obj 模型中纹理的 Opengl 问题

Question

我在 OpenGL 中编写小程序，但遇到问题（纹理倾斜，我不知道为什么，该模型在另一个 obj 查看器中工作） 我有什么： http://img696.imageshack.us/i/obrazo.png/ 我想要什么 http://img88.imageshack.us/i/obraz2d.jpg/ 项目代码（我使用 Devil 来表示图像）：

#pragma once

#include <windows.h>              
#define GLUT_DISABLE_ATEXIT_HACK  
#include <glut.h>
#include <GL/glu.h>
#include <GL/gl.h>
#include <GL/GLEXT.h>
#include <iostream>
#include <cmath>
#include <IL/il.h>
#include <vector>
#include <fstream>
#include <string>
#include <cstdlib>
#include <sstream>
#include <clocale>

class TextureManager
{
    struct TextureInfo{
        std::string name;
        GLuint image;
    };

private:
    std::vector<TextureInfo> textures;
public:
    TextureManager(void);
    ~TextureManager(void);

    bool AddTexture(std::string name, std::string fileName);
    int GetTexture(std::string name);
};
TextureManager::TextureManager(void)
{
    ilInit();
}

TextureManager::~TextureManager(void)
{

}

bool TextureManager::AddTexture(std::string name, std::string fileName)
{
    bool success;
    ILuint texId;
    GLuint image;
    ilGenImages(1, &texId);
    ilBindImage(texId);
    success = ilLoadImage((WCHAR*)fileName.c_str());
    if(success)
    {
        success = ilConvertImage(IL_RGB, IL_UNSIGNED_BYTE); 
        if(!success)
        {   
            return false;
        }
    }
    else
    {
        return false;
    }

    glGenTextures(1, &image);
    glBindTexture(GL_TEXTURE_2D, image);

    glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_NEAREST_MIPMAP_LINEAR);
    gluBuild2DMipmaps( GL_TEXTURE_2D, 3, ilGetInteger(IL_IMAGE_WIDTH), ilGetInteger(IL_IMAGE_HEIGHT),GL_RGB, GL_UNSIGNED_BYTE, ilGetData());
    ilDeleteImages(1, &texId); 


    TextureInfo ti;
    ti.name = name;
    ti.image = image;
    textures.push_back(ti);

    return true;
}
int TextureManager::GetTexture(std::string name)
{
    int size = textures.size();
    for(int i=0;i<size;i++)
    {
        if(textures.at(i).name.compare(name) == 0)
        {
            return textures.at(i).image;
        }
    }

    return -1;
}
using namespace std;

TextureManager tm;

struct Point
{
    double x,y,z;
};
struct Normal
{
    double x,y,z;
};
struct Triangle
{
    int a,b,c;
    int at,bt,ct;
    int an,bn,cn;

};
struct TexCord
{
    float x,y;
};
vector<Point> points;
vector<Normal> normals;
vector<Triangle> triangles;
vector<TexCord> texcords;
int w,h;
double j = 0.0;
double k = 0.0;
int mode = 1;
bool showNormals = false;
void setCamera(double eyex,double eyey, double eyez, double centerx, double centery, double centerz)
{
    gluLookAt(eyex,eyey,eyez,centerx,centery,centerz,0,1,0);
}

void DrawPoint(TexCord tc,Point p,Normal n)
{
    glTexCoord2f(tc.x,tc.y);
    glNormal3f(n.x,n.y,n.z); 
    glVertex3f(p.x,p.y,p.z);
}

void DrawNormal(Point p,Normal n)
{
    glPushMatrix();
    glTranslated(p.x,p.y,p.z);
    glBegin(GL_LINES);
    glVertex3f(0,0,0);
    glVertex3f(n.x*2,n.y*2,n.z*2);
    glEnd();
    glPopMatrix();
}

void processNormalKeys(unsigned char key, int x, int y) {

    if (key == 27) 
        exit(0);
    if (key == 'q')
    {
        mode = 0;
    }
    if (key == 'w')
    {
        mode = 1;
    }
    if (key == 'a')
    {
        k -= 0.1;
    }
    if (key == 's')
    {
        k += 0.1;
    }   
    if (key == 'z')
    {
        j -= 0.1;
    }
    if (key == 'x')
    {
        j += 0.1;
    }   
    if (key == 'n')
    {
        if(showNormals == true)
        {
            showNormals = false;
        }
        else
        {
            showNormals = true;
        }
    }
    glutPostRedisplay();
}


void renderScene(void) {
    //j+=0.0005;
    glMatrixMode(GL_PROJECTION); 
        glLoadIdentity(); 
    gluPerspective(60, (GLfloat)w / (GLfloat)h, 1.0, 100.0); 
    setCamera(15*sin(j),15*cos(k),15*cos(j)*sin(k),0,0,0);
    glMatrixMode(GL_MODELVIEW);  

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_LIGHTING);
    //glEnable(GL_LIGHT0);

    float ambient[]={ 1.0, 1.0, 1.0, 0.0};
    float diffuse[]={1.0, 1.0, 1.0, 1.0};
    float position[]={25.0,25.0, 25.0, 1.0};


    glLightfv(GL_LIGHT0, GL_AMBIENT, diffuse);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
    glLightfv(GL_LIGHT0, GL_POSITION, position);

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, tm.GetTexture("tex"));
    if(mode ==  0 )
    {
    glBegin(GL_TRIANGLES);
    }
    else
    {
    glBegin(GL_LINES);
    }
    for(int i=0;i<triangles.size();i++)
    {
        //double r =  rand()/(double)RAND_MAX;
        //glColor3f(r,r,r);


        DrawPoint(texcords[triangles[i].ct-1],points[triangles[i].c-1],normals[triangles[i].cn-1]);
        DrawPoint(texcords[triangles[i].bt-1],points[triangles[i].b-1],normals[triangles[i].bn-1]);
        DrawPoint(texcords[triangles[i].at-1],points[triangles[i].a-1],normals[triangles[i].an-1]);
    }
    glEnd();
    glDisable(GL_TEXTURE_2D);
    if(showNormals == true)
    {
        glDisable(GL_LIGHTING);
        glDisable(GL_LIGHT0);
        glColor3f(1,0.5f,0.25f);
        for(int i = 0;i<points.size();i++)
        {
            DrawNormal(points[i],normals[i]);
        }
    }
    glFlush();
    glutSwapBuffers();
}
void reshape (int width, int height) {  
    w = width; h = height;
    glViewport(0, 0, (GLsizei)width, (GLsizei)height);
    glMatrixMode(GL_PROJECTION);  
    glLoadIdentity(); 
    gluPerspective(60, (GLfloat)width / (GLfloat)height, 1.0, 100.0); 

    glMatrixMode(GL_MODELVIEW);   

}  

void update(int value) {
    j += 0.1f;


    glutPostRedisplay(); //Tell GLUT that the scene has changed

    //Tell GLUT to call update again in 25 milliseconds
   // glutTimerFunc(100, update, 0);
}

int main(int argc, char **argv) {



    vector<Normal> *nn = &normals;
    vector<Point> *pp = &points;
    vector<Triangle> *tt = &triangles;
    vector<TexCord> *ttcc = &texcords;
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100,100);
    glutInitWindowSize(320,320);
    glutCreateWindow("Model view");


    glutKeyboardFunc(processNormalKeys);


    glutDisplayFunc(renderScene);
    //glutIdleFunc(renderScene);
    glutReshapeFunc(reshape);

        ifstream f;
    string cmd;

    f.open ("model.obj");




     if (f.is_open())
  { 
    while(!f.eof())
    {
        f>>cmd;
        if(cmd=="v")
        {
            Point p;
            f>>p.x;
            f>>p.y;
            f>>p.z;
            points.push_back(p);
        }
        if(cmd=="vn")
        {
            Normal n;
            f>>n.x;
            f>>n.y;
            f>>n.z;
            normals.push_back(n);
        }
        if(cmd=="vt")
        {
            TexCord tc;
            f>>tc.x;
            f>>tc.y;
            texcords.push_back(tc);
        }
        if(cmd=="f")
        {

            Triangle t;
            string str;
            string pointStr,normalStr,cordStr;
            string delimeter("/");
            int pos,pos2;
            stringstream ss (stringstream::in | stringstream::out);

            f>>str;
            pos = str.find(delimeter);

            pointStr = str.substr(0,pos);
            cordStr = str.substr(pos+delimeter.length());
            pos2 = cordStr.find(delimeter);
            normalStr = cordStr.substr(pos2+delimeter.length());
            cordStr = cordStr.substr(0,pos2);
            ss<<pointStr;
            ss>>t.a;
            ss.clear();
            ss<<normalStr;
            ss>>t.an;
            ss.clear();
            ss<<cordStr;
            ss>>t.at;
            ss.clear();

            f>>str;
            pos = str.find(delimeter);

            pointStr = str.substr(0,pos);
            cordStr = str.substr(pos+delimeter.length());
            pos2 = cordStr.find(delimeter);
            normalStr = cordStr.substr(pos2+delimeter.length());
            cordStr = cordStr.substr(0,pos2);
            ss<<pointStr;
            ss>>t.b;
            ss.clear();
            ss<<normalStr;
            ss>>t.bn;
            ss.clear();
            ss<<cordStr;
            ss>>t.bt;
            ss.clear();

            f>>str;
            pos = str.find(delimeter);

            pointStr = str.substr(0,pos);
            cordStr = str.substr(pos+delimeter.length());
            pos2 = cordStr.find(delimeter);
            normalStr = cordStr.substr(pos2+delimeter.length());
            cordStr = cordStr.substr(0,pos2);
            ss<<pointStr;
            ss>>t.c;
            ss.clear();
            ss<<normalStr;
            ss>>t.cn;
            ss.clear();
            ss<<cordStr;
            ss>>t.ct;
            ss.clear();

            triangles.push_back(t);

        }
        cmd = "";
    }

    f.close();  }
     tm.AddTexture("tex","texture.png");
    //glutTimerFunc(100, update, 0); 

    glutMainLoop();
}

Answer 1

我想我只需在 points 向量的开头推入一个虚拟点，并将点引用保留为基于 1 的。我还要去掉 while (!in.eof()) ，它通常会读取最后一行两次。最后，我将使用 operator>> 的一些重载来读取大部分数据，给出如下所示的结果：

#include <locale>
#include <vector>
#include <sstream>
#include <string>
#include <fstream>

/* change to "#if 0" for normal compilation: */
#if 1
struct Triangle { float a, an, atc, b, bn, btc, c, cn, ctc; };
struct Vector2d { float x, y; };
struct Vector3d { float x, y, z; };

std::vector<Triangle> triangles;
std::vector<Vector3d> points, normals;
std::vector<Vector2d> texcords;
#endif

namespace { 
struct slashsep: std::ctype<char> {
    slashsep(): std::ctype<char>(get_table()) {}

    static std::ctype_base::mask const* get_table() {
        static std::vector<std::ctype_base::mask> 
            rc(std::ctype<char>::table_size,std::ctype_base::mask());

        rc['/'] = std::ctype_base::space; // Treat '/' as a separator between numbers.
        rc[' '] = std::ctype_base::space;
        rc['\n'] = std::ctype_base::space;
        rc['\t'] = std::ctype_base::space;
        return &rc[0];
    }
};

std::istream &operator>>(std::istream &in, Triangle &triangle) { 
    std::string str;

    std::getline(in, str);
    std::istringstream temp(str);
    slashsep loc;
    temp.imbue(std::locale(std::locale(), &loc));

    temp >> triangle.a >> triangle.an >> triangle.atc;
    temp >> triangle.b >> triangle.bn >> triangle.btc;
    temp >> triangle.c >> triangle.cn >> triangle.ctc;
    return in;
}

std::istream &operator>>(std::istream &in, Vector3d &v) { 
    return in >> v.x >> v.y >> v.z;
}

std::istream &operator>>(std::istream &in, Vector2d &v) { 
    return in >> v.x >> v.y;
}
}

bool read_obj(std::string const &fileName) { 
    points.clear();
    points.push_back(Vector3d());
    triangles.clear();

    std::ifstream in(fileName.c_str());
    std::string cmd;

    if (!in.is_open())
        return false;

    while(in>>cmd) {
        if(cmd=="v") {
            Vector3d vector;
            in >> vector;
            points.push_back(vector);
        }
        if(cmd=="vt") {
            Vector2d texcord;
            in >> texcord;
            texcords.push_back(texcord);
        }
        if(cmd=="vn"){
            Vector3d normal;
            in >> normal;
            normals.push_back(normal);
        }
        if(cmd=="f") {
            Triangle triangle;
            in >> triangle;
            triangles.push_back(triangle);
        }
    }
    return true;
}

一个小要点： while using the locale to treat '/'由于数字之间的分隔符适用于您正在查看的 OBJ 的特定变体，因此它不适用于包含以下行的文件：

f a//b c//d e//f

尽管如此，总体思路（大多数使用 operator> 阅读;>) 当/如果您决定增强它以处理这种格式变体时会很好。

编辑：我想我刚刚意识到部分问题。读取脸部的代码应该是这样的：

temp >> triangle.a >> triangle.atc >> triangle.an;
temp >> triangle.b >> triangle.btc >> triangle.bn;
temp >> triangle.c >> triangle.ctc >> triangle.cn;

即，在文件中，它被排列为顶点/法线/法线，但是您的代码和我上面的先前版本尝试将其读取为顶点/法线/法线）。一旦代码按照这种方式排列，对照参考进行检查就会使问题变得相当明显。

Answer 2

好的，我修复了所有 :D:D
我做什么：
更改

glTexCoord2f(tc.x,tc.y);

为

glTexCoord2f(tc.x,1-tc.y);

，最重要的是我将图像分辨率更改为 1024x1024（我使用 mipmaping，所以我认为正确的图像分辨率很重要）
现在：
Sameone 可以解释一下为什么 lTexCoord2f(tc.x,1-tc.y);工作 ？
让每张图像的分辨率都为 2^x 重要吗？