glext.h Windows 和 Mac

Question

我正在尝试通过 qt-project 提供的教程学习 OpenGL 和 Qt。我需要编写一个可以在 Windows 和 Mac 上运行的应用程序。但是我可能对他们给出的示例有疑问：在使用 glext.h 库时，他们指定 OS 是 windows（WIN32 的东西）。现在我不确定他们的例子是否可以运行 on Mac。他们甚至在教程中说：

"glActiveTexture() and GL_TEXTUREi can then be used on Windows."

这是他们的代码：

#include "glwidget.h"
#include <QMouseEvent>
#include <QWheelEvent>

//! [0]
#ifdef WIN32
    #include <GL/glext.h>
    PFNGLACTIVETEXTUREPROC pGlActiveTexture = NULL;
    #define glActiveTexture pGlActiveTexture
#endif //WIN32
//! [0]

GlWidget::GlWidget(QWidget *parent)
    : QGLWidget(QGLFormat(/* Additional format options */), parent)
{
    alpha = 25;
    beta = -25;
    distance = 2.5;
}

GlWidget::~GlWidget()
{
}

QSize GlWidget::sizeHint() const
{
    return QSize(640, 480);
}

//! [1]
void GlWidget::initializeGL()
{
    //! [1]
    //! [2]
    #ifdef WIN32
        glActiveTexture = (PFNGLACTIVETEXTUREPROC) wglGetProcAddress((LPCSTR) "glActiveTexture");
    #endif
    //! [2]

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    qglClearColor(QColor(Qt::black));

    shaderProgram.addShaderFromSourceFile(QGLShader::Vertex, ":/vertexShader.vsh");
    shaderProgram.addShaderFromSourceFile(QGLShader::Fragment, ":/fragmentShader.fsh");
    shaderProgram.link();

    vertices << QVector3D(-0.5, -0.5,  0.5) << QVector3D( 0.5, -0.5,  0.5) << QVector3D( 0.5,  0.5,  0.5) // Front
             << QVector3D( 0.5,  0.5,  0.5) << QVector3D(-0.5,  0.5,  0.5) << QVector3D(-0.5, -0.5,  0.5)
             << QVector3D( 0.5, -0.5, -0.5) << QVector3D(-0.5, -0.5, -0.5) << QVector3D(-0.5,  0.5, -0.5) // Back
             << QVector3D(-0.5,  0.5, -0.5) << QVector3D( 0.5,  0.5, -0.5) << QVector3D( 0.5, -0.5, -0.5)
             << QVector3D(-0.5, -0.5, -0.5) << QVector3D(-0.5, -0.5,  0.5) << QVector3D(-0.5,  0.5,  0.5) // Left
             << QVector3D(-0.5,  0.5,  0.5) << QVector3D(-0.5,  0.5, -0.5) << QVector3D(-0.5, -0.5, -0.5)
             << QVector3D( 0.5, -0.5,  0.5) << QVector3D( 0.5, -0.5, -0.5) << QVector3D( 0.5,  0.5, -0.5) // Right
             << QVector3D( 0.5,  0.5, -0.5) << QVector3D( 0.5,  0.5,  0.5) << QVector3D( 0.5, -0.5,  0.5)
             << QVector3D(-0.5,  0.5,  0.5) << QVector3D( 0.5,  0.5,  0.5) << QVector3D( 0.5,  0.5, -0.5) // Top
             << QVector3D( 0.5,  0.5, -0.5) << QVector3D(-0.5,  0.5, -0.5) << QVector3D(-0.5,  0.5,  0.5)
             << QVector3D(-0.5, -0.5, -0.5) << QVector3D( 0.5, -0.5, -0.5) << QVector3D( 0.5, -0.5,  0.5) // Bottom
             << QVector3D( 0.5, -0.5,  0.5) << QVector3D(-0.5, -0.5,  0.5) << QVector3D(-0.5, -0.5, -0.5);
    //! [3]
    textureCoordinates << QVector2D(0, 0) << QVector2D(.5, 0) << QVector2D(.5, .5) // Front
                       << QVector2D(.5, .5) << QVector2D(0, .5) << QVector2D(0, 0)
                       << QVector2D(0, 0) << QVector2D(1, 0) << QVector2D(1, 1) // Back
                       << QVector2D(1, 1) << QVector2D(0, 1) << QVector2D(0, 0)
                       << QVector2D(0, 0) << QVector2D(1, 0) << QVector2D(1, 1) // Left
                       << QVector2D(1, 1) << QVector2D(0, 1) << QVector2D(0, 0)
                       << QVector2D(0, 0) << QVector2D(1, 0) << QVector2D(1, 1) // Right
                       << QVector2D(1, 1) << QVector2D(0, 1) << QVector2D(0, 0)
                       << QVector2D(0, 0) << QVector2D(1, 0) << QVector2D(1, 1) // Top
                       << QVector2D(1, 1) << QVector2D(0, 1) << QVector2D(0, 0)
                       << QVector2D(0, 0) << QVector2D(1, 0) << QVector2D(1, 1) // Bottom
                       << QVector2D(1, 1) << QVector2D(0, 1) << QVector2D(0, 0);

    texture = bindTexture(QPixmap(":/texture.png"));
    //! [3]
    //! [4]
}
//! [4]

void GlWidget::resizeGL(int width, int height)
{
   if (height == 0) {
        height = 1;
    }

    pMatrix.setToIdentity();
    pMatrix.perspective(60.0, (float) width / (float) height, 0.001, 1000);

    glViewport(0, 0, width, height);
}

//! [5]
void GlWidget::paintGL()
{
    //! [5]
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    QMatrix4x4 mMatrix;
    QMatrix4x4 vMatrix;

    QMatrix4x4 cameraTransformation;
    cameraTransformation.rotate(alpha, 0, 1, 0);
    cameraTransformation.rotate(beta, 1, 0, 0);

    QVector3D cameraPosition = cameraTransformation * QVector3D(0, 0, distance);
    QVector3D cameraUpDirection = cameraTransformation * QVector3D(0, 1, 0);

    vMatrix.lookAt(cameraPosition, QVector3D(0, 0, 0), cameraUpDirection);

    //! [6]
    shaderProgram.bind();

    shaderProgram.setUniformValue("mvpMatrix", pMatrix * vMatrix * mMatrix);

    shaderProgram.setUniformValue("texture", 0);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texture);
    glActiveTexture(0);

    shaderProgram.setAttributeArray("vertex", vertices.constData());
    shaderProgram.enableAttributeArray("vertex");

    shaderProgram.setAttributeArray("textureCoordinate", textureCoordinates.constData());
    shaderProgram.enableAttributeArray("textureCoordinate");

    glDrawArrays(GL_TRIANGLES, 0, vertices.size());

    shaderProgram.disableAttributeArray("vertex");

    shaderProgram.disableAttributeArray("textureCoordinate");

    shaderProgram.release();
}
//! [6]

void GlWidget::mousePressEvent(QMouseEvent *event)
{
    lastMousePosition = event->pos();

    event->accept();
}

void GlWidget::mouseMoveEvent(QMouseEvent *event)
{
    int deltaX = event->x() - lastMousePosition.x();
    int deltaY = event->y() - lastMousePosition.y();

    if (event->buttons() & Qt::LeftButton) {
        alpha -= deltaX;
        while (alpha < 0) {
            alpha += 360;
        }
        while (alpha >= 360) {
            alpha -= 360;
        }

        beta -= deltaY;
        if (beta < -90) {
            beta = -90;
        }
        if (beta > 90) {
            beta = 90;
        }

        updateGL();
    }

    lastMousePosition = event->pos();

    event->accept();
}

void GlWidget::wheelEvent(QWheelEvent *event)
{
    int delta = event->delta();

    if (event->orientation() == Qt::Vertical) {
        if (delta < 0) {
            distance *= 1.1;
        } else if (delta > 0) {
            distance *= 0.9;
        }

        updateGL();
    }

    event->accept();
}

那么运行在 Mac 上可以吗？如果不能，我应该更改什么？

Answer 1

在 MacOS X 上您不需要 glext.h，因为可用的（最大）OpenGL 版本由 OS 版本决定。所以当用例如编译时Yosemite SDK 它已经涵盖了 OpenGL-4。

Windows不一样。唯一声称受支持的 OpenGL 版本是 Windows Vista 之前的 OpenGL-1.1 和 Vista 之后的 OpenGL-1.4；所有 Windows 版本唯一支持的 ABI 是 OpenGL-1.1。所以你必须使用扩展机制来获得更多的功能。

*nix 系统相似，不同之处在于共同的基线是 OpenGL-1.2

glext.h Windows 和 Mac

glext.h for Windows and Mac

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