基于Qt的OpenGL学习（5）—— 坐标系统
2019-08-09 本文已影响0人
玖零儛
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)
- view、projection矩阵只需要初始化一次，就放到了
initializeGL()中。 - 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();
}
