texture01.cpp

// 引入GLEW库 定义静态链接
#define GLEW_STATIC
#include <GLEW/glew.h>
// 引入GLFW库
#include <GLFW/glfw3.h>
// 引入SOIL库
#include <SOIL/SOIL.h>

#include <iostream>
#include <vector>

// 包含着色器加载库
#include "shader.h"

// 键盘回调函数原型声明
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods);

// 定义程序常量
const int WINDOW_WIDTH = 800, WINDOW_HEIGHT = 600;

int main(int argc, char** argv)
{
	
	if (!glfwInit())	// 初始化glfw库
	{
		std::cout << "Error::GLFW could not initialize GLFW!" << std::endl;
		return -1;
	}

	// 开启OpenGL 3.3 core profile
	std::cout << "Start OpenGL core profile version 3.3" << std::endl;
	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);

	// 创建窗口
	GLFWwindow* window = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT,
		"Demo of 2D texture", NULL, NULL);
	if (!window)
	{
		std::cout << "Error::GLFW could not create winddow!" << std::endl;
		glfwTerminate();
		return -1;
	}
	// 创建的窗口的context指定为当前context
	glfwMakeContextCurrent(window);

	// 注册窗口键盘事件回调函数
	glfwSetKeyCallback(window, key_callback);

	// 初始化GLEW 获取OpenGL函数
	glewExperimental = GL_TRUE; // 让glew获取所有拓展函数
	GLenum status = glewInit();
	if (status != GLEW_OK)
	{
		std::cout << "Error::GLEW glew version:" << glewGetString(GLEW_VERSION) 
			<< " error string:" << glewGetErrorString(status) << std::endl;
		glfwTerminate();
		return -1;
	}

	// 设置视口参数
	glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
	
	// Section1 准备顶点数据
	// 指定顶点属性数据 顶点位置 颜色 纹理
	GLfloat vertices[] = {
		-0.5f, -0.5f, 0.0f, 1.0f, 0.0f, 0.0f,0.0f, 0.0f,  // 0
		0.5f,  -0.5f, 0.0f, 0.0f, 1.0f, 0.0f,1.0f, 0.0f,  // 1
		0.5f,  0.5f,  0.0f, 0.0f, 0.0f, 1.0f,1.0f, 1.0f,  // 2
		-0.5f, 0.5f,  0.0f, 1.0f, 1.0f, 0.0f,0.0f, 1.0f   // 3
	};
	GLushort indices[] = {
		0, 1, 2,  // 第一个三角形
		0, 2, 3   // 第二个三角形
	};
	// 创建缓存对象
	GLuint VAOId, VBOId, EBOId;
	// Step1: 创建并绑定VAO对象
	glGenVertexArrays(1, &VAOId);
	glBindVertexArray(VAOId);
	// Step2: 创建并绑定VBO 对象 传送数据
	glGenBuffers(1, &VBOId);
	glBindBuffer(GL_ARRAY_BUFFER, VBOId);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
	// Step3: 创建并绑定EBO 对象 传送数据
	glGenBuffers(1, &EBOId);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBOId);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
	// Step4: 指定解析方式  并启用顶点属性
	// 顶点位置属性
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 
		8 * sizeof(GL_FLOAT), (GLvoid*)0);
	glEnableVertexAttribArray(0);
	// 顶点颜色属性
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE,
		8 * sizeof(GL_FLOAT), (GLvoid*)(3 * sizeof(GL_FLOAT)));
	glEnableVertexAttribArray(1);
	// 顶点纹理坐标
	glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE,
		8 * sizeof(GL_FLOAT), (GLvoid*)(6 * sizeof(GL_FLOAT)));
	glEnableVertexAttribArray(2);
	// glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0); // 注意不要解除EBO绑定
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);

	// Section2 准备着色器程序
	Shader shader("triangle.vertex", "triangle.frag");

	// Section3 准备纹理对象
	// Step1 创建并绑定纹理对象
	GLuint textureId;
	glGenTextures(1, &textureId);
	glBindTexture(GL_TEXTURE_2D, textureId);
	// Step2 设定wrap参数
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
	// Step3 设定filter参数
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
		GL_LINEAR_MIPMAP_LINEAR); // 为MipMap设定filter方法
	// Step4 加载纹理
	GLubyte *imageData = NULL;
	int picWidth, picHeight;
	imageData = SOIL_load_image("../../resources/textures/wood.png", 
		&picWidth, &picHeight, 0, SOIL_LOAD_RGB);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, picWidth, picHeight, 
		0, GL_RGB, GL_UNSIGNED_BYTE, imageData);
	glGenerateMipmap(GL_TEXTURE_2D);
	// Step5 释放纹理图片资源
	SOIL_free_image_data(imageData);
	glBindTexture(GL_TEXTURE_2D, 0);

	// 开始游戏主循环
	while (!glfwWindowShouldClose(window))
	{
		glfwPollEvents(); // 处理例如鼠标 键盘等事件

		// 清除颜色缓冲区 重置为指定颜色
		glClearColor(0.18f, 0.04f, 0.14f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// 这里填写场景绘制代码
		glBindVertexArray(VAOId);
		shader.use();
		// 启用纹理单元 绑定纹理对象
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, textureId);
		glUniform1i(glGetUniformLocation(shader.programId, "tex"), 0); // 设置纹理单元为0号
		// 使用索引绘制
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, 0);
		glBindVertexArray(0);
		glUseProgram(0);

		glfwSwapBuffers(window); // 交换缓存
	}
	// 释放资源
	glDeleteVertexArrays(1, &VAOId);
	glDeleteBuffers(1, &VBOId);
	glfwTerminate();
	return 0;
}
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
	if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, GL_TRUE); // 关闭窗口
	}
}