Qt+OpenGL——参考公开课绘制球

淩亂°似流年 2023-03-01 10:58 15阅读 0赞

公开课地址：[中国大学慕课网——华中科技大学《计算机图形学》][Link 1]

根据老师的课件的代码绘制出来的球只有一面，当把X坐标和Z坐标进行交换就能正常绘制出球。  
shader代码参考上一篇博客：[Qt+OpenGL——索引绘制四边形][Qt_OpenGL]

头文件

#ifndef GLWIDGET_H
    #define GLWIDGET_H
    
    #include <QOpenGLWidget>
    #include <QOpenGLFunctions_4_5_Core>
    
    #include <QOpenGLShaderProgram>
    
    class GLWidget : public QOpenGLWidget,public QOpenGLFunctions_4_5_Core
    {
        
        Q_OBJECT
    public:
        explicit GLWidget(QWidget *parent=nullptr);
        ~GLWidget();
    
    protected:
    
        void iniDatas();
    
        void initializeGL(); //初始化相关的操作全在这个函数中完成
        void resizeGL(int w,int h);
        void paintGL();
    
        float *getBallVertex(int xSegment,int ySegment);
        int *getBallIndices(int xSegment,int ySegment);
    
    private:
        QOpenGLShaderProgram *m_pShaderProgram = nullptr;
    
    };
    
    #endif // GLWIDGET_H

源文件

#include "glwidget.h"
    #include <QOpenGLBuffer>
    #include <QtMath>
    
    #include <QDebug>
    
    
    #define BUFFER_OFFSET(offset) ((void*)(offset))
    
    
    #define BALL_X_SEGMENT 50
    #define BALL_Y_SEGMENT 50
    
    
    GLuint VAO = -1;
    GLWidget::GLWidget(QWidget *parent):
        QOpenGLWidget(parent)
    {
        
    
    }
    
    GLWidget::~GLWidget()
    {
        
    
    }
    
    void GLWidget::iniDatas()
    {
        
    
        float *vertices = getBallVertex(BALL_X_SEGMENT,BALL_Y_SEGMENT);
        int *indices = getBallIndices(BALL_X_SEGMENT,BALL_Y_SEGMENT);
    
        glGenVertexArrays(1,&VAO);
        glBindVertexArray(VAO);
    
        GLuint VBO;
        glGenBuffers(1,&VBO);
        glBindBuffer(GL_ARRAY_BUFFER,VBO);
        glBufferData(GL_ARRAY_BUFFER,sizeof(vertices) * (BALL_X_SEGMENT + 1) * (BALL_Y_SEGMENT + 1) * 3,vertices,GL_STATIC_DRAW);
        glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,sizeof(float) * 3,BUFFER_OFFSET(0));
        glEnableVertexAttribArray(0);
    
        GLuint EBO;
        glGenBuffers(1,&EBO);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices) * BALL_X_SEGMENT * BALL_Y_SEGMENT * 6,indices,GL_STATIC_DRAW);
    
        glBindVertexArray(0);//解绑
        glBindBuffer(GL_ARRAY_BUFFER,0);
    
        //    glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);//填充图,，默认
    //    glPolygonMode(GL_FRONT_AND_BACK,GL_POINT);//散点图
            glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);//线框图
    }
    
    void GLWidget::initializeGL()
    {
        
        initializeOpenGLFunctions();
    
        m_pShaderProgram = new QOpenGLShaderProgram(this);
        m_pShaderProgram->addShaderFromSourceFile(QOpenGLShader::Vertex,":/shaders/vertext.vert");
        m_pShaderProgram->addShaderFromSourceFile(QOpenGLShader::Fragment,":/shaders/fragment.frag");
        m_pShaderProgram->link();
        m_pShaderProgram->bind();
    
        iniDatas();
    }
    
    void GLWidget::resizeGL(int w, int h)
    {
        
        glViewport(0,0,w,h);
    }
    
    void GLWidget::paintGL()
    {
        
        static const GLfloat color[] = {
        0.0f,0.0f,0.0f,1.0f};
    
        glClearBufferfv(GL_COLOR,0,color);
    
        if(VAO == -1){
        
            return;
        }
    
        glUseProgram(m_pShaderProgram->programId());
        glBindVertexArray(VAO);
        glDrawElements(GL_TRIANGLES,(BALL_X_SEGMENT + 1) * (BALL_Y_SEGMENT + 1) * 3 * 6,GL_UNSIGNED_INT,0);
        glBindVertexArray(0);
    
        update();
    }
    
    float *GLWidget::getBallVertex(int xSegment, int ySegment)
    {
        
        float *data = nullptr;
        data = new float[(xSegment + 1) * (ySegment + 1) * 3];
    
        int nIndex = 0;
        for (int y = 0; y <= ySegment; ++y) {
        
            for (int x = 0; x <= xSegment; ++x) {
        
                float xS = x * 1.0 / xSegment;
                float yS = y * 1.0 / ySegment;
    
                float xPos = qSin(xS * 2.0f * M_PI) * qSin(yS * M_PI);
                float yPos = qCos(yS * M_PI);
                float zPos = qCos(xS * 2.0f * M_PI) * qSin(ySegment * M_PI);
    
                data[nIndex] = xPos;
                data[nIndex + 1] = yPos;
                data[nIndex + 2] = zPos;
    
                nIndex += 3;
    
            }
        }
    
        return data;
    }
    
    int *GLWidget::getBallIndices(int xSegment, int ySegment)
    {
        
        int *indices = nullptr;
        indices = new int[xSegment * ySegment * 6];
    
        int nIndex = 0;
        for (int i = 0; i < ySegment; ++i) {
        
            for (int j = 0; j < xSegment; ++j) {
        
    
                indices[nIndex] = i * (xSegment + 1) + j;
                indices[nIndex + 1] = (i + 1) * (xSegment + 1) + j;
                indices[nIndex + 2] = (i + 1) * (xSegment + 1) + (j + 1);
                indices[nIndex + 3] = i * (xSegment + 1) + j;
                indices[nIndex + 4] = (i + 1) * (xSegment + 1) + (j + 1);
                indices[nIndex + 5] = i * (xSegment + 1) + (j + 1);
    
                nIndex += 6;
            }
        }
    
        return indices;
    }

最终效果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0p1aWN5QWN0aXZlR2lsYmVydA_size_16_color_FFFFFF_t_70]

[Link 1]: https://www.icourse163.org/learn/HUST-1003636001?tid=1206895203&from=study#/learn/content?type=detail&id=1211820052
[Qt_OpenGL]: https://blog.csdn.net/JuicyActiveGilbert/article/details/107538735
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0p1aWN5QWN0aXZlR2lsYmVydA_size_16_color_FFFFFF_t_70]: /images/20230208/80d16dfa9c1f438a8dc4717273daf66c.png