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OpenGL

现代OpenGL保姆级课程(bilibili)

现代 OpenGL 保姆级教程(github)

最好的OpenGL教程之一

OpenGL + Qt

检测OpenGL版本

相关参考资源

sample

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#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

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

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

int main()
{
    // glfw: initialize and configure
    // ------------------------------
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

    // glfw window creation
    // --------------------
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
    if (window == NULL)
    {
        std::cout << "Failed to create GLFW window" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

    // glad: load all OpenGL function pointers
    // ---------------------------------------
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        return -1;
    }    

    // render loop
    // -----------
    while (!glfwWindowShouldClose(window))
    {
        // input
        // -----
        processInput(window);

        // render
        // ------
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    // glfw: terminate, clearing all previously allocated GLFW resources.
    // ------------------------------------------------------------------
    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);
}

glfw: initialize and configure

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// glfw: initialize and configure
// ------------------------------
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

glfw window creation

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// glfw window creation
// --------------------
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
    std::cout << "Failed to create GLFW window" << std::endl;
    glfwTerminate();
    return -1;
}
glfwMakeContextCurrent(window);

GLAD

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if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
    std::cout << "Failed to initialize GLAD" << std::endl;
    return -1;
}

Rendering

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// render loop
while(!glfwWindowShouldClose(window))
{
    // input
    processInput(window);

    // rendering commands here
    ...

    // check and call events and swap the buffers
    glfwPollEvents();
    glfwSwapBuffers(window);
}

build and compile our shader program

vertex shader

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// ------------------------------------
// vertex shader
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// check for shader compile errors
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
    glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}

fragment shader

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// fragment shader
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// check for shader compile errors
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
    glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}

link shaders

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// link shaders
unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
// check for linking errors
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
    glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
    std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}

delete shader

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glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);

Hello Triangle

Vertex input

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float vertices[] = {
    -0.5f, -0.5f, 0.0f,
     0.5f, -0.5f, 0.0f,
     0.0f,  0.5f, 0.0f
};

set up vertex data

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// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
float vertices[] = {
     0.5f,  0.5f, 0.0f,  // top right
     0.5f, -0.5f, 0.0f,  // bottom right
    -0.5f, -0.5f, 0.0f,  // bottom left
    -0.5f,  0.5f, 0.0f   // top left 
};
unsigned int indices[] = {  // note that we start from 0!
    0, 1, 3,  // first Triangle
    1, 2, 3   // second Triangle
};
unsigned int VBO, VAO, EBO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glGenBuffers(1, &EBO);
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
glBindVertexArray(VAO);

glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);

// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
glBindBuffer(GL_ARRAY_BUFFER, 0); 

// remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
//glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
glBindVertexArray(0);

two triangles setup

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// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
float firstTriangle[] = {
    -0.9f, -0.5f, 0.0f,  // left 
    -0.0f, -0.5f, 0.0f,  // right
    -0.45f, 0.5f, 0.0f,  // top 
};
float secondTriangle[] = {
    0.0f, -0.5f, 0.0f,  // left
    0.9f, -0.5f, 0.0f,  // right
    0.45f, 0.5f, 0.0f   // top 
};
unsigned int VBOs[2], VAOs[2];
glGenVertexArrays(2, VAOs); // we can also generate multiple VAOs or buffers at the same time
glGenBuffers(2, VBOs);
// first triangle setup
// --------------------
glBindVertexArray(VAOs[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(firstTriangle), firstTriangle, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);   // Vertex attributes stay the same
glEnableVertexAttribArray(0);
// glBindVertexArray(0); // no need to unbind at all as we directly bind a different VAO the next few lines
// second triangle setup
// ---------------------
glBindVertexArray(VAOs[1]); // note that we bind to a different VAO now
glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]); // and a different VBO
glBufferData(GL_ARRAY_BUFFER, sizeof(secondTriangle), secondTriangle, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0); // because the vertex data is tightly packed we can also specify 0 as the vertex attribute's stride to let OpenGL figure it out
glEnableVertexAttribArray(0);
// glBindVertexArray(0); // not really necessary as well, but beware of calls that could affect VAOs while this one is bound (like binding element buffer objects, or enabling/disabling vertex attributes)

draw two triangles

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// draw first triangle using the data from the first VAO
glBindVertexArray(VAOs[0]);
glDrawArrays(GL_TRIANGLES, 0, 3);
// then we draw the second triangle using the data from the second VAO
glBindVertexArray(VAOs[1]);
glDrawArrays(GL_TRIANGLES, 0, 3);

de-allocate all resources

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// optional: de-allocate all resources once they've outlived their purpose:
// ------------------------------------------------------------------------
glDeleteVertexArrays(2, VAOs);
glDeleteBuffers(2, VBOs);
glDeleteProgram(shaderProgram);

two shader programs

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const char *vertexShaderSource = "#version 330 core\n"
    "layout (location = 0) in vec3 aPos;\n"
    "void main()\n"
    "{\n"
    "   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
    "}\0";
const char *fragmentShader1Source = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "void main()\n"
    "{\n"
    "   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
    "}\n\0";
const char *fragmentShader2Source = "#version 330 core\n"
    "out vec4 FragColor;\n"
    "void main()\n"
    "{\n"
    "   FragColor = vec4(1.0f, 1.0f, 0.0f, 1.0f);\n"
    "}\n\0";

build and compile our shader program

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// build and compile our shader program
    // ------------------------------------
    // we skipped compile log checks this time for readability (if you do encounter issues, add the compile-checks! see previous code samples)
    unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
    unsigned int fragmentShaderOrange = glCreateShader(GL_FRAGMENT_SHADER); // the first fragment shader that outputs the color orange
    unsigned int fragmentShaderYellow = glCreateShader(GL_FRAGMENT_SHADER); // the second fragment shader that outputs the color yellow
    unsigned int shaderProgramOrange = glCreateProgram();
    unsigned int shaderProgramYellow = glCreateProgram(); // the second shader program
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);
    glShaderSource(fragmentShaderOrange, 1, &fragmentShader1Source, NULL);
    glCompileShader(fragmentShaderOrange);
    glShaderSource(fragmentShaderYellow, 1, &fragmentShader2Source, NULL);
    glCompileShader(fragmentShaderYellow);
    // link the first program object
    glAttachShader(shaderProgramOrange, vertexShader);
    glAttachShader(shaderProgramOrange, fragmentShaderOrange);
    glLinkProgram(shaderProgramOrange);
    // then link the second program object using a different fragment shader (but same vertex shader)
    // this is perfectly allowed since the inputs and outputs of both the vertex and fragment shaders are equally matched.
    glAttachShader(shaderProgramYellow, vertexShader);
    glAttachShader(shaderProgramYellow, fragmentShaderYellow);
    glLinkProgram(shaderProgramYellow);

draw two triangles with different fragment shaders

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// now when we draw the triangle we first use the vertex and orange fragment shader from the first program
    glUseProgram(shaderProgramOrange);
    // draw the first triangle using the data from our first VAO
    glBindVertexArray(VAOs[0]);
    glDrawArrays(GL_TRIANGLES, 0, 3);   // this call should output an orange triangle
    // then we draw the second triangle using the data from the second VAO
    // when we draw the second triangle we want to use a different shader program so we switch to the shader program with our yellow fragment shader.
    glUseProgram(shaderProgramYellow);
    glBindVertexArray(VAOs[1]);
    glDrawArrays(GL_TRIANGLES, 0, 3);   // this call should output a yellow triangle

de-allocate all resources

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// optional: de-allocate all resources once they've outlived their purpose:
    // ------------------------------------------------------------------------
    glDeleteVertexArrays(2, VAOs);
    glDeleteBuffers(2, VBOs);
    glDeleteProgram(shaderProgramOrange);
    glDeleteProgram(shaderProgramYellow);

set up vertex data (and buffer(s)) and configure vertex attributes

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// set up vertex data (and buffer(s)) and configure vertex attributes
    // ------------------------------------------------------------------
    float vertices[] = {
        // positions         // colors
         0.5f, -0.5f, 0.0f,  1.0f, 0.0f, 0.0f,  // bottom right
        -0.5f, -0.5f, 0.0f,  0.0f, 1.0f, 0.0f,  // bottom left
         0.0f,  0.5f, 0.0f,  0.0f, 0.0f, 1.0f   // top 
    };

set up vertex data and texture coords

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   // set up vertex data (and buffer(s)) and configure vertex attributes
    // ------------------------------------------------------------------
    float vertices[] = {
        // positions          // colors           // texture coords
         0.5f,  0.5f, 0.0f,   1.0f, 0.0f, 0.0f,   1.0f, 1.0f, // top right
         0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,   1.0f, 0.0f, // bottom right
        -0.5f, -0.5f, 0.0f,   0.0f, 0.0f, 1.0f,   0.0f, 0.0f, // bottom left
        -0.5f,  0.5f, 0.0f,   1.0f, 1.0f, 0.0f,   0.0f, 1.0f  // top left 
    };
    unsigned int indices[] = {
        0, 1, 3, // first triangle
        1, 2, 3  // second triangle
    };

load image, create texture and generate mipmaps

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 // load image, create texture and generate mipmaps
    int width, height, nrChannels;
    stbi_set_flip_vertically_on_load(true); // tell stb_image.h to flip loaded texture's on the y-axis.
    // The FileSystem::getPath(...) is part of the GitHub repository so we can find files on any IDE/platform; replace it with your own image path.
    unsigned char *data = stbi_load(FileSystem::getPath("resources/textures/container.jpg").c_str(), &width, &height, &nrChannels, 0);
    if (data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
    {
        std::cout << "Failed to load texture" << std::endl;
    }
    stbi_image_free(data);