OpenGL显示白色纹理

Question

我在使用OpenGL和C ++显示纹理时遇到麻烦。 我正在从RGB Raw文件加载纹理，并将其绑定到纹理，但是当我尝试在四边形上显示纹理时，纹理为白色。 我正在使用glGetError，它不会捕获任何错误。 这是我的代码：

#include <iostream>
#include <windows.h>       // Standard header for MS Windows applications
#include <GL/gl.h>         // Open Graphics Library (OpenGL) header
#include <GL/glut.h>       // The GL Utility Toolkit (GLUT) Header
using namespace std;

typedef struct {
    int width;
    int height;
    char* title;
    float field_of_view_angle;
    float z_near;
    float z_far;
} glutWindow;
glutWindow win;
float rotation, distance1;
bool light=TRUE;
bool trans=FALSE;
GLuint tex;

void drawFlatFace(float size)
{
    glBegin(GL_QUADS);
        glTexCoord2f (0, 0);
        glVertex3f(-size, -2*size, size);
        glTexCoord2f (1.0, 0);
        glVertex3f(size, -2*size, size);
        glTexCoord2f (1.0, 1.0);
        glVertex3f(size, 2*size, size);
        glTexCoord2f (0, 1.0);
        glVertex3f(-size, 2*size, size);
    glEnd();
}

void drawBlock(float size){
    glColor3f(1.0f,1.0f,1.0f);
    glPushMatrix();
        drawFlatFace (size);
        glRotatef (90, 0, 1, 0);
        drawFlatFace (size);
        glRotatef (90, 0, 1, 0);
        drawFlatFace (size);
        glRotatef (90, 0, 1, 0);
        drawFlatFace (size);
    glPopMatrix();
}

GLuint loadTexture(const char * filename) {
    GLuint text[1];
    GLubyte* bits = new GLubyte[512*256*3];
    FILE *file;
    fopen_s(&file,filename,"rb");
    fread(&bits,(512*256*3),1,file);
    fclose(file);
    glGenTextures(1,&text[0]); 
    glBindTexture(GL_TEXTURE_2D,text[0]);
    glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_MODULATE);
    glTexImage2D(GL_TEXTURE_2D, 0, 3,256,512,0,GL_RGB,GL_UNSIGNED_BYTE,bits);
    free(bits);
    return text[0];
}

void display() 
{
    GLenum err;
    err = glGetError();
    if (err != GL_NO_ERROR)
    {
        cerr << "OpenGL error: " << gluErrorString(err) << endl;
    }

    tex=loadTexture("tex.raw");
    glBindTexture(GL_TEXTURE_2D,tex);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);          // Clear Screen and Depth Buffer
    glLoadIdentity();
    gluLookAt( 10+distance1 ,1.4,0, 0,0,0, 0,1,0);                    // Define a viewing transformation
    glRotatef(rotation, 0.f, 1.f, 0.f);
    drawBlock(3);
    if (light)  glEnable(GL_LIGHTING);      // Enable Lighting
    else glDisable(GL_LIGHTING);      // Disable Lighting
    if (trans) glEnable (GL_BLEND);  // Enable Transparency
    else glDisable(GL_BLEND);      // Disable Transparency
    glutSwapBuffers();
}


void initialize () 
{
    glMatrixMode(GL_PROJECTION);                                                // select projection matrix
    glViewport(0, 0, win.width, win.height);                                    // set the viewport
    glLoadIdentity();                                                           // reset projection matrix
    GLfloat aspect = (GLfloat) win.width / win.height;
    gluPerspective(win.field_of_view_angle, aspect, win.z_near, win.z_far);     // set up a perspective projection matrix
    glMatrixMode(GL_MODELVIEW);                                                 // specify which matrix is the current matrix
    glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );                        // specify implementation-specific hints
    GLfloat amb_light[] = { 0.3, 0.3, 0.3, 1.0 };
    GLfloat diffuse[] = { 0.4, 0.4, 0.4, 1.0 };
    GLfloat specular[] = { 0.5, 0.5, 0.5, 1.0 };
    glLightModelfv( GL_LIGHT_MODEL_AMBIENT, amb_light );
    glLightfv( GL_LIGHT0, GL_SPECULAR, specular );
    glLightfv( GL_LIGHT0, GL_DIFFUSE, diffuse );
    GLfloat light_position[] = { 1.0, 1.0, 0, 0.0 };
    glLightfv(GL_LIGHT0, GL_POSITION, light_position);
    glEnable( GL_LIGHT0 );
    glEnable( GL_COLOR_MATERIAL );
    glEnable( GL_LIGHTING );
    //glLightModeli( GL_LIGHT_MODEL_TWO_SIDE, GL_FALSE );

    glEnable(GL_TEXTURE_2D);                        // Enable Texture Mapping
    glShadeModel(GL_SMOOTH);                        // Enable Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);                   // Black Background
    glClearDepth(1.0f);                         // Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);                        // Enables Depth Testing
    glDepthFunc(GL_LEQUAL);                         // The Type Of Depth Testing To Do
    glTexParameteri( GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR);
}


void keyboard ( int key, int mousePositionX, int mousePositionY )       
{ 
    switch ( key ) 
  {

    case GLUT_KEY_DOWN:
        if (distance1<9){
        distance1=distance1+.3;
        }
        break;      

    case GLUT_KEY_UP:
        if (distance1>-9){
        distance1=distance1-.3;
        }
        break;      

    case GLUT_KEY_LEFT:
        rotation=rotation-2;
        break;      

    case GLUT_KEY_RIGHT:
        rotation=rotation+2;
        break; 

    case GLUT_KEY_PAGE_UP:
        light=TRUE;
        break; 

    case GLUT_KEY_PAGE_DOWN:
        light=FALSE;
        break; 

    case GLUT_KEY_HOME:
        trans=TRUE;
        break; 

    case GLUT_KEY_END:
        trans=FALSE;
        break; 


    default:      
      break;
  }
}

int main(int argc, char **argv) 
{
    // set window values
    win.width = 800;
    win.height = 600;
    win.title = "Test Texture";
    win.field_of_view_angle = 45;
    win.z_near = 1.0f;
    win.z_far = 500.0f;

    // initialize and run program
    glutInit(&argc, argv);                                      // GLUT initialization
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );  // Display Mode
    glutInitWindowSize(win.width,win.height);                   // set window size
    glutCreateWindow(win.title);                                // create Window
    // Callback functions
    glutDisplayFunc(display);                                   // register Display Function
    glutIdleFunc( display );                                    // register Idle Function
    glutSpecialFunc( keyboard );                                // register Keyboard Handler
    initialize();
    glutMainLoop();                                             // run GLUT mainloop
    return 0;
}

我想补充一点，在IrfanView中加载256x512、24BPP，RGB时，原始文件可以正确显示（大小为393,216字节或3 * 512 * 256）

Answer 1

这行：

glTexParameteri( GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR);

不应在您的主初始化中使用，而应在设置纹理本身时（即在绑定之后）进行。

通常，您可能还需要设置MAG_FILTER和纹理坐标环绕模式。

此外，您似乎在每次渲染时都在加载纹理。 否则，性能将很糟糕，并且由于GL将继续分配新的纹理，您将耗尽内存。