如何在 beginNativePainting() 中翻转纹理？

发布于 2024-12-28 11:38:05 字数 1134 浏览 0 评论 0原文

我正在编写一个继承自QGLWidget的类：

class GLWidget : public QGLWidget
{
    Q_OBJECT

public:
    GLWidget(QWidget *parent = 0);
    ~GLWidget();

    void paintEvent(QPaintEvent *event);    

private:
    QImage* _frame;
};

GLWidget的构造函数从磁盘加载图像，paintEvent()负责使用在 beginNativePainting() 和 endNativePainting() 之间执行的本机 OpenGL 调用将数据发送到 GPU，并且工作正常。

问题是图像显示翻转（垂直），我需要解决这个问题。我还没有找到解决这个问题的方法，所以我希望有人可以帮助我解决这个问题。

在本机 Glut 应用程序中，我可以像这样简单地调用 glFrustum() 来进行翻转：

static void Reshape( int width, int height )
{
   glViewport( 0, 0, width, height );

   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();

   glFrustum( -1.0, 1.0, 1.0, -1.0, 10.0, 100.0 );  // flip vertically

   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -15.0 );
}

但我尝试在 beginNativePainting() 之后加载投影矩阵并调用 < code>glFrustum() 与上面的调用具有相同的值，我得到的只是黑屏（这意味着它没有按预期工作）。

有什么建议吗？

另外，使用QImage的mirrowed(false, true)方法进行翻转对图像的显示没有任何影响。

原文

I'm writing a class that inherits from QGLWidget:

class GLWidget : public QGLWidget
{
    Q_OBJECT

public:
    GLWidget(QWidget *parent = 0);
    ~GLWidget();

    void paintEvent(QPaintEvent *event);    

private:
    QImage* _frame;
};

The constructor of GLWidget loads an image from the disk, and paintEvent() is responsible to send the data to the GPU using native OpenGL calls that are executed between beginNativePainting() and endNativePainting(), and this works OK.

The problem is that the image is being displayed flipped (vertically), and I need to fix this. I haven't found a way to this so I'm hoping somebody can help me on this issue.

In a native Glut application I could simply call glFrustum() like this to do the flip:

static void Reshape( int width, int height )
{
   glViewport( 0, 0, width, height );

   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();

   glFrustum( -1.0, 1.0, 1.0, -1.0, 10.0, 100.0 );  // flip vertically

   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -15.0 );
}

But I've tried loading the projection matrix after the beginNativePainting() and calling glFrustum() with the same values as the call above and all I get is a black screen (which means it didn't worked as expected).

Any tips?

Also, using the mirrowed(false, true) method of QImage to do the flipping didn't had any effect in the displaying of the image.

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