17. OPenGL实现旋转移动物体

1. 说明：

整体思路：如果想实现动态，可以使用一个矩阵和我们给定的坐标值进行相乘，实时的改变坐标值
类似于坐标的齐次变换，然后使用一个定时器，在规定时间内触发重新绘制的函数。
实际效果：

OPenGL移动旋转图形

2. 实现步骤：

第一步：
在MyOpenGLWidget.h文件中添加一个定时器变量，用来实时的调用更新函数，让画布在规定的间隔时间内重绘：

#ifndef MYOPENGLWIDGET_H
#define MYOPENGLWIDGET_H#include <QObject>
#include <QWidget>
#include <QTimer>
#include <QTime>#include <QOpenGLWidget>
#include <QOpenGLFunctions_3_3_Core>
#include <QOpenGLShaderProgram>
#include <QOpenGLTexture>class MyOpenGLWidget : public QOpenGLWidget,QOpenGLFunctions_3_3_Core
{Q_OBJECT
public:enum Shape{None,Rect,Circle,Triangle};explicit MyOpenGLWidget(QWidget *parent = nullptr);void drawShape(Shape shape);void clearGraphic();void setWireFrame(bool wireFrame);protected:virtual void initializeGL() override;virtual void resizeGL(int w, int h) override;virtual void paintGL() override;signals:public slots:void on_timeout();private:Shape m_shape;QOpenGLShaderProgram shaderProgram;QOpenGLTexture *textureStar;QTimer timer;	//在之前的基础上再添加一个 定时器 变量
};
#endif // MYOPENGLWIDGET_H

第二步：
在MyOpenGLWidget.cpp文件中的paintGL()函数内部声明一个矩阵，使这个矩阵位移一段距离，然后随着时间不停的做旋转，最后将这个矩阵作用在顶点着色器的位置坐标上，即可实现物体的平移和旋转。
注意：矩阵要用左乘，且矩阵matrix在代码的体现上应该先平移，再旋转，否则会乱掉
paintGL()函数代码如下:

void MyOpenGLWidget::paintGL()
{QMatrix4x4 matrix;unsigned int time = QTime::currentTime().msec();matrix.translate(0.5,-0.5,0.0);//先写平移的代码matrix.rotate(time,0.0f,0.0f,1.0f);//再写旋转的代码glClearColor(0.5f,0.9f,0.4f,1.0f);glClear(GL_COLOR_BUFFER_BIT);shaderProgram.bind();textureStar->bind(0);//在渲染前只需开启对应的VAO即可glBindVertexArray(VAO);switch (m_shape) {case Rect://将变量matrix传输到顶点着色器中的变量theMatrix中shaderProgram.setUniformValue("theMatrix",matrix);glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,&indices);break;default:break;}}

第三步：
在顶点着色器文件中，定义变量theMatrix，用来接收来自外界数据的传入(matrix)，并将变量theMatrix作用在顶点位置坐标上，注意是左乘，代码如下：

#version 330 corelayout(location = 0) in vec3 aPos;
layout(location = 1) in vec3 aColor;
layout(location = 2) in vec2 aTexCord;out vec3 ourColor;
out vec2 texCord;uniform mat4 theMatrix;//定义变量，接收外界数据void main()
{//将矩阵变换作用在位置坐标上gl_Position = theMatrix * vec4(aPos.x,aPos.y,aPos.z,1.0f);ourColor = aColor;texCord = aTexCord;
}

MyOpenGLWidget.cpp整天代码：

#include "myopenglwidget.h"unsigned int VBO,VAO;//添加一个索引控制器
unsigned int EBO;float vertices[] = {-0.5f,-0.5f,0.0f,0.5f,-0.5f,0.0f,0.0f,0.5f,0.0f
};float verticesColorTexture[] = {	//每一行数据的前三个是位置坐标，后三个是颜色值0.5f,0.5f,0.5f,1.0f,0.0f,0.0f,1.0f,1.0f,0.5f,-0.5f,0.0f,0.0f,1.0f,0.0f,1.0f,0.0f,-0.5f,-0.5f,0.0f,0.0f,0.0f,1.0f,0.0f,0.0f,-0.5f,0.5f,0.0f,0.5f,0.5f,0.5f,0.0f,1.0f
};//添加索引数据
unsigned int indices[]={0,1,3,1,2,3
};MyOpenGLWidget::MyOpenGLWidget(QWidget *parent) :  QOpenGLWidget(parent)
{connect(&timer,SIGNAL(timeout()),this,SLOT(on_timeout()));//定时器触发连接槽函数timer.start(100);//启动定时器
}void MyOpenGLWidget::drawShape(MyOpenGLWidget::Shape shape)
{makeCurrent();m_shape = shape;update();doneCurrent();
}void MyOpenGLWidget::clearGraphic()
{makeCurrent();drawShape(MyOpenGLWidget::None);makeCurrent();glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);update();doneCurrent();
}void MyOpenGLWidget::setWireFrame(bool wireFrame)
{makeCurrent();if(wireFrame){glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);}else{glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);}update();doneCurrent();
}void MyOpenGLWidget::initializeGL()
{initializeOpenGLFunctions();//void glGenVertexArrays(GLsizei n, GLuint *arrays)生成顶点数组对象名称// n: 要产生的VAO对象的数量// arrays: 存放产生的VAO对象的名称glGenVertexArrays(1,&VAO);// void glGenBuffers(GLsizei n,GLuint *buffers)生成顶点缓冲对象// n: 要产生的VBO对象的数量// arrays: 存放产生的VBO对象的名称glGenBuffers(1,&VBO);//初始化索引器glGenBuffers(1,&EBO);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof (indices),indices,GL_STATIC_DRAW);//绑定VAO和VBOglBindVertexArray(VAO);glBindBuffer(GL_ARRAY_BUFFER,VBO);//在VBO中存入顶点数据glBufferData(GL_ARRAY_BUFFER,sizeof (verticesColorTexture),verticesColorTexture,GL_STATIC_DRAW);//告诉VAO怎么在VBO中拿数据(顶点位置数据)glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,8*sizeof (float),(void*)0);//开启第一个VAOglEnableVertexAttribArray(0);//告诉VAO怎么在VBO中拿数据(颜色数据)glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,8*sizeof (float),(void*)(3*sizeof(float)));//开启第二个VAOglEnableVertexAttribArray(1);//告诉VAO怎么在VBO中拿数据(纹理数据)glVertexAttribPointer(2,2,GL_FLOAT,GL_FALSE,8*sizeof (float),(void*)(6*sizeof(float)));//开启第三个VAOglEnableVertexAttribArray(2);//用完之后解除绑定(信息已经被记录下来了)glBindBuffer(GL_ARRAY_BUFFER,0);glBindVertexArray(0);//添加着色器shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex,":/shaders/Shaders/shape.vert");shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment,":/shaders/Shaders/shape.frag");shaderProgram.link();//添加纹理数据textureStar = new QOpenGLTexture(QImage(":/img/images/water.jpg").mirrored());shaderProgram.setUniformValue("textureStar",0);
}void MyOpenGLWidget::resizeGL(int w, int h)
{Q_UNUSED(w);Q_UNUSED(h);}void MyOpenGLWidget::paintGL()
{QMatrix4x4 matrix;unsigned int time = QTime::currentTime().msec();matrix.translate(0.5,-0.5,0.0);matrix.rotate(time,0.0f,0.0f,1.0f);glClearColor(0.5f,0.9f,0.4f,1.0f);glClear(GL_COLOR_BUFFER_BIT);shaderProgram.bind();textureStar->bind(0);//在渲染前只需开启对应的VAO即可glBindVertexArray(VAO);switch (m_shape) {case Rect:shaderProgram.setUniformValue("theMatrix",matrix);glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,&indices);break;default:break;}}
//定时器槽函数内，调用opengl的更新函数
void MyOpenGLWidget::on_timeout()
{update();
}

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