初始化

GLFWwindow* initGL(void) {
    //初始化
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    GLFWwindow* window = glfwCreateWindow(600, 600, "OSC_XY", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return NULL;
    }
    //绑定上下文
    glfwMakeContextCurrent(window);
    //根据窗口动态调整视口的大小
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return NULL;
    }
    //允许Debug调试信息查看
    glEnable(GL_DEBUG_OUTPUT);
    glDebugMessageCallback(MessageCallback, 0);
    return window;
} 
//视口跟随窗口调整回调函数
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

参数设置

每帧采样数据量（点）nSamples
采样间隔sampleRate
XY数据数组 x_data[nSamples] y_data[nSamples]
XY总数据量 scratchBuffer[4nSamples+4nSamples]：一个坐标点横纵轴共分裂为4个点，组成一个正方形

Render::Render(int sampleRate, int nSamples, int lineSize, int width, int height) {
    this->nSamples = nSamples;
    this->lineSize = lineSize;
    this->sampleRate = sampleRate;
    this->width = width;
    this->height = height;
    this->x_data = new float[nSamples];
    this->y_data = new float[nSamples];
    this->scratchBuffer = new float[nSamples * 8]();
    this->quadIndex = makeQuadIndex();
    this->vertexIndex = makeVertexIndex(); //顶点索引
    //绘制纹理，暂时不用
    this->outQuadArray = makeOutQuad();
    //暂时没用
    if (makeFrameBuffer() != 0) {
        io.Err("Can Not Make FrameBuffers");
        return;
    }
    else {
        io.Log("FrameBuffers Generated!!!");
    }
    if (this->lineVao == 0 || this->textureVao == 0 ) {
        glGenVertexArrays(1, &this->lineVao);
        glGenVertexArrays(1, &this->textureVao);
    }
    return;
}

正方形顶点索引 quadIndex ：每一个Y轴坐标被拆分成4个顶点，顶点坐标索引nSamples*4 VBO

unsigned int Render::makeQuadIndex() {
    int len = this->nSamples * 4;
    if (len < 0) {
        return -1; 
    }
    short* index = new short[len];
    for (int i = len; i--;) {
        index[i] = i;
    }
    unsigned int vbo;
    glGenBuffers(1, &vbo);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(short)* len, index, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, NULL);
    return vbo;
}

正方形绘制索引 vertexIndex: 每一个Y轴坐标被拆分成4个顶点，组成一个正方形，一个正方形被分隔为两个三角形，总共EBO的索引为nSamples*6 EBO

unsigned int Render::makeVertexIndex() {
    //-1是因为WebGL中会闪屏，最后一个点
    int len = (this->nSamples-1) * 2 * 3;
    if (len < 6) {
        return -1;
    }
    unsigned short* index = new unsigned short[len];
    for (int i = 0, pos = 0; i < len;) {
        index[i++] = pos;
        index[i++] = pos + 2;
        index[i++] = pos + 1;
        index[i++] = pos + 1;
        index[i++] = pos + 2;
        index[i++] = pos + 3;
        pos += 4;
    }
    unsigned int ebo;
    glGenBuffers(1, &ebo);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(unsigned short)*len, index, GL_STATIC_DRAW);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, NULL);
    return ebo;
}

生成正弦波数据

float* IO::genDatas(string anxi, int len) {
    if (len <= 0)
    {
        return new float[1]{-1};
    }
    float* wfm = new float[len];
    if (anxi.compare("x"))
    {
        for (int i = 0; i < len; i++) {
            wfm[i] = sin(i / 200.0);
        }
    }
    else {
        for (int i = 0; i < len; i++) {
            wfm[i] = cos(i / 1000.0);
        }
    }
    return wfm;
}