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基于Qt的OpenGL学习(5)—— 坐标系统

基于Qt的OpenGL学习(5)—— 坐标系统

作者: 玖零儛 | 来源:发表于2019-08-09 13:33 被阅读0次

    简介

    要学习OpenGL的话,强烈安利这个教程JoeyDeVries的learnopengl,这里是中文翻译好的版本。教程中使用OpenGL是通过GLFW这个库,而在Qt中对OpenGL封装得很好,并且和GUI以及IO相关的处理Qt更便捷,学习起来更轻松。这里就对每篇教程,在Qt在分别直接使用OpenGL的函数和Qt封装好的类以作对比。
    教程中使用的OpenGL版本为3.3,在Qt中需要使用此版本的OpenGL只需要继承类QOpenGLFunctions_3_3_Core即可。如果为了在不同设备上都能用OpenGL的话,Qt提供了类QOpenGLFunctions,这个类包含了大部分公共的函数,可能会有个别函数不能用。

    对比说明

    教程地址

    原教程地址,相关知识可以点击链接学习。
    我的工程地址,每篇教程一个commit,可以切换着看,查看本篇代码 git checkout v1.5,喜欢就点个Star吧~

    不同点 (仅列出新增)

    1. view、projection矩阵只需要初始化一次,就放到了initializeGL()中。
    2. 原教程最中间的矩形不转是因为教程里循环赋值角度第0个时:angle = 0 * value。

    运行结果

    运行结果

    使用OpenGL函数版

    CoreFunctionWidget.h

    #ifndef COREFUNCTIONWIDGET_H
    #define COREFUNCTIONWIDGET_H
    
    #include <QOpenGLWidget>
    #include <QOpenGLExtraFunctions>
    #include <QOpenGLFunctions_3_3_Core>
    #include <QOpenGLShader>
    #include <QOpenGLShaderProgram>
    
    class CoreFunctionWidget : public QOpenGLWidget
                               , protected /*QOpenGLExtraFunctions*/QOpenGLFunctions_3_3_Core
    {
        Q_OBJECT
    public:
        explicit CoreFunctionWidget(QWidget *parent = nullptr);
        ~CoreFunctionWidget();
    
    protected:
        virtual void initializeGL();
        virtual void resizeGL(int w, int h);
        virtual void paintGL();
    
    private:
        QOpenGLShaderProgram shaderProgram;
    
        QTimer* m_pTimer = nullptr;
        int     m_nTimeValue = 0;
    };
    
    #endif // COREFUNCTIONWIDGET_H
    

    CoreFunctionWidget.cpp

    #include "CoreFunctionWidget.h"
    #include <QDebug>
    #include <QTimer>
    
    static GLuint VBO, VAO, texture1, texture2;
    
    CoreFunctionWidget::CoreFunctionWidget(QWidget *parent) : QOpenGLWidget(parent)
    {
        m_pTimer = new QTimer(this);
        connect(m_pTimer, &QTimer::timeout, this, [=]{
            m_nTimeValue += 1;
            update();
        });
        m_pTimer->start(40);
    }
    
    CoreFunctionWidget::~CoreFunctionWidget()
    {
        glDeleteVertexArrays(1, &VAO);
        glDeleteBuffers(1, &VBO);
    }
    
    void CoreFunctionWidget::initializeGL(){
        this->initializeOpenGLFunctions();
    
        bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/textures.vert");
        if (!success) {
            qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
            return;
        }
    
        success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/textures.frag");
        if (!success) {
            qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
            return;
        }
    
        success = shaderProgram.link();
        if(!success) {
            qDebug() << "shaderProgram link failed!" << shaderProgram.log();
        }
    
        // configure global opengl state
        // -----------------------------
        glEnable(GL_DEPTH_TEST);
    
        //VAO,VBO data
        float vertices[] = {
            -0.5f, -0.5f, -0.5f,  0.0f, 0.0f,
             0.5f, -0.5f, -0.5f,  1.0f, 0.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
            -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 0.0f,
    
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
             0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 1.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 1.0f,
            -0.5f,  0.5f,  0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
    
            -0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
            -0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
            -0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
    
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
             0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
    
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  1.0f, 1.0f,
             0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
             0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
    
            -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
            -0.5f,  0.5f,  0.5f,  0.0f, 0.0f,
            -0.5f,  0.5f, -0.5f,  0.0f, 1.0f
        };
    
        glGenVertexArrays(1, &VAO);
        glGenBuffers(1, &VBO);
        // 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);
    
        // position attribute
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
        glEnableVertexAttribArray(0);
        // texture coord attribute
        glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
        glEnableVertexAttribArray(1);
    
        // texture 1
        // ---------
        glGenTextures(1, &texture1);
        glBindTexture(GL_TEXTURE_2D, texture1);
         // set the texture wrapping parameters
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);   // set texture wrapping to GL_REPEAT (default wrapping method)
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        // set texture filtering parameters
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        // load image, create texture and generate mipmaps
        QImage img1 = QImage(":/container.jpg").convertToFormat(QImage::Format_RGB888);
        if (!img1.isNull()) {
            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, img1.width(), img1.height(), 0, GL_RGB, GL_UNSIGNED_BYTE, img1.bits());
            glGenerateMipmap(GL_TEXTURE_2D);
        }
    
        // texture 2
        // ---------
        glGenTextures(1, &texture2);
        glBindTexture(GL_TEXTURE_2D, texture2);
        // set the texture wrapping parameters
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);   // set texture wrapping to GL_REPEAT (default wrapping method)
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        // set texture filtering parameters
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        // load image, create texture and generate mipmaps
        QImage img2 = QImage(":/awesomeface.png").convertToFormat(QImage::Format_RGBA8888).mirrored(true, true);
        if (!img2.isNull()) {
            // note that the awesomeface.png has transparency and thus an alpha channel, so make sure to tell OpenGL the data type is of GL_RGBA
            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img2.width(), img2.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, img2.bits());
            glGenerateMipmap(GL_TEXTURE_2D);
        }
    
        shaderProgram.bind();   // don't forget to activate/use the shader before setting uniforms!
        // tell opengl for each sampler to which texture unit it belongs to (only has to be done once)
        shaderProgram.setUniformValue("texture1", 0);
        shaderProgram.setUniformValue("texture2", 1);
        // note: currently we set the projection matrix each frame, but since the projection matrix rarely changes it's often best practice to set it outside the main loop only once.
        QMatrix4x4 view;
        view.translate(QVector3D(0.0f, 0.0f, -3.0f));
        shaderProgram.setUniformValue("view", view);
        QMatrix4x4 projection;
        projection.perspective(45.0f, 1.0f * width() / height(), 0.1f, 100.0f);
        shaderProgram.setUniformValue("projection", projection);
        shaderProgram.release();
    }
    
    void CoreFunctionWidget::resizeGL(int w, int h){
        glViewport(0, 0, w, h);
    }
    
    
    static QVector3D cubePositions[] = {
      QVector3D( 0.0f,  0.0f,  0.0f),
      QVector3D( 2.0f,  5.0f, -15.0f),
      QVector3D(-1.5f, -2.2f, -2.5f),
      QVector3D(-3.8f, -2.0f, -12.3f),
      QVector3D( 2.4f, -0.4f, -3.5f),
      QVector3D(-1.7f,  3.0f, -7.5f),
      QVector3D( 1.3f, -2.0f, -2.5f),
      QVector3D( 1.5f,  2.0f, -2.5f),
      QVector3D( 1.5f,  0.2f, -1.5f),
      QVector3D(-1.3f,  1.0f, -1.5f)
    };
    
    void CoreFunctionWidget::paintGL(){
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // also clear the depth buffer now!
    
        // bind textures on corresponding texture units
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, texture1);
        glActiveTexture(GL_TEXTURE1);
        glBindTexture(GL_TEXTURE_2D, texture2);
    
        shaderProgram.bind();
        // render boxes
        glBindVertexArray(VAO);
        for (unsigned int i = 0; i < 10; i++) {
           // calculate the model matrix for each object and pass it to shader before drawing
           QMatrix4x4 model;
           model.translate(cubePositions[i]);
           float angle = (i + 1.0f) * m_nTimeValue;
           model.rotate(angle, QVector3D(1.0f, 0.3f, 0.5f));
           shaderProgram.setUniformValue("model", model);
           glDrawArrays(GL_TRIANGLES, 0, 36);
        }
    
        shaderProgram.release();
    }
    

    使用Qt相关函数版

    QtFunctionWidget.h

    #ifndef QTFUNCTIONWIDGET_H
    #define QTFUNCTIONWIDGET_H
    
    #include <QOpenGLWidget>
    
    
    #include <QOpenGLWidget>
    #include <QOpenGLShader>
    #include <QOpenGLShaderProgram>
    #include <QOpenGLFunctions>
    #include <QOpenGLVertexArrayObject>
    #include <QOpenGLBuffer>
    #include <QOpenGLTexture>
    
    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;
        QOpenGLVertexArrayObject vao;
        QOpenGLTexture *texture1 = nullptr;
        QOpenGLTexture *texture2 = nullptr;
    
        QTimer* m_pTimer = nullptr;
        int     m_nTimeValue = 0;
    };
    
    #endif // QTFUNCTIONWIDGET_H
    

    QtFunctionWidget.cpp

    #include "QtFunctionWidget.h"
    #include <QDebug>
    #include <QTimer>
    
    QtFunctionWidget::QtFunctionWidget(QWidget *parent) : QOpenGLWidget (parent),
        vbo(QOpenGLBuffer::VertexBuffer)
    {
        m_pTimer = new QTimer(this);
        connect(m_pTimer, &QTimer::timeout, this, [=]{
            m_nTimeValue += 1;
            update();
        });
        m_pTimer->start(40);
    }
    
    QtFunctionWidget::~QtFunctionWidget(){
        makeCurrent();
    
        vbo.destroy();
        vao.destroy();
    
        delete texture1;
        delete texture2;
    
        doneCurrent();
    }
    
    void QtFunctionWidget::initializeGL(){
        this->initializeOpenGLFunctions();
    
        bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/textures.vert");
        if (!success) {
            qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
            return;
        }
    
        success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/textures.frag");
        if (!success) {
            qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();
            return;
        }
    
        success = shaderProgram.link();
        if(!success) {
            qDebug() << "shaderProgram link failed!" << shaderProgram.log();
        }
    
        // configure global opengl state
        // -----------------------------
        glEnable(GL_DEPTH_TEST);
    
        //VAO,VBO data
        float vertices[] = {
            -0.5f, -0.5f, -0.5f,  0.0f, 0.0f,
             0.5f, -0.5f, -0.5f,  1.0f, 0.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
            -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 0.0f,
    
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
             0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 1.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 1.0f,
            -0.5f,  0.5f,  0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
    
            -0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
            -0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
            -0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
    
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
             0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
    
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
             0.5f, -0.5f, -0.5f,  1.0f, 1.0f,
             0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
             0.5f, -0.5f,  0.5f,  1.0f, 0.0f,
            -0.5f, -0.5f,  0.5f,  0.0f, 0.0f,
            -0.5f, -0.5f, -0.5f,  0.0f, 1.0f,
    
            -0.5f,  0.5f, -0.5f,  0.0f, 1.0f,
             0.5f,  0.5f, -0.5f,  1.0f, 1.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
             0.5f,  0.5f,  0.5f,  1.0f, 0.0f,
            -0.5f,  0.5f,  0.5f,  0.0f, 0.0f,
            -0.5f,  0.5f, -0.5f,  0.0f, 1.0f
        };
    
        QOpenGLVertexArrayObject::Binder vaoBind(&vao);
    
        vbo.create();
        vbo.bind();
        vbo.allocate(vertices, sizeof(vertices));
    
        // position attribute
        int attr = -1;
        attr = shaderProgram.attributeLocation("aPos");
        shaderProgram.setAttributeBuffer(attr, GL_FLOAT, 0, 3, sizeof(GLfloat) * 5);
        shaderProgram.enableAttributeArray(attr);
        // texture coord attribute
        attr = shaderProgram.attributeLocation("aTexCoord");
        shaderProgram.setAttributeBuffer(attr, GL_FLOAT, sizeof(GLfloat) * 3, 2, sizeof(GLfloat) * 5);
        shaderProgram.enableAttributeArray(attr);
    
        // texture 1
        // ---------
        texture1 = new QOpenGLTexture(QImage(":/container.jpg"), QOpenGLTexture::GenerateMipMaps);
        if(!texture1->isCreated()){
            qDebug() << "Failed to load texture";
        }
        // set the texture wrapping parameters
        texture1->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);
        texture1->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);
        // set texture filtering parameters
        texture1->setMinificationFilter(QOpenGLTexture::Linear);
        texture1->setMagnificationFilter(QOpenGLTexture::Linear);
    
        // texture 2
        // ---------
        texture2 = new QOpenGLTexture(QImage(":/awesomeface.png").mirrored(true, true), QOpenGLTexture::GenerateMipMaps);
        if(!texture2->isCreated()){
            qDebug() << "Failed to load texture";
        }
        // set the texture wrapping parameters
        texture2->setWrapMode(QOpenGLTexture::DirectionS, QOpenGLTexture::Repeat);
        texture2->setWrapMode(QOpenGLTexture::DirectionT, QOpenGLTexture::Repeat);
        // set texture filtering parameters
        texture2->setMinificationFilter(QOpenGLTexture::Linear);
        texture1->setMagnificationFilter(QOpenGLTexture::Linear);
    
        // tell opengl for each sampler to which texture unit it belongs to (only has to be done once)
        shaderProgram.bind();   // don't forget to activate/use the shader before setting uniforms!
        shaderProgram.setUniformValue("texture1", 0);
        shaderProgram.setUniformValue("texture2", 1);
        // note: currently we set the projection matrix each frame, but since the projection matrix rarely changes it's often best practice to set it outside the main loop only once.
        QMatrix4x4 view;
        view.translate(QVector3D(0.0f, 0.0f, -3.0f));
        shaderProgram.setUniformValue("view", view);
        QMatrix4x4 projection;
        projection.perspective(45.0f, 1.0f * width() / height(), 0.1f, 100.0f);
        shaderProgram.setUniformValue("projection", projection);
        shaderProgram.release();
    
        vbo.release();
    }
    
    void QtFunctionWidget::resizeGL(int w, int h){
        glViewport(0, 0, w, h);
    }
    
    static QVector3D cubePositions[] = {
      QVector3D( 0.0f,  0.0f,  0.0f),
      QVector3D( 2.0f,  5.0f, -15.0f),
      QVector3D(-1.5f, -2.2f, -2.5f),
      QVector3D(-3.8f, -2.0f, -12.3f),
      QVector3D( 2.4f, -0.4f, -3.5f),
      QVector3D(-1.7f,  3.0f, -7.5f),
      QVector3D( 1.3f, -2.0f, -2.5f),
      QVector3D( 1.5f,  2.0f, -2.5f),
      QVector3D( 1.5f,  0.2f, -1.5f),
      QVector3D(-1.3f,  1.0f, -1.5f)
    };
    
    void QtFunctionWidget::paintGL(){
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // also clear the depth buffer now!
    
        // bind textures on corresponding texture units
        glActiveTexture(GL_TEXTURE0);
        texture1->bind();
        glActiveTexture(GL_TEXTURE1);
        texture2->bind();
    
        shaderProgram.bind();
    
        {// render box
            QOpenGLVertexArrayObject::Binder vaoBind(&vao);
    
            for (unsigned int i = 0; i < 10; i++) {
               // calculate the model matrix for each object and pass it to shader before drawing
               QMatrix4x4 model;
               model.translate(cubePositions[i]);
               float angle = (i + 1.0f) * m_nTimeValue;
               model.rotate(angle, QVector3D(1.0f, 0.3f, 0.5f));
               shaderProgram.setUniformValue("model", model);
               glDrawArrays(GL_TRIANGLES, 0, 36);
            }
        }
    
        texture1->release();
        texture2->release();
        shaderProgram.release();
    }
    

    GLSL

    textures.vert

    #version 330 core
    layout (location = 0) in vec3 aPos;
    layout (location = 1) in vec2 aTexCoord;
     
    out vec2 TexCoord;
     
    uniform mat4 model;
    uniform mat4 view;
    uniform mat4 projection;
     
    void main(){
      gl_Position = projection * view * model * vec4(aPos, 1.0f);
      TexCoord = aTexCoord;
    }
    

    textures.frag

    #version 330 core
    out vec4 FragColor;
     
    in vec2 TexCoord;
     
    uniform sampler2D texture1;
    uniform sampler2D texture2;
     
    void main()
    {
        FragColor = mix(texture2D(texture1, TexCoord), texture2D(texture2, TexCoord), 0.2f);
    }
    

    main.cpp

    #include <QApplication>
    #include "QtFunctionWidget.h"
    #include "CoreFunctionWidget.h"
    
    int main(int argc, char *argv[])
    {
        QApplication a(argc, argv);
    
        QtFunctionWidget w1;
        CoreFunctionWidget w2;
    
        w1.setWindowTitle(QObject::tr("QtFunction"));
        w2.setWindowTitle(QObject::tr("CoreFunction"));
    
        w1.show();
        w2.show();
    
        return a.exec();
    }
    

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