {2}\n", vector.x * scale.x, vector.y * scale.y,
vector.z * scale.z));
}
stringBuilder.Append("\n");
Dictionary<int, int> dictionary = new Dictionary<int, int>();
if (mesh.subMeshCount > 1)
{
int[] triangles = mesh.GetTriangles(1);
for (int j = 0; j < triangles.Length; j += 3)
{
if (!dictionary.ContainsKey(triangles[j]))
{
dictionary.Add(triangles[j], 1);
}
if (!dictionary.ContainsKey(triangles[j + 1]))
{
dictionary.Add(triangles[j + 1], 1);
}
if (!dictionary.ContainsKey(triangles[j + 2]))
{
dictionary.Add(triangles[j + 2], 1);
}
}
}
for (int num = 0; num != mesh.uv.Length; num++)
{
Vector2 vector2 = Vector2.Scale(mesh.uv[num], textureScale) + textureOffset;
if (dictionary.ContainsKey(num))
{
stringBuilder.Append(string.Format("vt {0} {1}\n", mesh.uv[num].x, mesh.uv[num].y));
}
else
{
stringBuilder.Append(string.Format("vt {0} {1}\n", vector2.x, vector2.y));
}
}
for (int k = 0; k < mesh.subMeshCount; k++)
{
stringBuilder.Append("\n");
if (k == 0)
{
stringBuilder.Append("usemtl ").Append("Material_design").Append("\n");
}
if (k == 1)
{
stringBuilder.Append("usemtl ").Append("Material_logo").Append("\n");
}
int[] triangles2 = mesh.GetTriangles(k);
for (int l = 0; l < triangles2.Length; l += 3)
{
stringBuilder.Append(string.Format("f {0}/{0} {1}/{1} {2}/{2}\n", triangles2[l] + 1,
triangles2[l + 2] + 1, triangles2[l + 1] + 1));
}
}
return stringBuilder.ToString();
}
public Mesh Parse(string url)
{
Mesh mesh = new Mesh();
List<Vector3> vts = new List<Vector3>();
List<Vector2> uvs = new List<Vector2>();
List<Vector3> normals = new List<Vector3>();
List<int> tris = new List<int>();
StreamReader sr = new StreamReader(url);
while (!sr.EndOfStream)
{
string line = sr.ReadLine();
string[] split = line.Split(' ');
switch (split[0])
{
case "o":
mesh.name = split[1];
break;
case "v":
{
float x = float.Parse(split[1]);
float y = float.Parse(split[2]);
float z = float.Parse(split[3]);
vts.Add(new Vector3(x, y, z));
}
break;
case "vn":
{
float x = float.Parse(split[1]);
float y = float.Parse(split[2]);
float z = float.Parse(split[3]);
normals.Add(new Vector3(x, y, z));
}
break;
case "vt":
{
float x = float.Parse(split[1]);
float y = float.Parse(split[2]);
uvs.Add(new Vector2(x, y));
}
break;
case "f":
{
for (int i = 1; i < split.Length; ++i)
{
string[] sp = split[i].Split('/');
try
{
tris.Add(int.Parse(sp[0]) - 1);
}
catch (Exception e)
{
Debug.LogError(split[i]);
Debug.LogError(sp.Length);
Debug.LogError(e);
}
}
}
break;
default:
break;
}
}
mesh.vertices = vts.ToArray();
mesh.uv = uvs.ToArray();
mesh.normals = normals.ToArray();
mesh.triangles = tris.ToArray();
return mesh;
}
}
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