OpenGL: Study Notes 4 - Vertex Shader 顶点着色器的使用

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## 目标: - 使用顶点着色器对三角形向右平移0.8个单位 ## 顶点着色器 ```cpp // 顶点着色器 const char* vertexShaderSource = "#version 400 core\n" "layout (location=0) in vec3 aPos;\n" "void main()\n" "{\n" "gl_Position= vec4(aPos.x+0.8, aPos.y, aPos.z, 1.0f);\n" "}\n\0"; ``` ## 初始化顶点着色器 ```cpp // 创建vertex着色器对象 int vertexShader = glCreateShader(GL_VERTEX_SHADER); // 将源码字符串赋予着色器对象 glShaderSource(vertexShader, 1, &vertexShaderSource, NULL); // 编译着色器 glCompileShader(vertexShader); ... // 将编译好的着色器对象附加到程序对象上 glAttachShader(shaderProgram, vertexShader); ``` ## 示例程序 ```cpp // glad must put befor GLFW #include #include #include 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; float vertices[] = { -0.5f, -0.5f, 0.0f, //left 0.5f, -0.5f, 0.0f, //right 0.0f, 0.5f, 0.0f //top }; GLFWwindow* window; int init(); void VOASet(); // 片段着色器 // 将着色器源码存入字符串 const char* fragmentShaderSource = "#version 400 core\n" "out vec4 FragColor;\n" "void main()\n" "{\n" "FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n" "}\n\0"; // 顶点着色器 const char* vertexShaderSource = "#version 400 core\n" "layout (location=0) in vec3 aPos;\n" "void main()\n" "{\n" "gl_Position= vec4(aPos.x+0.8, aPos.y, aPos.z, 1.0f);\n" "}\n\0"; int main() { init(); // draw triangle VOASet(); std::cout << "----------------------------------------------------" << std::endl; std::cout << "Create vertex shader " << std::endl; // 创建vertex着色器对象 int vertexShader = glCreateShader(GL_VERTEX_SHADER); // 将源码字符串赋予着色器对象 glShaderSource(vertexShader, 1, &vertexShaderSource, NULL); // 编译着色器 glCompileShader(vertexShader); std::cout << "----------------------------------------------------" << std::endl; std::cout << "Create Fragment shader " << std::endl; // 创建fragment着色器对象 int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER); // 将源码字符串赋予着色器对象 glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL); // 编译着色器 glCompileShader(fragmentShader); std::cout << "----------------------------------------------------" << std::endl; std::cout << "Create shader program" << std::endl; // 创建着色器程序对象 int shaderProgram = glCreateProgram(); // 将编译好的着色器对象附加到程序对象上 glAttachShader(shaderProgram, vertexShader); glAttachShader(shaderProgram, fragmentShader); // 链接生成着色器程序 glLinkProgram(shaderProgram); // render loop // ----------- while (!glfwWindowShouldClose(window)) { // input // ----- processInput(window); // render // ------ glClearColor(0.2f, 0.3f, 0.3f, 1.0f); glClear(GL_COLOR_BUFFER_BIT); // Use customized shader // 使用自定义的着色器程序 glUseProgram(shaderProgram); // Draw triangle glDrawArrays(GL_TRIANGLES, 0, 3); // VBO 0->3 // 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; } //输入处理函数 // 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); } //窗口大小设置回调函数 // 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); } int init() { //设置OpenGL版本等信息 // 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 // -------------------- window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "OpenGLExample", NULL, NULL); if (window == NULL) { std::cout << "Failed to create GLFW window" << std::endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); //把OpenGL的函数指针导入给GLAD // glad: load all OpenGL function pointers // --------------------------------------- if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { std::cout << "Failed to initialize GLAD" << std::endl; return -1; } } void VOASet() { // ID unsigned int VBO, VAO; // 生成VAO glGenVertexArrays(1, &VAO); // 生成VBO glGenBuffers(1, &VBO); // 绑定VAO & VBO glBindVertexArray(VAO); // 指定这是一个VBO buffer,因为buffer的各类有很多种 glBindBuffer(GL_ARRAY_BUFFER, VBO); // 开辟显存空间 // p1: 目标, p1: 写多少数据, p3: 写什么内容, p4: 表示以后不修改 glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); // 告诉显卡值的结构 glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0); glEnableVertexAttribArray(0); } ``` ## 结果

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