C++OpenGL实现三角形的绘制

Olinda ·

更新时间:2024-09-21

· 606 次阅读

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）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;
}

输出