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，准备后期每篇教程一个commit，查看本篇代码 git checkout v1.1，喜欢就点个Star吧~

不同点

原教程关于ShaderProgram的读取、链接很繁琐，后面教程还专门写了个类Shader，这里我直接使用Qt封装好的addShaderFromSourceFile函数更方便。

Qt提供了QOpenGLShaderProgram、QOpenGLVertexArrayObject、QOpenGLBuffer这些类来处理OpenGL中的program、VAO、VBO。

运行结果

运行结果

使用OpenGL函数版

CoreFunctionWidget.h

#ifndef COREFUNCTIONWIDGET_H

#define COREFUNCTIONWIDGET_H

#include

#include

#include

#include

#include

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;

};

#endif // COREFUNCTIONWIDGET_H

CoreFunctionWidget.cpp

#include "CoreFunctionWidget.h"

#include

#include

static GLuint VBO, VAO, EBO;

CoreFunctionWidget::CoreFunctionWidget(QWidget *parent) : QOpenGLWidget(parent)

{

}

CoreFunctionWidget::~CoreFunctionWidget()

{

glDeleteVertexArrays(1, &VAO);

glDeleteBuffers(1, &VBO);

// glDeleteBuffers(1, &EBO);

}

void CoreFunctionWidget::initializeGL(){

this->initializeOpenGLFunctions();

bool success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/triangle.vert");

if (!success) {

qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();

return;

}

success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/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

//线框模式，QOpenGLExtraFunctions没这函数, 3_3_Core有

// glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

}

void CoreFunctionWidget::resizeGL(int w, int h){

glViewport(0, 0, w, h);

}

void CoreFunctionWidget::paintGL(){

glClearColor(0.2f, 0.3f, 0.3f, 1.0f);

glClear(GL_COLOR_BUFFER_BIT);

shaderProgram.bind();

glBindVertexArray(VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized

// glDrawArrays(GL_TRIANGLES, 0, 6);

glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

shaderProgram.release();

}

使用Qt相关函数版

QtFunctionWidget.h

#ifndef QTFUNCTIONWIDGET_H

#define QTFUNCTIONWIDGET_H

#include

#include

#include

#include

#include

#include

#include

#include

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

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, ":/triangle.vert");

if (!success) {

qDebug() << "shaderProgram addShaderFromSourceFile failed!" << shaderProgram.log();

return;

}

success = shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/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[] = {

0.5f, 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

};

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, 0.3f, 0.3f, 1.0f);

glClear(GL_COLOR_BUFFER_BIT);

shaderProgram.bind();

{

QOpenGLVertexArrayObject::Binder vaoBind(&vao);

glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

}

shaderProgram.release();

}

GLSL

triangle.vert

#version 330 core

layout(location = 0) in vec3 aPos;

void main(){

gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0f);

}

triangle.frag

#version 330 core

out vec4 FragColor;

void main(){

FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);

}

main.cpp

#include

#include "MainWindow.h"

#include "QtFunctionWidget.h"

#include "CoreFunctionWidget.h"

int main(int argc, char *argv[])

{

QApplication a(argc, argv);

// MainWindow w;

QtFunctionWidget w1;

CoreFunctionWidget w2;

w1.setWindowTitle(QObject::tr("QtFunction"));

w2.setWindowTitle(QObject::tr("CoreFunction"));

w1.show();

w2.show();

return a.exec();

}