使用OpenGL渲染錯誤

Question

使用谷歌等這樣的一個任務在此刻，即時導入所有vert從一個obj文件從3ds max我現在使用一個立方體，但它呈現所有的奇怪它很難解釋，但它不渲染立方體我看起來更像是一個三角形：

#include <windows.h> 
#include <GL/gl.h> 
#include <GL/glu.h> 
#include "glut.h" 
#include <istream> 
#include <iostream> 
#include <fstream> 
#include <string> 
#include <sstream> 
#include <vector> 


using namespace std; 

// structs for arrays 
struct point3D 
{ 
float x; 
float y; 
float z; 
}; 
//camera structs 
struct camera 
{ 
point3D pos; 
point3D lookAt; 
point3D up; 

}; 

//global variables 
camera cam = {0, 0, 5, 0, 0, 0, 0, 1, 0}; 

int mousex = 0; 
int mousey = 0; 
bool mouseDown=false; 


point3D v[8] = {}; 
point3D vn[6] = {}; 
point3D vt[4] = {}; 
point3D f[12][3] = {}; 

void init() 
{ 
glClearColor(0.5, 0.7, 0.0, 1.0); 
glMatrixMode(GL_PROJECTION); 
glLoadIdentity(); 
glFrustum(-1.0, 1.0, -1.0, 1.0, 1.0, 1000); 
glEnable(GL_CULL_FACE); 
glCullFace(GL_BACK); 


} 

void display() 
{ 
    glClear(GL_COLOR_BUFFER_BIT); 
glMatrixMode(GL_MODELVIEW); 
glLoadIdentity(); // reset the matrix 

gluLookAt(cam.pos.x, cam.pos.y, cam.pos.z, 
    cam.lookAt.x, cam.lookAt.y, cam.lookAt.z, 
    cam.up.x, cam.up.y, cam.up.z); // sets camera position. 

glColor3f(1.0, 0.0, 0.0); 
    glTranslatef(0.0f, 0.0f, -15.0f); 


for(int i = 0; i < 8; i++)//reads coords for verts from global arrays. 
{ 
    glBegin(GL_TRIANGLES); 
     int one = f[i][0].x; 
     int two = f[i][1].x; 
     int three = f[i][2].x; 

     glVertex3fv(&(v[one].x)); 
     glVertex3fv(&(v[two].x)); 
     glVertex3fv(&(v[three].x)); 
    glEnd(); 
} 


glFlush(); 
} 

void drawAxes() { 
glBegin(GL_LINES); 
    glVertex3f(0, 0, 0); 
    glVertex3f(10, 0, 0); 
    glVertex3f(0, 0, 0); 
    glVertex3f(0, 10, 0); 
    glVertex3f(0, 0, 0); 
    glVertex3f(0, 0, 10); 
glEnd();// draws a axis to show scene 
} 

void passiveMouseFunc(int x, int y) 
{ 
if (mouseDown == true) 
{ 
if (x > mousex) 
cam.lookAt.x+= 0.5; 
if (x < mousex) 
cam.lookAt.x-= 0.5; 
if (y > mousey) 
cam.lookAt.y-= 0.5; 
if (y < mousey) 
cam.lookAt.y+= 0.5; 


mousex = x; 
mousey = y; 
glutPostRedisplay(); 
} 
else 
{ 
if (x > mousex) 
cam.lookAt.x+= 0.0; 
if (x < mousex) 
cam.lookAt.x-= 0.0; 
if (y > mousey) 
cam.lookAt.y-= 0.0; 
if (y < mousey) 
cam.lookAt.y+= 0.0; 


mousex = x; 
mousey = y; 
glutPostRedisplay(); //redraws scene 

} 
} 
void glutMouseFunc(int button, int state, int x, int y) 
{ 
switch (button) 
{ 
case GLUT_LEFT_BUTTON: //makes it so i have to click to move cam 
    mouseDown = true; 
    break; 
case GLUT_RIGHT_BUTTON: 
    mouseDown = false; 
    break; 
} 
} 


void specialKeyboard(int key, int x, int y) // methods used for moving cam 
{ 
    switch (key) 
    { 
    case GLUT_KEY_RIGHT: 
    cam.pos.x+=0.2; 
    break; 
    case GLUT_KEY_LEFT: 
    cam.pos.x-=0.2; 
    break; 
    case GLUT_KEY_UP: 
    cam.pos.y+=0.2; 
    break; 
    case GLUT_KEY_DOWN: 
    cam.pos.y-=0.2; 
    break; 
    case GLUT_KEY_PAGE_UP: 
    cam.pos.z+=0.2; 
    break; 
    case GLUT_KEY_PAGE_DOWN: 
    cam.pos.z-=0.2; 
    break; 
} 

    glutPostRedisplay(); 

} 

void ObjloaderSpaceship() // loads a cube from .obj file 
{ 
int numVert = 0; 
int numNormals= 0; 
int numcoords = 0; 
int numFaces = 0; 
int ammount = 0; 
string test; 
ifstream inputFile; 
inputFile.open("cube.obj"); 

if (!inputFile.good()) 
    cout << "Problem with Input File"; 
else 
{ 
    while(!inputFile.eof()) 
    { 

     inputFile >> test; 

     if (test == "v") 
     { 
      inputFile >> v[numVert].x; 
      inputFile >> v[numVert].y; 
      inputFile >> v[numVert].z; 
      numVert++; 
     } 

     else if(test == "vn") 
     { 

      inputFile >> vn[numNormals].x; 
      inputFile >> vn[numNormals].y; 
      inputFile >> vn[numNormals].z; 
      numNormals++; 
     } 
     else if(test == "vt") 
     { 
      inputFile >> vt[numcoords].x; 
      inputFile >> vt[numcoords].y; 
      inputFile >> vt[numcoords].z; 
      numcoords++; 
     } 
     else if(test == "f") 
     { 


      string temp; 

      for(int count = 0; count < 3; count++) 
      { 

       inputFile >> temp; 
       stringstream stream(temp); 

       f[numFaces][count].x -= 1; 

       getline(stream, temp, '/'); 
       f[numFaces][count].x = atof(temp.c_str()); 
       getline(stream, temp, '/'); 
       f[numFaces][count].y = atof(temp.c_str()); 
       getline(stream, temp, '/'); 
       f[numFaces][count].z = atof(temp.c_str()); 
      } 

      numFaces++; 
     } 


    } 


} 
} 

//void normalKeyboard(unsigned char key, int x, int y) { 
// switch (key) 
// { 

// case 'w' : 
//  cam.lookAt.y+=0.5; 
//  break; 
// case 'a' : 
//  cam.lookAt.y-=0.5; 
//  break; 
// case 's' : 
//  cam.lookAt.x-=0.5; 
//  break; 
// case 'd' : 
//  cam.lookAt.x+=0.5; 
//  break; 
// } 
    // 
// glutPostRedisplay(); 

//} 




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

    glutInit(&argc, argv); 
    glutCreateWindow("C++ Assignment"); 
    drawAxes(); 
    glutMouseFunc(glutMouseFunc); 
    glutPassiveMotionFunc(passiveMouseFunc); 
    ObjloaderSpaceship(); 
    glutDisplayFunc(display); 
    glutSpecialFunc(specialKeyboard); 
// glutKeyboardFunc(normalKeyboard); 

    init(); 
    glutMainLoop(); 


} 

，這裏是obj的文件。

# 3ds Max Wavefront OBJ Exporter v0.97b - (c)2007 guruware 
# File Created: 23.04.2013 13:50:59 

mtllib cube.mtl 

# 
# object Box001 
# 

v 2.2289 0.0000 -1.5936 
v 2.2289 0.0000 -30.3830 
v 31.1072 0.0000 -30.3830 
v 31.1072 0.0000 -1.5936 
v 2.2289 29.4346 -1.5936 
v 31.1072 29.4346 -1.5936 
v 31.1072 29.4346 -30.3830 
v 2.2289 29.4346 -30.3830 
# 8 vertices 

vn 0.0000 -1.0000 -0.0000 
vn 0.0000 1.0000 -0.0000 
vn 0.0000 0.0000 1.0000 
vn 1.0000 0.0000 -0.0000 
vn 0.0000 0.0000 -1.0000 
vn -1.0000 0.0000 -0.0000 
# 6 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 

g Box001 
usemtl wire_006135006 
f 1/1/1 2/2/1 3/3/1 
f 3/3/1 4/4/1 1/1/1 
f 5/4/2 6/1/2 7/2/2 
f 7/2/2 8/3/2 5/4/2 
f 1/4/3 4/1/3 6/2/3 
f 6/2/3 5/3/3 1/4/3 
f 4/4/4 3/1/4 7/2/4 
f 7/2/4 6/3/4 4/4/4 
f 3/4/5 2/1/5 8/2/5 
f 8/2/5 7/3/5 3/4/5 
f 2/4/6 1/1/6 5/2/6 
f 5/2/6 8/3/6 2/4/6 
# 12 faces 

Answer 1

這段代碼很粗糙，並且有很多基於輸入數據假設的缺陷。但這是你需要解決的問題，而不是問題的一部分。

您可能錯過的信息的重要一點是OBJ格式指定了基於1的索引的任何內容。但在C/C++中，索引是基於0的。您可以在閱讀例程或渲染例程中修復它。 （我會去閱讀，因爲它使您能夠閱讀其他格式並不會改變渲染代碼。）

因此，在管線219更改代碼是：

else if(test == "f") 
    { 
     string temp; 
     for(int count = 0; count < 3; count++) 
     { 
      inputFile >> temp; 
      stringstream stream(temp); 

      getline(stream, temp, '/'); 
      f[numFaces][count].x = atoi(temp.c_str()) - 1; 
      getline(stream, temp, '/'); 
      f[numFaces][count].y = atoi(temp.c_str()) - 1; 
      getline(stream, temp, '/'); 
      f[numFaces][count].z = atoi(temp.c_str()) - 1; 
     } 

     numFaces++; 
    } 

也絕對想要改變你的臉部格式爲整數，而不是浮動。我完全可以想象這些值會漂移。

還需要捕獲其中的情況：

• 只有一個頂點（1）
• 頂點和紋理線（1/1）
• 頂點和正常（1 // 1）
• 面對的是不是一個三角形（超過3個頂點）