一、3D坐标系

记住V_clip = M_projection * M_view * M_model * V_local就行，可以在顶点着色器里面添加位置信息：

#version 330 core
layout (location = 2) in vec3 aPos;//location属性位置有16个
layout (location = 3) in vec3 aColor;
layout (location = 1) in vec2 aTextureCoordinates;
out vec3 ourColor;
out vec2 TextureCoordinates;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
void main()
{gl_Position = projection * view * model * vec4(aPos, 1.0);ourColor = aColor;TextureCoordinates = aTextureCoordinates;
}

片段着色器不用改变：

#version 330 core
out vec4 FragColor;
in vec3 ourColor;
in vec2 TextureCoordinates;
uniform sampler2D textureWall;
uniform sampler2D textureLe;
uniform sampler2D textureSmall;
uniform sampler2D texturePJ;
uniform float ratio;
void main()
{FragColor = mix(texture(textureWall, TextureCoordinates), texture(textureLe, TextureCoordinates), ratio);
}

二、透视投影

这方面可以恶补下线性代数知识。

三、代码实现

3.1 构建一个正方体的点

        在OpenGL里面，三角形是基础图形，正方体6个面，每一个面都是两个三角形拼接而成，所以点需要2×3×6=36个顶点坐标，在坐标的数组里面可以放入颜色、纹理等信息，后面调用解析的时候注意步长和位置即可。

        在编写顶点的时候，只要能连起来是个正方体即可，不同的点做原点都可以，但是一定要连起来，纹理是2个数来表示X和Y，和顶点坐标没有关系。下面是构建的一个例子：

float vertices[] =
{//positions //texture coordinates//正面-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,//背面-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,//左面-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,//右面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,//上面-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,//下面-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
};

3.2 画出正方体

注意要给M_projection * M_view * M_model这三个矩阵，写在外面也可以，但是多个3D图形的话model需要初始化，不然除了第一次的图形是单位矩阵，for循环后面的都不是。

void OpenGLWidget::paintGL()
{QMatrix4x4 model;QMatrix4x4 view;QMatrix4x4 projection;unsigned int time = QTime::currentTime().msec();//先旋转再位移，图片在固定位置旋转//先位移再旋转，图片围着一个地方转//具体参考线性代数矩阵知识
//    model.rotate(time, 1.0f, 5.0f, 0.5f);//旋转view.translate(0.0, 0.0, -3);projection.perspective(45, (float)width()/height(), 0.1, 100);m_shaderProgram.setUniformValue("projection", projection);//red：0.0f无色，1.0f全红glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glEnable(GL_DEPTH_TEST);//加了立方体可以封面glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);m_shaderProgram.bind();//绑定可以理解为使用它m_shaderProgram.setUniformValue("ratio", ratio);glBindVertexArray(VAO);switch (m_shape){case Rect://纹理绑定textureLe->bind(1);textureWall->bind(0);//图形绘画//画之前设置3D图形//V_clip = M_projection * M_view * M_model * V_localm_shaderProgram.setUniformValue("view", view);foreach(auto item, cubePositions){model.setToIdentity();//初始化model.translate(item);//位移model.rotate(time, 1.0f, 5.0f, 0.5f);//旋转m_shaderProgram.setUniformValue("model", model);glDrawArrays(GL_TRIANGLES, 0, 36);}break;default:break;}
}

3.3 完整代码

#include "openglwidget.h"unsigned int VBO, VAO, EBO;
float ratio = 0.5;
float vertices[] =
{//positions //texture coordinates//正面-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,//背面-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,//左面-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,//右面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,//上面-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,//下面-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
};unsigned int indices[] = //note that we start from 0!
{0, 1, 3,//第一个三角形1, 2, 3 // 第二个三角形
};//多个3D图形，建立位移数组
QVector<QVector3D> cubePositions =
{//X,Y,ZQVector3D(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)
};OpenGLWidget::OpenGLWidget(QWidget* parent) : QOpenGLWidget(parent)
{setFocusPolicy(Qt::StrongFocus);m_timer = new QTimer;m_timer->start(100);connect(m_timer, &QTimer::timeout, this, [=](){update();});
}OpenGLWidget::~OpenGLWidget()
{makeCurrent();glDeleteBuffers(1,&VBO);glDeleteBuffers(1, &EBO);glDeleteVertexArrays(1,&VAO);doneCurrent();
}void OpenGLWidget::drawShape(Shape shape)
{m_shape = shape;update();
}void OpenGLWidget::setWireframe(bool wireframe)
{makeCurrent();if (wireframe){glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);}else{glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);}update();doneCurrent();
}void OpenGLWidget::initializeGL()
{initializeOpenGLFunctions();//使用QT封装的着色器bool success;m_shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, ":/shaders/shapes.vert");//顶点着色器m_shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, ":/shaders/shapes.frag");//片段着色器success = m_shaderProgram.link();//连接到着色器if(!success)qDebug() << "ERR:" << m_shaderProgram.log();//创建VBO和VAO对象，并赋予IDglGenVertexArrays(1, &VAO);glGenBuffers(1, &VBO);//绑定VBO和VAO对象glBindVertexArray(VAO);glBindBuffer(GL_ARRAY_BUFFER, VBO);//为当前绑定到target的缓冲区对象创建一个新的数据存储//如果data不是NULL，则使用来自此指针的数据初始化数据存储glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);//访问着色器里面属性的位置m_shaderProgram.bind();GLint posLocation = m_shaderProgram.attributeLocation("aPos");//询问着色器里面变量aPos顶点信息的属性位置GLint textureLocation = m_shaderProgram.attributeLocation("aTextureCoordinates");//告知显卡如何解析缓冲里的顶点属性值glVertexAttribPointer(posLocation, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);//告知显卡如何解析缓冲里的纹理属性值glVertexAttribPointer(textureLocation, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));//开启VAO管理的顶点属性值glEnableVertexAttribArray(posLocation);//开启VAO管理的纹理属性值glEnableVertexAttribArray(textureLocation);//EBO创建与绑定glGenBuffers(1, &EBO);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);//纹理textureWall = new QOpenGLTexture(QImage(":/imags/imag/1.jpg").mirrored());textureLe = new QOpenGLTexture(QImage(":/imags/imag/2.jpg").mirrored());textureSmall = new QOpenGLTexture(QImage(":/imags/imag/3.jpg").mirrored());texturePJ = new QOpenGLTexture(QImage(":/imags/imag/4.jpg").mirrored());//设置纹理单元,纹理单元有16个m_shaderProgram.bind();m_shaderProgram.setUniformValue("textureWall", 0);m_shaderProgram.setUniformValue("textureLe", 1);m_shaderProgram.setUniformValue("textureSmall", 2);m_shaderProgram.setUniformValue("texturePJ", 3);//设置渐远纹理texturePJ->generateMipMaps();//纹理绑定textureLe->bind(1);textureWall->bind(0);//VAO和VBO绑定为0，相当于释放休息glBindBuffer(GL_ARRAY_BUFFER, 0);glBindVertexArray(0);QMatrix4x4 projection;projection.perspective(45, (float)width()/height(), 0.1, 100);m_shaderProgram.setUniformValue("projection", projection);
}void OpenGLWidget::resizeGL(int w, int h)
{Q_UNUSED(h)Q_UNUSED(w)
}void OpenGLWidget::paintGL()
{QMatrix4x4 model;QMatrix4x4 view;unsigned int time = QTime::currentTime().msec();//先旋转再位移，图片在固定位置旋转//先位移再旋转，图片围着一个地方转//具体参考线性代数矩阵知识
//    model.rotate(time, 1.0f, 5.0f, 0.5f);//旋转view.translate(0.0, 0.0, -3);//red：0.0f无色，1.0f全红glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glEnable(GL_DEPTH_TEST);//加了立方体可以封面glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);m_shaderProgram.bind();//绑定可以理解为使用它m_shaderProgram.setUniformValue("ratio", ratio);glBindVertexArray(VAO);switch (m_shape){case Rect://纹理绑定textureLe->bind(1);textureWall->bind(0);//图形绘画//画之前设置3D图形//V_clip = M_projection * M_view * M_model * V_localm_shaderProgram.setUniformValue("view", view);foreach(auto item, cubePositions){model.setToIdentity();//初始化model.translate(item);//位移model.rotate(time, 1.0f, 5.0f, 0.5f);//旋转m_shaderProgram.setUniformValue("model", model);glDrawArrays(GL_TRIANGLES, 0, 36);}break;default:break;}
}void OpenGLWidget::keyPressEvent(QKeyEvent *event)
{switch (event->key()){case Qt::Key_Up:ratio += 0.1;break;case Qt::Key_Down:ratio -= 0.1;break;default:break;}if(ratio>1) ratio = 1;if(ratio<0) ratio = 0;m_shaderProgram.bind();m_shaderProgram.setUniformValue("ratio", ratio);update();
}

详细代码看压缩文件。

3.4 学习地址

5-3代码实现3D效果_哔哩哔哩_bilibili

四、效果展示