C++OpenGL实现三角形的绘制

2024-04-02 19:04:59 132人浏览独家记忆

摘要

目录一、绘制三角形1、初始化2、顶点输入3、数据处理4、顶点着色器和片段着色器5、渲染二、完整代码代码输出修改尺寸修改三角形颜色修改背景颜色线框模式一、绘制三角形 1、初始化（1）

一、绘制三角形

1、初始化

（1）初始化GLFW

//初始化GLFW
    glfwInit();//初始化GLFW
    glfwWindowHint(GLFW_CONTEXT_VERSioN_MAJOR, 3);//设置主版本号
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);//设置次版本号
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);//设置核心模式
    //glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);//Mac OS
    glfwWindowHint(GLFW_RESIZABLE, false);//关闭可调节窗口大小

（2）创建一个窗口

//创建窗口(宽、高、窗口名)
    auto window = glfwCreateWindow(screen_width, screen_hight, "Triangle", nullptr, nullptr);
    if (window == nullptr) {
        std::cout << "Failed to Create OpenGL Context" << std::endl;
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);

（3）初始化GLAD

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

（4）创建一个视口

//创建视口
    glViewport(0, 0, screen_width, screen_hight);

初始化代码（全）：

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

#include <iOStream>

const int screen_width = 800;
const int screen_hight = 600;

int main() {

	//初始化GLFW
	glfwInit();//初始化GLFW
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);//设置主版本号
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);//设置次版本号
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);//设置核心模式
	//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);//MAC OS
	glfwWindowHint(GLFW_RESIZABLE, false);//关闭可调节窗口大小
	
	//创建窗口(宽、高、窗口名)
	auto window = glfwCreateWindow(screen_width, screen_hight, "Triangle", nullptr, nullptr);
	if (window == nullptr) {
		std::cout << "Failed to Create OpenGL Context" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

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

	//创建视口
	glViewport(0, 0, screen_width, screen_hight);

	return 0;
}

2、顶点输入

坐标系规定

顶点坐标代码

//三角形的顶点数据
const float triangle[] = {
    //--位置--//
    -0.5f,-0.5f,0.0f,//左下
    0.5f,-0.5f,0.0f,//右下
    0.0f,0.5f,0.0f,//正上
};

3、数据处理

（1）VBO、VAO

//生成并绑定VBO
    GLuint vertex_buffer_object;
    glGenBuffers(1, &vertex_buffer_object);
    glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_object);
    //将顶点数据绑定至默认的缓冲中
    glBufferData(GL_ARRAY_BUFFER, sizeof(triangle), triangle, GL_STATIC_DRAW);

//生成并绑定VAO
    GLuint vertex_array_object;
    glGenVertexArrays(1, &vertex_array_object);
    glBindVertexArray(vertex_array_object);

（2）顶点属性

//设置顶点属性指针
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float),(void*)0);
    glEnableVertexAttribArray(0);

（3）解绑代码

//设置完成之后就可以解绑VBO、VAO了
    glBindVertexArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);

4、顶点着色器和片段着色器

//顶点着色器源码
    const char* vertex_shader_source =
        "#version 330 core\n"
        "layout (location = 0) in vec3 aPos;\n"
        "void main()\n"
        "{\n"
        "    gl_Position = vec4(aPos,1.0);\n"
        "}\n\0";

//片段着色器源码
    const char* fragment_shader_source =
        "#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";

//生成并编译着色器
    //顶点着色器
    int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
    glCompileShader(vertex_shader);
    int success;
    char info_log[512];
    // 检查着色器是否成功编译，如果编译失败，打印错误信息
    glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(vertex_shader, 512, NULL, info_log);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << info_log << std::endl;
    }
    // 片段着色器
    int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
    glCompileShader(fragment_shader);
    // 检查着色器是否成功编译，如果编译失败，打印错误信息
    glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(fragment_shader, 512, NULL, info_log);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << info_log << std::endl;
    }

// 链接顶点和片段着色器至一个着色器程序
    int shader_program = glCreateProgram();
    glAttachShader(shader_program, vertex_shader);
    glAttachShader(shader_program, fragment_shader);
    glLinkProgram(shader_program);
    // 检查着色器是否成功链接，如果链接失败，打印错误信息
    glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
    if (!success) {
        glGetProgramInfoLog(shader_program, 512, NULL, info_log);
        std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << info_log << std::endl;
    }
    // 删除着色器
    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);

// 线框模式
    //glPolyGonMode(GL_FRONT_AND_BACK, GL_LINE);

5、渲染

//渲染循环
	while (!glfwwindowshouldClose(window)) {

		// 清空颜色缓冲
		glClearColor(0.0f, 0.34f, 0.57f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// 使用着色器程序
		glUseProgram(shader_program);

		// 绘制三角形
		glBindVertexArray(vertex_array_object);                                    // 绑定VAO
		glDrawArrays(GL_TRIANGLES, 0, 3);                                          // 绘制三角形
		glBindVertexArray(0);                                                      // 解除绑定

		// 交换缓冲并且检查是否有触发事件(比如键盘输入、鼠标移动等）
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

    // 删除VAO和VBO
    glDeleteVertexArrays(1, &vertex_array_object);
    glDeleteBuffers(1, &vertex_buffer_object);

二、完整代码

代码

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

#include <iostream>

const int screen_width = 800;
const int screen_hight = 600;

//三角形的顶点数据
const float triangle[] = {
	//--位置--//
	-0.5f,-0.5f,0.0f,//左下
	0.5f,-0.5f,0.0f,//右下
	0.0f,0.5f,0.0f,//正上
};

int main() {

	//初始化GLFW
	glfwInit();//初始化GLFW
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);//设置主版本号
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);//设置次版本号
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);//设置核心模式
	//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);//MAC OS
	glfwWindowHint(GLFW_RESIZABLE, false);//关闭可调节窗口大小

	//创建窗口(宽、高、窗口名)
	auto window = glfwCreateWindow(screen_width, screen_hight, "Triangle", nullptr, nullptr);
	if (window == nullptr) {
		std::cout << "Failed to Create OpenGL Context" << std::endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

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

	//创建视口
	glViewport(0, 0, screen_width, screen_hight);

	//生成并绑定VBO
	GLuint vertex_buffer_object;
	glGenBuffers(1, &vertex_buffer_object);
	glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer_object);
	//将顶点数据绑定至默认的缓冲中
	glBufferData(GL_ARRAY_BUFFER, sizeof(triangle), triangle, GL_STATIC_DRAW);
	//生成并绑定VAO
	GLuint vertex_array_object;
	glGenVertexArrays(1, &vertex_array_object);
	glBindVertexArray(vertex_array_object);

	//设置顶点属性指针
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);//参数：顶点着色器位置值，分量，顶点数据类型，是否标准化，步长、数据偏移量
	glEnableVertexAttribArray(0);//开启0通道

	//设置完成之后就可以解绑VBO、VAO了
	glBindVertexArray(0);
	glBindBuffer(GL_ARRAY_BUFFER, 0);

	//顶点着色器源码
	const char* vertex_shader_source =
		"#version 330 core\n"
		"layout (location = 0) in vec3 aPos;\n"
		"void main()\n"
		"{\n"
		"	gl_Position = vec4(aPos,1.0);\n"
		"}\n\0";

	//片段着色器源码
	const char* fragment_shader_source =
		"#version 330 core\n"
		"out vec4 FragColor;\n"
		"void main()\n"
		"{\n"
		"	FragColor = vec4(1.0f,0.1f,0.1f,1.0f);\n"
		"}\n\0";

	//生成并编译着色器
	//顶点着色器
	int vertex_shader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
	glCompileShader(vertex_shader);
	int success;
	char info_log[512];
	// 检查着色器是否成功编译，如果编译失败，打印错误信息
	glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertex_shader, 512, NULL, info_log);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << info_log << std::endl;
	}
	// 片段着色器
	int fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
	glCompileShader(fragment_shader);
	// 检查着色器是否成功编译，如果编译失败，打印错误信息
	glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragment_shader, 512, NULL, info_log);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << info_log << std::endl;
	}
	// 链接顶点和片段着色器至一个着色器程序
	int shader_program = glCreateProgram();
	glAttachShader(shader_program, vertex_shader);
	glAttachShader(shader_program, fragment_shader);
	glLinkProgram(shader_program);
	// 检查着色器是否成功链接，如果链接失败，打印错误信息
	glGetProgramiv(shader_program, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shader_program, 512, NULL, info_log);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << info_log << std::endl;
	}
	// 删除着色器
	glDeleteShader(vertex_shader);
	glDeleteShader(fragment_shader);

	// 线框模式
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	//渲染循环
	while (!glfwWindowShouldClose(window)) {

		// 清空颜色缓冲
		glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// 使用着色器程序
		glUseProgram(shader_program);

		// 绘制三角形
		glBindVertexArray(vertex_array_object);                                    // 绑定VAO
		glDrawArrays(GL_TRIANGLES, 0, 3);                                          // 绘制三角形
		glBindVertexArray(0);                                                      // 解除绑定

		// 交换缓冲并且检查是否有触发事件(比如键盘输入、鼠标移动等）
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	// 删除VAO和VBO
	glDeleteVertexArrays(1, &vertex_array_object);
	glDeleteBuffers(1, &vertex_buffer_object);

	// 清理所有的资源并正确退出程序
	glfwTerminate();
	return 0;
}