SDL OpenGL 纹理显示问题

Question

我正在关注this tutorial，以便从 SDL_Surface 加载 OpenGL 纹理，我复制/粘贴代码并对其进行了调整，但它只显示缓冲区的错误旧部分，即有点烦人......因为我不知道出了什么问题。我还在 Mac Os X 上使用 Qt5。这是我的代码

GLuint texture;         // This is a handle to our texture object
SDL_Surface *surface;   // This surface will tell us the details of the image
GLenum texture_format;
GLint  nOfColors;
surface = IMG_Load("/brique.png");

if ( surface ) {

    // get the number of channels in the SDL surface
    nOfColors = surface->format->BytesPerPixel;
    if (nOfColors == 4)     // contains an alpha channel
    {
        if (surface->format->Rmask == 0x000000ff)
            texture_format = GL_RGBA;
        else
            texture_format = GL_BGRA;
    } else if (nOfColors == 3)     // no alpha channel
    {
        if (surface->format->Rmask == 0x000000ff)
            texture_format = GL_RGB;
        else
            texture_format = GL_BGR;
    } else {
        printf("warning: the image is not truecolor..  this will probably break\n");
        // this error should not go unhandled
    }

    glEnable( GL_TEXTURE_2D );
    // Have OpenGL generate a texture object handle for us
    glGenTextures( 1, &texture );

    // Bind the texture object
    glBindTexture( GL_TEXTURE_2D, texture );

    // Set the texture's stretching properties
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

    // Edit the texture object's image data using the information SDL_Surface gives us
    glTexImage2D( GL_TEXTURE_2D, 0, nOfColors, surface->w, surface->h, 0, texture_format, GL_UNSIGNED_BYTE, surface->pixels );
}
else {
    printf("SDL could not load image.bmp: %s\n", SDL_GetError());
    SDL_Quit();
    exit (1);
}

// Free the SDL_Surface only if it was successfully created
if ( surface ) {
    SDL_FreeSurface( surface );
}

结果如下：

这是来自函数 glTexImage2D 的调试

Answer 1

您可能或没有声明 a（这会翻转 屏幕缓冲区）

SDL_GL_SwapBuffers();

这样做把它放在循环的最后部分：

qglClearColor(qtPurple.dark());

/****************************************
... some ogl initialization code here ...
****************************************/

while (!done)
{
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   /***********************************
   ... some ogl rendering code here ...
   ***********************************/

   SDL_GL_SwapBuffers();
}

在 QT5 OGL 上查看本教程：

• http://qt-project.org/doc/qt-5.0/qtopengl/hellogl.html