基于Qt的OpenGL学习（6）—— 摄像机

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 v1.6，喜欢就点个Star吧~

不同点 (仅列出新增)

1. Qt中封装的OpenGL相关的类之前基本都对比完了，其余部分基本还是用glxxx()的函数，后面可能就只在QtFunctionWidget.cpp中修改了。
2. 我的更新是通过QTimer调用update()实现的，就没有计算教程中的时间差了。

运行结果

修改的文件

QtFunctionWidget.h

#ifndef QTFUNCTIONWIDGET_H
#define QTFUNCTIONWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLShaderProgram>
#include <QOpenGLFunctions>
#include <QOpenGLVertexArrayObject>
#include <QOpenGLBuffer>
#include <QOpenGLTexture>

#include "Camera.h"

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;

    void keyPressEvent(QKeyEvent *event) Q_DECL_OVERRIDE;
    void keyReleaseEvent(QKeyEvent *event) Q_DECL_OVERRIDE;
    void mousePressEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
    void mouseReleaseEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
    void mouseMoveEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
    void wheelEvent(QWheelEvent *event) Q_DECL_OVERRIDE;

private:
    QOpenGLShaderProgram shaderProgram;
    QOpenGLBuffer vbo;
    QOpenGLVertexArrayObject vao;
    QOpenGLTexture *texture1 = nullptr;
    QOpenGLTexture *texture2 = nullptr;

    QTimer* m_pTimer = nullptr;
    int     m_nTimeValue = 0;

    // camera
    std::unique_ptr<Camera> camera;
    bool m_bLeftPressed;
    QPoint m_lastPos;
};

#endif // QTFUNCTIONWIDGET_H

QtFunctionWidget.cpp

#include "QtFunctionWidget.h"
#include <QDebug>
#include <QTimer>

QtFunctionWidget::QtFunctionWidget(QWidget *parent) : QOpenGLWidget (parent),
    vbo(QOpenGLBuffer::VertexBuffer)
{
    camera = std::make_unique<Camera>(QVector3D(5.0f, 0.0f, 10.0f));
    m_bLeftPressed = false;

    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();
    }

    //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);

    vbo.release();

    // configure global opengl state
    // -----------------------------
    glEnable(GL_DEPTH_TEST);
}

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!

    camera->processInput(1.0f);

    // bind textures on corresponding texture units
    glActiveTexture(GL_TEXTURE0);
    texture1->bind();
    glActiveTexture(GL_TEXTURE1);
    texture2->bind();

    shaderProgram.bind();

    QMatrix4x4 projection;
    projection.perspective(camera->zoom, 1.0f * width() / height(), 0.1f, 100.f);
    shaderProgram.setUniformValue("projection", projection);

    // camera/view transformation
    shaderProgram.setUniformValue("view", camera->getViewMatrix());

    {// 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();
}

void QtFunctionWidget::keyPressEvent(QKeyEvent *event)
{
    int key = event->key();
    if (key >= 0 && key < 1024)
        camera->keys[key] = true;
}

void QtFunctionWidget::keyReleaseEvent(QKeyEvent *event)
{
    int key = event->key();
    if (key >= 0 && key < 1024)
        camera->keys[key] = false;
}

void QtFunctionWidget::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton){
        m_bLeftPressed = true;
        m_lastPos = event->pos();
    }
}

void QtFunctionWidget::mouseReleaseEvent(QMouseEvent *event)
{
    Q_UNUSED(event);

    m_bLeftPressed = false;
}

void QtFunctionWidget::mouseMoveEvent(QMouseEvent *event)
{
    if (m_bLeftPressed) {
        int xpos = event->pos().x();
        int ypos = event->pos().y();

        int xoffset = xpos - m_lastPos.x();
        int yoffset = m_lastPos.y() - ypos;
        m_lastPos = event->pos();
        camera->processMouseMovement(xoffset, yoffset);
    }
}

void QtFunctionWidget::wheelEvent(QWheelEvent *event)
{
    QPoint offset = event->angleDelta();
    camera->processMouseScroll(offset.y()/20.0f);
}

Camera.h

#ifndef CAMERA_H
#define CAMERA_H

#include <QVector3D>
#include <QMatrix4x4>
#include <QKeyEvent>

// Defines several possible options for camera movement. Used as abstraction to stay away from window-system specific input methods
enum Camera_Movement {
  FORWARD,
  BACKWARD,
  LEFT,
  RIGHT,
  UP,
  DOWN
};

// Default camera values
const float YAW = -90.0f;
const float PITCH = 0.0f;
const float SPEED = 1.0f;
const float SENSITIVITY = 0.01f;
const float ZOOM = 45.0f;

class Camera {
public:
    Camera(QVector3D position = QVector3D(0.0f, 0.0f, 0.0f), QVector3D up = QVector3D(0.0f, 1.0f, 0.0f),
    float yaw = YAW, float pitch = PITCH);
    ~Camera();

    QMatrix4x4 getViewMatrix();
    void processMouseMovement(float xoffset, float yoffset, bool constraintPitch = true);
    void processMouseScroll(float yoffset);
    void processInput(float dt);

    QVector3D position;
    QVector3D worldUp;
    QVector3D front;

    QVector3D up;
    QVector3D right;

    //Eular Angles
    float picth;
    float yaw;

    //Camera options
    float movementSpeed;
    float mouseSensitivity;
    float zoom;

    //Keyboard multi-touch
    bool keys[1024];
private:
    void updateCameraVectors();
    void processKeyboard(Camera_Movement direction, float deltaTime);
};

#endif // CAMERA_H

Camera.cpp

#include "Camera.h"
#include <QDebug>

Camera::Camera(QVector3D position, QVector3D up, float yaw, float pitch) :
    position(position),
    worldUp(up),
    front(-position),
    picth(pitch),
    yaw(yaw),
    movementSpeed(SPEED),
    mouseSensitivity(SENSITIVITY),
    zoom(ZOOM) {
    this->updateCameraVectors();

    for(uint i = 0; i != 1024; ++i)
        keys[i] = false;
}

Camera::~Camera()
{

}

// Returns the view matrix calculated using Euler Angles and the LookAt Matrix
QMatrix4x4 Camera::getViewMatrix()
{
    QMatrix4x4 view;
    view.lookAt(this->position, this->position + this->front, this->up);
    return view;
}

// Processes input received from any keyboard-like input system. Accepts input parameter in the form of camera defined ENUM (to abstract it from windowing systems)
void Camera::processKeyboard(Camera_Movement direction, float deltaTime)
{
    float velocity = this->movementSpeed * deltaTime;
    if (direction == FORWARD)
        this->position += this->front * velocity;
    if (direction == BACKWARD)
        this->position -= this->front * velocity;
  if (direction == LEFT)
    this->position -= this->right * velocity;
  if (direction == RIGHT)
    this->position += this->right * velocity;
  if (direction == UP)
    this->position += this->worldUp * velocity;
  if (direction == DOWN)
    this->position -= this->worldUp * velocity;
}

// Processes input received from a mouse input system. Expects the offset value in both the x and y direction.
void Camera::processMouseMovement(float xoffset, float yoffset, bool constraintPitch)
{
  xoffset *= this->mouseSensitivity;
  yoffset *= this->mouseSensitivity;

  this->yaw += xoffset;
  this->picth += yoffset;

  if (constraintPitch) {
    if (this->picth > 89.0f)
      this->picth = 89.0f;
    if (this->picth < -89.0f)
      this->picth = -89.0f;
  }

  this->updateCameraVectors();
}

// Processes input received from a mouse scroll-wheel event. Only requires input on the vertical wheel-axis
void Camera::processMouseScroll(float yoffset)
{
  if (this->zoom >= 1.0f && this->zoom <= 45.0f)
    this->zoom -= yoffset;
  if (this->zoom > 45.0f)
    this->zoom = 45.0f;
  if (this->zoom < 1.0f)
      this->zoom = 1.0f;
}

void Camera::processInput(float dt)
{

    if (keys[Qt::Key_W])
      processKeyboard(FORWARD, dt);
    if (keys[Qt::Key_S])
      processKeyboard(BACKWARD, dt);
    if (keys[Qt::Key_A])
      processKeyboard(LEFT, dt);
    if (keys[Qt::Key_D])
      processKeyboard(RIGHT, dt);
    if (keys[Qt::Key_E])
      processKeyboard(UP, dt);
    if (keys[Qt::Key_Q])
      processKeyboard(DOWN, dt);
}

void Camera::updateCameraVectors()
{
    // Calculate the new Front vector
    QVector3D front;
    front.setX(cos(this->yaw) * cos(this->picth));
    front.setY(sin(this->picth));
    front.setZ(sin(this->yaw) * cos(this->picth));
    this->front = front.normalized();
    this->right = QVector3D::crossProduct(this->front, this->worldUp).normalized();
    this->up = QVector3D::crossProduct(this->right, this->front).normalized();
}

参考链接

• https://blog.csdn.net/z136411501/article/details/79939695