纹理在缩放而不是在Qt中重复

Question

I just started working on opengl in qt, using texture i am displaying image in quard.

then i set gltexture wrap mode to gl_repeat but its not repeating.

I tried even gl_clamp_to_edge still its not working.

images size 256*256

code:

GLuint _textureId; //The id of the texture
int _wdth;
int _hight;
void LoadGLTextures( const char * name )
{
    QImage img;

    if(!img.load(name)){
        qDebug() << "ERROR in loading image";
    }

    QImage t = QGLWidget::convertToGLFormat(img);

    _wdth = t.width();
    _hight = t.height();
    qDebug()<<"width = "<<_wdth<<"height ="<<_hight;
    glGenTextures(1, &_textureId);
    glBindTexture(GL_TEXTURE_2D, _textureId);
    glTexImage2D(GL_TEXTURE_2D, 0, 3, t.width(), t.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, t.bits());

    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
}

void GLWin::initializeGL()
{
    qglColor(Qt::black);
    glEnable(GL_CULL_FACE);
    glShadeModel(GL_SMOOTH);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_MULTISAMPLE);
    static GLfloat lightPosition[4] = { 0.5, 5.0, 7.0, 1.0 };
    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
    ///cameraPos = 0;
    glEnable(GL_TEXTURE_2D);
    LoadGLTextures("resources/Green_Dragon.jpeg");
}
void GLWin::paintGL()
{
       glClearColor( 0.0f, 0.0f, 0.0f, 0.0f);
       glClear( GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT );

       glMatrixMode( GL_MODELVIEW );
       glLoadIdentity();

       glEnable(GL_TEXTURE_2D);
       glColor3f(0.5, 0.5, 0);
       glBindTexture(GL_TEXTURE_2D, _textureId);

       glBegin(GL_QUADS);
       glTexCoord2f(0.0f, 0.0f); glVertex2f(-0.5f, -0.5f);  // vertex 1
       glTexCoord2f(1.0f, 0.0f); glVertex2f(0.5f, -0.5f); // vertex 2
       glTexCoord2f(1.0f, 1.0f); glVertex2f(0.5f, 0.5f); // vertex 3
       glTexCoord2f(0.0f, 1.0f); glVertex2f(-0.5f, 0.5f); // vertex 4
       glEnd();
       glDisable(GL_TEXTURE_2D);
       glFlush();
}
void GLWin::resizeGL(int width, int height)
{
    glViewport(0, 0, (GLint)width, (GLint)height);
    glMatrixMode(GL_PROJECTION);  // To operate on the Projection matrix
    glLoadIdentity();
    glOrtho(-0.5, 0.5, -0.5, 0.5, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

Answer 1

   glTexCoord2f(0.0f, 0.0f); glVertex2f(-0.5f, -0.5f);  // vertex 1
   glTexCoord2f(1.0f, 0.0f); glVertex2f(0.5f, -0.5f); // vertex 2
   glTexCoord2f(1.0f, 1.0f); glVertex2f(0.5f, 0.5f); // vertex 3
   glTexCoord2f(0.0f, 1.0f); glVertex2f(-0.5f, 0.5f); // vertex 4

If those are your texture coordinates, then it's not going to repeat. Texture wrap modes only apply when the texture coordinate exceeds the [0, 1] range. Since your texture coordinates are within that range, no repeating will happen.

You see scaling of the texture because you are scaling the positions of the triangles. And therefore, the texture will be mapped in accord with those scaled positions.

You could use the texture matrix to do some transformations on the texture coordinates if you want to scale them.