OpenGL 繪制 2個不同顏色的三角形

#include <iostream>
// GLEW
#define GLEW_STATIC
#include <GL/glew.h>
// GLFW
#include <GLFW/glfw3.h>
#pragma comment(lib,"opengl32.lib")
#pragma comment(lib,"glu32.lib")

using namespace std;

// 窗口大小
const GLuint WIDTH = 800, HEIGHT = 600;

// 着色器 GLSL
const GLchar* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 position;\n"
"void main()\n"
"{\n"
"gl_Position = vec4(position.x, position.y, position.z, 1.0);\n"
"}\0";
const GLchar* fragmentShaderSource0 = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(0.5f, 0.2f, 1.0f, 1.0f);\n"
"}\n\0";
const GLchar* fragmentShaderSource1 = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.8f, 0.0f, 1.0f);\n"
"}\n\0";

int main(void) {

	// 初始化 GLFW
	glfwInit();
	// glfwWindowHint() // 配置 GLFW 函數（設置的選項，選項的值）
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
	// Mac OS 使用
	// glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

	// 創建一個窗口
	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "FirstTriangle", nullptr, nullptr);
	glfwMakeContextCurrent(window);

	// 初始化 GLEW
	glewExperimental = GL_TRUE;
	glewInit();

	// 設置窗口大小
	int width, height;
	glfwGetFramebufferSize(window, &width, &height);
	glViewport(0, 0, width, height);

	// 配置着色器
	// 創建一個着色器對象（GL_VERTEX_SHADER：頂點着色器）
	GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
	// 把着色器源碼附加到着色器對象上，然后編譯它
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	// 檢測編譯時錯誤，輸出錯誤信息
	GLint success;
	GLchar 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;
	}

	// 創建第1個着色器對象（GL_FRAGMENT_SHADER：片段着色器）
	GLuint fragmentShader0 = glCreateShader(GL_FRAGMENT_SHADER);
	// 着色器源碼附加及編譯
	glShaderSource(fragmentShader0, 1, &fragmentShaderSource0, NULL);
	glCompileShader(fragmentShader0);
	// 檢測編譯時錯誤，輸出錯誤信息
	glGetShaderiv(fragmentShader0, GL_COMPILE_STATUS, &success);
	if (!success){
		glGetShaderInfoLog(fragmentShader0, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// 創建第2個着色器對象（GL_FRAGMENT_SHADER：片段着色器）
	GLuint fragmentShader1 = glCreateShader(GL_FRAGMENT_SHADER);
	// 着色器源碼附加及編譯
	glShaderSource(fragmentShader1, 1, &fragmentShaderSource1, NULL);
	glCompileShader(fragmentShader1);
	// 檢測編譯時錯誤，輸出錯誤信息
	glGetShaderiv(fragmentShader1, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(fragmentShader1, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}

	// 創建 2個着色器程序對象
	GLuint shaderProgram0 = glCreateProgram();
	GLuint shaderProgram1 = glCreateProgram();
	// 鏈接着色器程序
	glAttachShader(shaderProgram0, vertexShader);
	glAttachShader(shaderProgram1, vertexShader);
	glAttachShader(shaderProgram0, fragmentShader0);
	glAttachShader(shaderProgram1, fragmentShader1);
	glLinkProgram(shaderProgram0);
	glLinkProgram(shaderProgram1);
	// 激活對象
	glUseProgram(shaderProgram0);
	// 檢查錯誤，輸出日志
	glGetProgramiv(shaderProgram0, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram0, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}
	glUseProgram(shaderProgram1);
	glGetProgramiv(shaderProgram1, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram1, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}
	// 激活后需要刪除着色器對象
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader0);
	glDeleteShader(fragmentShader1);

	// 輸入頂點數據（這是一個平面的三角形，z 坐標表示深度）
	//GLfloat vertices[] = {
	//	-0.5f, -0.5f, 0.0f,
	//	 0.5f, -0.5f, 0.0f,
	//	 0.0f,  0.5f, 0.0f, };
	// 輸入頂點數據（這是 2個平面的三角形） 
	GLfloat vertices0[] = {
	-0.5f, -0.5f, 0.0f,
	 0.0f,  0.0f, 0.0f,
	-0.3f,  0.3f, 0.0f, };
	GLfloat vertices1[] = {
	 0.5f, -0.5f, 0.0f,
	 0.0f,  0.0f, 0.0f,
	 0.3f,  0.3f, 0.0f, };

	// 生成 2個 VBO 對象
	GLuint VBOs[2];
	glGenBuffers(2, VBOs);
	// 創建 2個 VAO
	GLuint VAOs[2];
	glGenVertexArrays(2, VAOs);

	// 把新創建的緩沖綁定到 GL_ARRAY_BUFFER 目標上
	glBindVertexArray(VAOs[0]);
	glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]);
	// 把之前定義的頂點數據復制到緩沖的內存中（靜態圖形方式）
	// glBufferData() // 復制數據到當前綁定緩沖（緩沖類型，數據大小，數據，顯存數據的管理方式）
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices0), vertices0, GL_STATIC_DRAW);
	// glVertexAttribPointer() // 解析頂點數據（1.頂點屬性[對應前面的 layout (location = 0)]，2.頂點屬性的大小[3分量向量]，
	//     3.數據類型[浮點數]，4.是否標准化為(-1,1)范圍內，5.單位步長，6.從起始位置的偏移量）
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
	glEnableVertexAttribArray(0);

	// 第2個三角形
	glBindVertexArray(VAOs[1]);
	glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices1), vertices1, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
	glEnableVertexAttribArray(0);

	// 解綁
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);

	// 創建游戲循環
	while (!glfwWindowShouldClose(window)) {
		// 事件處理
		glfwPollEvents();
		// 指定背景色（深藍色）
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);
		// 使用着色器程序， glDrawArrays()：繪制圖元函數
		glUseProgram(shaderProgram0);
		glBindVertexArray(VAOs[0]);
		//glDrawArrays(GL_TRIANGLES, 0, 3);
		glDrawArrays(GL_TRIANGLES, 0, 3);
		// 第2個三角形
		glUseProgram(shaderProgram1);
		glBindVertexArray(VAOs[1]);
		glDrawArrays(GL_TRIANGLES, 0, 3);
		glBindVertexArray(0);
		// 交換緩沖
		glfwSwapBuffers(window);
	}

	// 刪除 VAO 和 VBO，釋放空間
	glDeleteVertexArrays(1, VAOs);
	glDeleteBuffers(1, VBOs);
	// 釋放 GLFW 內存
	glfwTerminate();
	return 0;
}