OpenGL学习笔记（五）着色器

下面是个例子利用着色器绘制彩色三角形

//
// Created by czh on 6/26/18.
//

#include 
#include 
#include 
#include 

void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;


const char *vertexShaderSource ="#version 330 core\n"
        "layout (location = 0) in vec3 aPos;\n"
        "layout (location = 1) in vec3 aColor;\n"
        "out vec3 ourColor;\n"
        "void main()\n"
        "{\n"
        "   gl_Position = vec4(aPos, 1.0);\n"
        "   ourColor = aColor;\n"
        "}\0";

const char *fragmentShaderSource = "#version 330 core\n"
        "out vec4 FragColor;\n"
        "in vec3 ourColor;\n"
        "void main()\n"
        "{\n"
        "   FragColor = vec4(ourColor, 1.0f);\n"
        "}\n\0";

int main()
{
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "chicken", NULL, NULL);
    if (window == NULL)
    {
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        glfwTerminate();
        return -1;
    }

    int vertexShader = glCreateShader(GL_VERTEX_SHADER);//创建顶点着色器
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);//附加到着色器对象上
    glCompileShader(vertexShader);//编译着色器对象

    int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);//创建片段着色器
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);//附加到着色器对象上
    glCompileShader(fragmentShader);//编译着色器对象

    //链接着色器对象
    int shaderProgram = glCreateProgram();//创建一个程序对象
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);
    //删除着色器对象，我们不再需要它们
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    float vertices[] = {
            // 位置              // 颜色
            0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,   // 右下
            -0.5f, -0.5f, 0.0f,  0.0f, 1.0f, 0.0f,   // 左下
            0.0f,  0.5f, 0.0f,  0.0f, 0.0f, 1.0f    // 顶部
    };

    unsigned int VAO, VBO;//顶点数组对象Vertex Array Object\顶点缓冲对象Vertex Buffer Object\索引缓冲对象Element Buffer Object
    glGenVertexArrays(1, &VAO);//创建一个顶点数组对象
    glGenBuffers(1, &VBO);//生成一个顶点缓冲对象

    glBindVertexArray(VAO);//1.绑定顶点数组对象
    glBindBuffer(GL_ARRAY_BUFFER, VBO);//2.把新创建的顶点数组绑定到缓冲中
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    //GL_STATIC_DRAW ：数据不会或几乎不会改变。
    //GL_DYNAMIC_DRAW：数据会被改变很多。
    //GL_STREAM_DRAW ：数据每次绘制时都会改变。

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);//４.设置顶点属性指针
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));//４.设置顶点属性指针
    glEnableVertexAttribArray(1);
    //glBindBuffer(GL_ARRAY_BUFFER, 0);

    glUseProgram(shaderProgram);//５绘制物体

    while (!glfwWindowShouldClose(window))
    {
        processInput(window);


        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);



        glBindVertexArray(VAO);
        glDrawArrays(GL_TRIANGLES, 0, 3);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);

    glfwTerminate();
    return 0;
}

// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow *window)
{
    if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);
}

// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    // make sure the viewport matches the new window dimensions; note that width and
    // height will be significantly larger than specified on retina displays.
    glViewport(0, 0, width, height);
}