【小沐学QT】QT学习之OpenGL开发笔记

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文章目录

1、简介2、Qt + QOpenGLWidget + gl函数3、Qt + QOpenGLWidget + qt函数4、Qt + QOpenGLWindow5、Qt + glut6、Qt + glfw结语

1、简介

Qt提供了与OpenGL实现集成的支持，使开发人员有机会在更传统的用户界面的同时显示硬件加速的3D图形。

Qt有两种主要的UI开发方法：QtQuick和QtWidgets。它们的存在是为了支持不同类型的用户界面，并建立在针对每种类型进行了优化的独立图形引擎上。

可以将在OpenGL图形API中编写的代码与Qt中的这两种用户界面类型结合起来。当应用程序有自己的OpenGL相关代码时，或者当它与基于OpenGL的第三方渲染器集成时，这可能很有用。

Qt OpenGL模块包含方便类，使这种类型的集成更容易、更快。

QOpenGLWidget提供了三个方便的虚拟函数，您可以在子类中重新实现这些函数来执行典型的OpenGL任务：

paintGL（）-渲染OpenGL场景。每当需要更新小部件时调用。resizeGL（）-设置OpenGL视口、投影等。每当小部件被调整大小时（以及当它第一次显示时，因为所有新创建的小部件都会自动获得调整大小事件），都会调用它。initializeGL（）-设置OpenGL资源和状态。在第一次调用resizeGL（）或paintGL（）之前调用一次。

最简单的QOpenGLWidget子类可能如下所示：

class MyGLWidget : public QOpenGLWidget{public:    MyGLWidget(QWidget *parent) : QOpenGLWidget(parent) { }protected:    void initializeGL() override    {        // Set up the rendering context, load shaders and other resources, etc.:        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();        f->glClearColor(1.0f, 1.0f, 1.0f, 1.0f);        ...    }    void resizeGL(int w, int h) override    {        // Update projection matrix and other size related settings:        m_projection.setToIdentity();        m_projection.perspective(45.0f, w / float(h), 0.01f, 100.0f);        ...    }    void paintGL() override    {        // Draw the scene:        QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();        f->glClear(GL_COLOR_BUFFER_BIT);        ...    }};

或者，可以通过从QOpenGLFunctions派生来避免每个OpenGL调用的前缀：

class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions{    ...    void initializeGL() override    {        initializeOpenGLFunctions();        glClearColor(...);        ...    }    ...};

2、Qt + QOpenGLWidget + gl函数

untitled4.pro

QT       += core guigreaterThan(QT_MAJOR_VERSION, 4): QT += widgetsCONFIG += c++11DEFINES += QT_DEPRECATED_WARNINGSSOURCES += \    main.cpp \    qopenglwidgettest.cppHEADERS += \    qopenglwidgettest.hFORMS += \    qopenglwidgettest.ui# Default rules for deployment.qnx: target.path = /tmp/$${TARGET}/binelse: unix:!android: target.path = /opt/$${TARGET}/bin!isEmpty(target.path): INSTALLS += targetRESOURCES += \    res.qrc

main.cpp

#include "qopenglwidgettest.h"#include <QApplication>int main(int argc, char *argv[]){    QApplication a(argc, argv);    QOpenGLWidgetTest w;    w.show();    return a.exec();}

qopenglwidgettest.h

#ifndef QOPENGLWIDGETTEST_H#define QOPENGLWIDGETTEST_H#include <QOpenGLWidget>#include <QOpenGLFunctions_3_3_Core>#include <QOpenGLShaderProgram>QT_BEGIN_NAMESPACEnamespace Ui { class QOpenGLWidgetTest; }QT_END_NAMESPACEclass QOpenGLWidgetTest : public QOpenGLWidget        , protected /*QOpenGLExtraFunctions*/QOpenGLFunctions_3_3_Core{    Q_OBJECTpublic:    QOpenGLWidgetTest(QWidget *parent = nullptr);    ~QOpenGLWidgetTest();protected:    virtual void initializeGL();    virtual void resizeGL(int w, int h);    virtual void paintGL();private:    Ui::QOpenGLWidgetTest *ui;    QOpenGLShaderProgram shaderProgram;};#endif // QOPENGLWIDGETTEST_H

qopenglwidgettest.cpp

#include "qopenglwidgettest.h"#include "ui_qopenglwidgettest.h"static GLuint VBO, VAO, EBO;QOpenGLWidgetTest::QOpenGLWidgetTest(QWidget *parent)    : QOpenGLWidget(parent)    , ui(new Ui::QOpenGLWidgetTest){    ui->setupUi(this);}QOpenGLWidgetTest::~QOpenGLWidgetTest(){    delete ui;    glDeleteVertexArrays(1, &VAO);    glDeleteBuffers(1, &VBO);    glDeleteBuffers(1, &EBO);}void QOpenGLWidgetTest::initializeGL(){    this->initializeOpenGLFunctions();    bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/new/prefix1/triangle.vert");    if (!success) {        qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();        return;    }    success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/new/prefix1/triangle.frag");    if (!success) {        qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();        return;    }    success = shaderProgram.link();    if(!success) {        qDebug() << "shaderProgram link failed!" << shaderProgram.log();    }    //VAO，VBO数据部分    float vertices[] = {        0.5f,  0.5f, 0.0f,  // top right         0.5f, -0.5f, 0.0f,  // bottom right        -0.5f, -0.5f, 0.0f,  // bottom left        -0.5f,  0.5f, 0.0f   // top left    };    unsigned int indices[] = {  // note that we start from 0!        0, 1, 3,  // first Triangle        1, 2, 3   // second Triangle    };    glGenVertexArrays(1, &VAO);    glGenBuffers(1, &VBO);    glGenBuffers(1, &EBO);    // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).    glBindVertexArray(VAO);    glBindBuffer(GL_ARRAY_BUFFER, VBO);    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);  //顶点数据复制到缓冲    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (void*)0);//告诉程序如何解析顶点数据    glEnableVertexAttribArray(0);    glBindBuffer(GL_ARRAY_BUFFER, 0);//取消VBO的绑定, glVertexAttribPointer已经把顶点属性关联到顶点缓冲对象了//    remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.//    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);//    You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other//    VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.    glBindVertexArray(0);   //取消VAO绑定}void QOpenGLWidgetTest::resizeGL(int w, int h){    glViewport(0, 0, w, h);}void QOpenGLWidgetTest::paintGL(){    glClearColor(0.5f, 0.5f, 0.5f, 1.0f);    glClear(GL_COLOR_BUFFER_BIT);    shaderProgram.bind();        glBindVertexArray(VAO); //    glDrawArrays(GL_TRIANGLES, 0, 6);    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);    shaderProgram.release();}

triangle.vert

#version 330 corelayout(location = 0) in vec3 aPos;void main(){    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0f);}

triangle.frag

#version 330 coreout vec4 FragColor;void main(){    FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);}

运行如下：

3、Qt + QOpenGLWidget + qt函数

qtfunctionwidget.h

#ifndef QTFUNCTIONWIDGET_H#define QTFUNCTIONWIDGET_H#include <QOpenGLWidget>#include <QOpenGLShader>#include <QOpenGLShaderProgram>#include <QDebug>#include <QOpenGLFunctions>#include <QOpenGLVertexArrayObject>#include <QOpenGLBuffer>class QtFunctionWidget : public QOpenGLWidget, protected QOpenGLFunctions{public:    QtFunctionWidget(QWidget *parent = nullptr);    ~QtFunctionWidget() Q_DECL_OVERRIDE;protected:    virtual void initializeGL() Q_DECL_OVERRIDE;    virtual void resizeGL(int w, int h) Q_DECL_OVERRIDE;    virtual void paintGL() Q_DECL_OVERRIDE;private:    QOpenGLShaderProgram shaderProgram;    QOpenGLBuffer vbo, ebo;    QOpenGLVertexArrayObject vao;};#endif // QTFUNCTIONWIDGET_H

qtfunctionwidget.cpp

#include "QtFunctionWidget.h"#include <QFile>QtFunctionWidget::QtFunctionWidget(QWidget *parent) : QOpenGLWidget (parent),    vbo(QOpenGLBuffer::VertexBuffer),    ebo(QOpenGLBuffer::IndexBuffer){}QtFunctionWidget::~QtFunctionWidget(){    makeCurrent();    vbo.destroy();    ebo.destroy();    vao.destroy();    doneCurrent();}void QtFunctionWidget::initializeGL(){    this->initializeOpenGLFunctions();    bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/new/prefix1/triangle.vert");    if (!success) {        qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();        return;    }    success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/new/prefix1/triangle.frag");    if (!success) {        qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();        return;    }    success = shaderProgram.link();    if(!success) {        qDebug() << "shaderProgram link failed!" << shaderProgram.log();    }    //VAO，VBO数据部分    GLfloat vertices[] = {        0.7f,  0.5f, 0.0f,  // top right         0.5f, -0.6f, 0.0f,  // bottom right        -0.6f, -0.5f, 0.0f,  // bottom left        -0.5f,  0.7f, 0.0f   // top left    };    unsigned int indices[] = {  // note that we start from 0!        0, 1, 3,  // first Triangle        1, 2, 3   // second Triangle    };    QOpenGLVertexArrayObject::Binder vaoBind(&vao);    vbo.create();    vbo.bind();    vbo.allocate(vertices, sizeof(vertices));    ebo.create();    ebo.bind();    ebo.allocate(indices, sizeof(indices));    int attr = -1;    attr = shaderProgram.attributeLocation("aPos");    shaderProgram.setAttributeBuffer(attr, GL_FLOAT, 0, 3, sizeof(GLfloat) * 3);    shaderProgram.enableAttributeArray(attr);    vbo.release();//    remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.//    ebo.release();}void QtFunctionWidget::resizeGL(int w, int h){    glViewport(0, 0, w, h);}void QtFunctionWidget::paintGL(){    glClearColor(0.2f, 0.2f, 0.0f, 1.0f);    glClear(GL_COLOR_BUFFER_BIT);    shaderProgram.bind();    {        QOpenGLVertexArrayObject::Binder vaoBind(&vao);        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);    }    shaderProgram.release();}

4、Qt + QOpenGLWindow

untitled4.pro

QT       += core guigreaterThan(QT_MAJOR_VERSION, 4): QT += widgetsTARGET = OpenGLTEMPLATE = appCONFIG += c++11SOURCES += \    main.cpp \    mywindow.cppHEADERS += \    mywindow.hLIBS += -lopengl32\        -lglu32

main.cpp

#include <QApplication>#include <MyWindow.h>int main(int argc, char *argv[]){    QApplication a(argc, argv);    MyWindow w;    w.setWidth(640);    w.setHeight(480);    w.setTitle(QString::fromLocal8Bit("爱看书的小沐"));    w.show();    return a.exec();}

mywindow.h

#ifndef WINDOW_H#define WINDOW_H#include <QOpenGLWindow>#include <QOpenGLFunctions>#include <QTimer>class MyWindow : public QOpenGLWindow, protected QOpenGLFunctions{    Q_OBJECTpublic:    MyWindow();    ~MyWindow();protected:    void initializeGL();          //初始化设置    void resizeGL(int w, int h);  //窗口尺寸变化响应函数    void paintGL();               //重绘响应函数private:    GLfloat angle;                //定义旋转角度    QTimer *timer;                //定义新的定时器};#endif // WINDOW_H

mywindow.cpp

#include "mywindow.h"MyWindow::MyWindow(){    timer = new QTimer();    angle = 0.0;    connect(timer, SIGNAL(timeout()), this, SLOT(update()));    timer->start(100);}MyWindow::~MyWindow(){}void MyWindow::initializeGL(){    initializeOpenGLFunctions();    glClearColor(0.0,0.0,0.0,0.0);    glClearDepth(1.0);}void MyWindow::resizeGL(int w, int h){    Q_UNUSED(w);    Q_UNUSED(h);}void MyWindow::paintGL(){    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);    glLoadIdentity();    glRotated(angle,0.0,1.0,0.0);    glBegin(GL_TRIANGLES);        glColor3f(1.0,0.0,0.0);        glVertex3f(0.0,0.8,0.0);        glColor3f(0.0,0.0,1.0);        glVertex3f(0.5,0.0,0.0);        glColor3f(0.0,1.0,0.0);        glVertex3f(-0.5,0.0,0.0);    glEnd();    angle+=10.0;}

程序运行如下：

5、Qt + glut

https://freeglut.sourceforge.net/

freeglut是OpenGL实用工具工具包（GLUT）库的免费软件/开源替代品。GLUT最初由Mark Kilgard编写，用于支持OpenGL“红皮书”第二版中的示例程序。从那时起，GLUT就被广泛应用于各种实际应用中，因为它简单、可用性广、便携性强。
GLUT（以及freeglut）负责创建窗口、初始化OpenGL上下文和处理输入事件所需的所有特定于系统的家务，以实现真正可移植的OpenGL程序。
freeglut是在X-Consortium许可下发布的。

untitled4.pro

LIBS += -L$$PWD\lib -lfreeglutCONFIG += c++11DEFINES += QT_DEPRECATED_WARNINGSINCLUDEPATH += includeSOURCES += \    main.cpp

main.cpp

#include "GL/glut.h"void display(void){    // clear all pixels    glClear(GL_COLOR_BUFFER_BIT);    glColor3f(0.5, 0.1, 1.0);    glBegin(GL_POLYGON);    glVertex3f(0.20, 0.20, 0.0);    glVertex3f(0.80, 0.20, 0.0);    glVertex3f(0.80, 0.80, 0.0);    glVertex3f(0.20, 0.80, 0.0);    glEnd();    glFlush();}void init(void){    // select clearing color: blue    glClearColor(0.0, 1.0, 0.0, 0.0);    // initialize viewing values    glMatrixMode(GL_PROJECTION);    glLoadIdentity();    glOrtho(0.0, 1.0, 0.0, 1.0, -1.0, 1.0);}int main(int argc, char *argv[]){    glutInit(&argc, argv);    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);    glutInitWindowSize(640, 240);    glutInitWindowPosition(480, 320);    glutCreateWindow("爱看书的小沐");    init();    glutDisplayFunc(display);    glutMainLoop();    return 0;}

程序运行后：

6、Qt + glfw

https://www.glfw.org/

GLFW是一个开源、多平台的库，用于OpenGL、OpenGL ES和Vulkan在桌面上的开发。它提供了一个简单的API，用于创建窗口、上下文和表面，接收输入和事件。
GLFW是用C语言编写的，支持Windows、macOS、Wayland和X11。
GLFW是根据zlib/libpng许可证获得许可的。

untitled4.pro

LIBS += -L$$PWD\lib -lglfw3 -lopengl32 -lGlU32 -luser32 -lkernel32 -lgdi32CONFIG += c++11DEFINES += QT_DEPRECATED_WARNINGSINCLUDEPATH += includeSOURCES += \    main.cpp

main.cpp

#include <iostream>#include "GLFW/glfw3.h"using namespace std;int main(int argc, char *argv[]){    GLFWwindow* window;    /* Initialize the library */    if (!glfwInit())        return -1;    /* Create a windowed mode window and its OpenGL context */    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);    if (!window)    {        glfwTerminate();        return -1;    }    /* Make the window's context current */    glfwMakeContextCurrent(window);    /* Loop until the user closes the window */    while (!glfwWindowShouldClose(window))    {        /* Render here */        glClear(GL_COLOR_BUFFER_BIT);        /* Swap front and back buffers */        glfwSwapBuffers(window);        /* Poll for and process events */        glfwPollEvents();    }    glfwTerminate();    return 0;}

程序运行如下：

结语

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