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OpenGL development with QT (II) drawing cube
2022-07-29 01:39:00 【Manon Feifei】
stay OpenGL Medium and three-dimensional entities will be split into small plane graphics for rendering . For example, the cube we draw , It can be divided into six planes to draw . Here we use a textured cube to illustrate the rendering method of three-dimensional entities .
Draw a cube
Because the cube has many points , In order to improve the encapsulation of data, we define a structure to represent the spatial coordinates and texture coordinates of each point .
struct CubePoint {
QVector3D posCoord; // Spatial coordinates
QVector2D textureCoord; // Texture coordinates
CubePoint(const QVector3D& position = QVector3D(),
const QVector2D& texture = QVector2D()):
posCoord(position), textureCoord(texture) {
}
};
After adding the data structure of each point of the cube , We can add the corresponding coordinate information . The coordinate diagram of the cube is shown below :
Initialize the position information and texture information of each vertex in the program :
//QVector<CubePoint> m_data;
//m_data It is the data container of vertex information
void SimpleGLWindow::initializeCubeData()
{
// Cube six corresponding data
m_data = {
// FRONT FACE
{
{
-0.5, -0.5, 0.5}, {
0, 0}}, {
{
0.5, -0.5, 0.5}, {
1, 0}},
{
{
0.5, 0.5, 0.5}, {
1, 1}}, {
{
-0.5, 0.5, 0.5}, {
0, 1}},
// TOP FACE
{
{
-0.5, 0.5, 0.5}, {
0, 0}}, {
{
0.5, 0.5, 0.5}, {
1, 0}},
{
{
0.5, 0.5, -0.5}, {
1, 1}}, {
{
-0.5, 0.5, -0.5}, {
0, 1}},
// BACK FACE
{
{
-0.5, 0.5, -0.5}, {
0, 0}}, {
{
0.5, 0.5, -0.5}, {
1, 0}},
{
{
0.5, -0.5, -0.5}, {
1, 1}}, {
{
-0.5, -0.5, -0.5}, {
0, 1}},
// BOTTOM FACE
{
{
-0.5, -0.5, -0.5}, {
0, 0}}, {
{
0.5, -0.5, -0.5}, {
1, 0}},
{
{
0.5, -0.5, 0.5}, {
1, 1}}, {
{
-0.5, -0.5, 0.5}, {
0, 1}},
// LEFT FACE
{
{
-0.5, -0.5, -0.5}, {
0, 0}}, {
{
-0.5, -0.5, 0.5}, {
1, 0}},
{
{
-0.5, 0.5, 0.5}, {
1, 1}}, {
{
-0.5, 0.5, -0.5}, {
0, 1}},
// RIGHT FACE
{
{
0.5, -0.5, 0.5}, {
0, 0}}, {
{
0.5, -0.5, -0.5}, {
1, 0}},
{
{
0.5, 0.5, -0.5}, {
1, 1}}, {
{
0.5, 0.5, 0.5}, {
0, 1}},
};
}
stay initializeGL() Call the data initialization method :
void SimpleGLWindow::initializeGL()
{
...
// Open depth test
glEnable(GL_DEPTH_TEST);
// Turn on the culling effect
glEnable(GL_CULL_FACE);
// Disable the lighting and shadow effects of the back , Avoid unnecessary calculations
glCullFace(GL_BACK);
// Initialization data
initializeCubeData();
// Set the default color when refreshing the display to RGB(255,255,255)
glClearColor(1, 1, 1, 0);
}
After data initialization , We can draw the cube in the drawing method , The corresponding drawing operations are as follows :
void SimpleGLWindow::paintGL()
{
// Empty the color cache and depth cache
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// take OpenGL The viewport and window remain the same
glViewport(0, 0, width(), height());
// Reset the transformation matrix
glLoadIdentity();
// Rotate the view for convenience
//m_angle It's the angle of rotation
glRotatef(m_angle, 1.0, 0.0, 0.0);
glRotatef(m_angle, 0.0, 1.0, 0.0);
// Bind texture
if(m_texture)
{
m_texture->bind();
}
// Start texture
glEnable(GL_TEXTURE_2D);
// Draw a cube
glBegin(GL_QUADS);
for(const CubePoint &point: m_data) {
glTexCoord2d(point.textureCoord.x(), point.textureCoord.y());
glVertex3f(point.posCoord.x(), point.posCoord.y(), point.posCoord.z());
}
glEnd();
// Turn off texture
glDisable(GL_TEXTURE_2D);
}
The effect drawn is as follows :
Cube animation
The cube drawn by the above method is static . In order to make the graph not so monotonous , We add a timer to make the cube rotate , The corresponding implementation is as follows :
SimpleGLWindow::SimpleGLWindow(QWindow *parent) :
QOpenGLWindow(NoPartialUpdate, parent)
{
// Set the value of multisampling
QSurfaceFormat fmt = format();
fmt.setSamples(25);
setFormat(fmt);
// Set the timer to modify the value of rotation
QTimer* timer = new QTimer(this);
timer->setInterval(30);
connect(timer,&QTimer::timeout,this,[&](){
m_angle+=1;this->update();});
timer->start();
}
The display effect is as follows :
In addition to the timer , We can also use a more flexible animation framework to make the cube move , The corresponding settings are as follows :
//simpleglwindow.h
class SimpleGLWindow : public QOpenGLWindow, protected QOpenGLFunctions_1_1
{
Q_OBJECT
Q_PROPERTY(float angle READ angle WRITE setAngle)
public:
qreal angle() const;
void setAngle(const qreal &angle);
private:
qreal m_angle = 60;
...
};
//simpleglwindow.cpp
SimpleGLWindow::SimpleGLWindow(QWindow *parent) :
QOpenGLWindow(NoPartialUpdate, parent)
{
// Set the value of multisampling
QSurfaceFormat fmt = format();
fmt.setSamples(25);
setFormat(fmt);
QPropertyAnimation *animation = new QPropertyAnimation(this);
animation->setTargetObject(this);
animation->setPropertyName("angle");
animation->setStartValue(0);
animation->setEndValue(359);
animation->setDuration(5000);
animation->setLoopCount(-1);
animation->setEasingCurve(QEasingCurve::InCubic);
animation->start();
}
qreal SimpleGLWindow::angle() const
{
return m_angle;
}
void SimpleGLWindow::setAngle(const qreal &angle)
{
m_angle = angle;
this->update();
}
The display effect is as follows :
Complete engineering code , Welcome to :
//simpleglwindow.h
#pragma execution_character_set("utf-8")
#ifndef SIMPLEGLWINDOW_H
#define SIMPLEGLWINDOW_H
#include <QOpenGLWindow>
#include <QOpenGLFunctions_1_1>
#include <QOpenGLTexture>
#include <QVector3D>
#include <QVector2D>
#include <QTimer>
#include <QObject>
// The use of OpenGLFunction The version is 1.1
class SimpleGLWindow : public QOpenGLWindow, protected QOpenGLFunctions_1_1
{
Q_OBJECT
Q_PROPERTY(float angle READ angle WRITE setAngle)
public:
SimpleGLWindow(QWindow *parent = 0);
qreal angle() const;
void setAngle(const qreal &angle);
protected:
// Initialization operation
void initializeGL();
// Draw function
void paintGL();
protected:
// Event of window size change
void resizeGL(int w, int h);
private:
void initialTexture();
// Initialize cube data
void initializeCubeData();
//OpenGL texture
QOpenGLTexture* m_texture = nullptr;
// Texture image
QImage* m_texture_image = nullptr;
struct CubePoint {
QVector3D posCoord; // Spatial coordinates
QVector2D textureCoord; // Texture coordinates
CubePoint(const QVector3D& position = QVector3D(),
const QVector2D& texture = QVector2D()):
posCoord(position), textureCoord(texture) {
}
};
qreal m_angle = 60;
QVector<CubePoint> m_data;
};
#endif // SIMPLEGLWINDOW_H
//simpleglwindow.cpp
#include "simpleglwindow.h"
#include <QDebug>
#include <QPropertyAnimation>
SimpleGLWindow::SimpleGLWindow(QWindow *parent) :
QOpenGLWindow(NoPartialUpdate, parent)
{
// Set the value of multisampling
QSurfaceFormat fmt = format();
fmt.setSamples(25);
setFormat(fmt);
QPropertyAnimation *animation = new QPropertyAnimation(this);
animation->setTargetObject(this);
animation->setPropertyName("angle");
animation->setStartValue(0);
animation->setEndValue(359);
animation->setDuration(5000);
animation->setLoopCount(-1);
animation->setEasingCurve(QEasingCurve::InCubic);
animation->start();
// QTimer* timer = new QTimer(this);
// timer->setInterval(30);
// connect(timer,&QTimer::timeout,this,[&](){m_angle+=1;this->update();});
// timer->start();
}
void SimpleGLWindow::initializeGL()
{
// initialization OpenGL function
if (!initializeOpenGLFunctions())
{
qDebug() << "init opengl functions failed";
}
initialTexture();
// Open depth test
glEnable(GL_DEPTH_TEST);
// Turn on the culling effect
glEnable(GL_CULL_FACE);
// Disable the lighting and shadow effects of the back , Avoid unnecessary calculations
glCullFace(GL_BACK);
initializeCubeData();
// Set the default color when refreshing the display to RGB(255,255,255)
glClearColor(1, 1, 1, 0);
}
void SimpleGLWindow::paintGL()
{
// Empty the color cache and depth cache
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// take OpenGL The viewport and window remain the same
glViewport(0, 0, width(), height());
// Reset the transformation matrix
glLoadIdentity();
// Rotate the view for convenience
glRotatef(m_angle, 1.0, 0.0, 0.0);
glRotatef(m_angle, 0.0, 1.0, 0.0);
// Bind texture
if(m_texture)
{
m_texture->bind();
}
// Start texture
glEnable(GL_TEXTURE_2D);
glBegin(GL_QUADS);
for(const CubePoint &point: m_data) {
glTexCoord2d(point.textureCoord.x(), point.textureCoord.y());
glVertex3f(point.posCoord.x(), point.posCoord.y(), point.posCoord.z());
}
glEnd();
// Turn off texture
glDisable(GL_TEXTURE_2D);
}
void SimpleGLWindow::resizeGL(int w, int h)
{
qDebug() << w << h;
}
void SimpleGLWindow::initialTexture()
{
// Initialize pictures and textures
m_texture_image = new QImage(":/background.jpg");
m_texture = new QOpenGLTexture(m_texture_image->mirrored());
// Add filters for amplification and reduction
m_texture->setMinificationFilter(QOpenGLTexture::LinearMipMapLinear);
m_texture->setMagnificationFilter(QOpenGLTexture::Linear);
}
void SimpleGLWindow::initializeCubeData()
{
m_data = {
// FRONT FACE
{
{
-0.5, -0.5, 0.5}, {
0, 0}}, {
{
0.5, -0.5, 0.5}, {
1, 0}},
{
{
0.5, 0.5, 0.5}, {
1, 1}}, {
{
-0.5, 0.5, 0.5}, {
0, 1}},
// TOP FACE
{
{
-0.5, 0.5, 0.5}, {
0, 0}}, {
{
0.5, 0.5, 0.5}, {
1, 0}},
{
{
0.5, 0.5, -0.5}, {
1, 1}}, {
{
-0.5, 0.5, -0.5}, {
0, 1}},
// BACK FACE
{
{
-0.5, 0.5, -0.5}, {
0, 0}}, {
{
0.5, 0.5, -0.5}, {
1, 0}},
{
{
0.5, -0.5, -0.5}, {
1, 1}}, {
{
-0.5, -0.5, -0.5}, {
0, 1}},
// BOTTOM FACE
{
{
-0.5, -0.5, -0.5}, {
0, 0}}, {
{
0.5, -0.5, -0.5}, {
1, 0}},
{
{
0.5, -0.5, 0.5}, {
1, 1}}, {
{
-0.5, -0.5, 0.5}, {
0, 1}},
// LEFT FACE
{
{
-0.5, -0.5, -0.5}, {
0, 0}}, {
{
-0.5, -0.5, 0.5}, {
1, 0}},
{
{
-0.5, 0.5, 0.5}, {
1, 1}}, {
{
-0.5, 0.5, -0.5}, {
0, 1}},
// RIGHT FACE
{
{
0.5, -0.5, 0.5}, {
0, 0}}, {
{
0.5, -0.5, -0.5}, {
1, 0}},
{
{
0.5, 0.5, -0.5}, {
1, 1}}, {
{
0.5, 0.5, 0.5}, {
0, 1}},
};
}
qreal SimpleGLWindow::angle() const
{
return m_angle;
}
void SimpleGLWindow::setAngle(const qreal &angle)
{
m_angle = angle;
this->update();
}
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