參考資料：https://learnopengl-cn.github.io/01%20Getting%20started/05%20Shaders/

著色器基本描述

首先看一個著色器

#version version_numberlayout (location = 0) in type in_variable_name; layout (location = 1) in type in_variable_name; out type out_variable_name; uniform type uniform_name;int main() {// 處理輸入并進行一些圖形操作...// 輸出處理過的結果到輸出變量out_variable_name = weird_stuff_we_processed; }

第一行代碼表示著色器版本 ，2-4行是變量。

看2-3行代碼

layout (location = 0) in type in_variable_name; layout (location = 1) in type in_variable_name;

表示輸入變量，其中location的值是用來判斷將讀入的數據送到那個變量中。著色器的不同變量可以存儲不同屬性。
配合以下兩行代碼實現功能：

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0); glEnableVertexAttribArray(0);//屬性值

看第4行代碼

作用是輸出頂點著色器程序結果

out type out_variable_name;

看第5行代碼

uniform type uniform_name;

是一個全局變量，想調用是可以通過以下語句：

int vertexColorLocation = glGetUniformLocation(shaderProgram, "uniform_name"); glUseProgram(shaderProgram); glUniform1f (vertexColorLocation, 0.5f);

其他就是主函數，注意這個程序的語言是GLSL

著色器程序

• 著色器程序按順序組裝著色器，并且連接它們。前面著色其輸出是后面著色器的輸入，通過同樣的變量名聯系。

// link shadersint shaderProgram = glCreateProgram();glAttachShader(shaderProgram, vertexShader);glAttachShader(shaderProgram, fragmentShader);glLinkProgram(shaderProgram);

完整的程序

#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;//著色器頂點程序 const char *vertexShaderSource = "#version 330 core\n" "layout (location = 0) in vec3 aPos;\n" "layout (location = 1) in vec3 aColor;\n" "uniform float x_move ;\n" "out vec3 ourColor;\n" "void main()\n" "{\n" " gl_Position = vec4(aPos.x - x_move, aPos.y, aPos.z, 1.0);\n" //" gl_Position = vec4(-aPos, 1.0);\n" 讓三角形上下顛倒 " ourColor = aColor;\n" "}\0"; //著色器片段程序 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() {// 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); // uncomment this statement to fix compilation on OS X #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;}// build and compile our shader program// ------------------------------------// 創建頂點著色器int vertexShader = glCreateShader(GL_VERTEX_SHADER);glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);glCompileShader(vertexShader);// check for shader compile errorsint 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;}// 創建片段著色器int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);glCompileShader(fragmentShader);// check for shader compile errorsglGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);if (!success){glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;}// 連接著色器生成著色器程序int shaderProgram = glCreateProgram();glAttachShader(shaderProgram, vertexShader);glAttachShader(shaderProgram, fragmentShader);glLinkProgram(shaderProgram);// check for linking errorsglGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);if (!success) {glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;}glDeleteShader(vertexShader);glDeleteShader(fragmentShader);// 頂點位置和顏色屬性// ------------------------------------------------------------------float vertices[] = {// positions // colors0.5f, -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 left0.0f, 0.5f, 0.0f, 0.0f, 0.0f, 1.0f // top };//生成頂點數據VBO和頂點數組屬性VAOunsigned int VBO, VAO;glGenVertexArrays(1, &VAO);glGenBuffers(1, &VBO);// 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);// position attributeglVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);// color attributeglVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));glEnableVertexAttribArray(1);// 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);// as we only have a single shader, we could also just activate our shader once beforehand if we want to glUseProgram(shaderProgram);// render loop// -----------while (!glfwWindowShouldClose(window)){// input// -----processInput(window);// render// ------glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);//給著色器中全局變量復制int vertexColorLocation = glGetUniformLocation(shaderProgram, "x_move");glUseProgram(shaderProgram);glUniform1f (vertexColorLocation, 0.5f);// render the triangleglBindVertexArray(VAO);glDrawArrays(GL_TRIANGLES, 0, 3);// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)// -------------------------------------------------------------------------------glfwSwapBuffers(window);glfwPollEvents();}// optional: de-allocate all resources once they've outlived their purpose:// ------------------------------------------------------------------------glDeleteVertexArrays(1, &VAO);glDeleteBuffers(1, &VBO);// 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); }

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