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GLM简单使用

glm是一个开源的对矩阵运算的库，下载地址：
https://github.com/g-truc/glm/releases
直接包含其头文件即可使用：

#include <glad/glad.h>//glad必须在glfw头文件之前包含
#include <GLFW/glfw3.h>
#include <iostream>
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"//GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#define GLM_ENABLE_EXPERIMENTAL
#include <glm/gtx/string_cast.hpp>void frameBufferSizeCallbakc(GLFWwindow* window, int width, int height)
{glViewport(0, 0, width, height);
}
void glfwKeyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
}GLuint program = 0;
GLuint vao = 0;
GLuint texture = 0;
glm::mat4 transform(1.0f);//4×4单位矩阵
//旋转
void doRotationTransform()
{//构建一个旋转矩阵，绕着z轴旋转45度角//rotate函数：用于生成旋转矩阵//bug1:rotate必须得到一个float类型的角度，c++的template//bug2:rotate函数接受的不是角度（degree），接收的弧度（radians）//注意点：radians函数也是模板函数，切记要传入float类型数据，加f后缀transform = glm::rotate(glm::mat4(1.0), glm::radians(90.f), glm::vec3(0.0, 0.0, 1.0));
}
//平移
void doTranslationTransform()
{transform = glm::translate(glm::mat4(1.0), glm::vec3(0.5f, 0.0, 0.0));
}
//缩放
void doScaleTransform()
{//x缩放0.1，y缩放0.5，z不缩放transform = glm::scale(glm::mat4(1.0), glm::vec3(0.1f, 0.5f, 1.0f));
}
//复合变换
void doTransform()
{glm::mat4 rotateMat = glm::rotate(glm::mat4(1.0f), glm::radians(90.0f), glm::vec3(0.0, 0.0, 1.0));glm::mat4 translateMat = glm::translate(glm::mat4(1.0f), glm::vec3(0.5f, 0.0f, 0.0f));//先旋转 再平移transform = translateMat * rotateMat;//先平移 后旋转//transform = rotateMat * translateMat;
}
float angle = 0.0f;
void doRotation()
{angle += 2.0f;//每一帧都会“重新”构建一个旋转矩阵transform = glm::rotate(glm::mat4(1.0f), glm::radians(angle), glm::vec3(0.0f, 0.0f, 1.0f));;
}
void prepareVAO()
{//positionsfloat positions[] = {-0.5f, -0.5f, 0.0f,0.5f, -0.5f, 0.0f,0.0f,  0.5f, 0.0f,};//颜色float colors[] = {1.0f, 0.0f,0.0f,0.0f, 1.0f,0.0f,0.0f, 0.0f,1.0f};//索引unsigned int indices[] = {0, 1, 2,};//uv坐标float uvs[] = {0.0f, 0.0f,1.0f, 0.0f,0.5f, 1.0f,};//2 VBO创建GLuint posVbo = 0;GLuint colorVbo = 0;GLuint uvVbo = 0;glGenBuffers(1, &posVbo);glBindBuffer(GL_ARRAY_BUFFER, posVbo);glBufferData(GL_ARRAY_BUFFER, sizeof(positions), positions, GL_STATIC_DRAW);glGenBuffers(1, &colorVbo);glBindBuffer(GL_ARRAY_BUFFER, colorVbo);glBufferData(GL_ARRAY_BUFFER, sizeof(colors), colors, GL_STATIC_DRAW);glGenBuffers(1, &uvVbo);glBindBuffer(GL_ARRAY_BUFFER, uvVbo);glBufferData(GL_ARRAY_BUFFER, sizeof(uvs), uvs, GL_STATIC_DRAW);//3 EBO创建GLuint ebo = 0;glGenBuffers(1, &ebo);glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);//4 VAO创建vao = 0;glGenVertexArrays(1, &vao);glBindVertexArray(vao);//5 绑定vbo ebo 加入属性描述信息//5.1 加入位置属性描述信息glBindBuffer(GL_ARRAY_BUFFER, posVbo);glEnableVertexAttribArray(0);glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);//5.2 加入颜色属性描述信息glBindBuffer(GL_ARRAY_BUFFER, colorVbo);glEnableVertexAttribArray(1);glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);//5.3 加入uv属性描述数据glBindBuffer(GL_ARRAY_BUFFER, uvVbo);glEnableVertexAttribArray(2);glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), (void*)0);//5.2 加入ebo到当前的vaoglBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);glBindVertexArray(0);
}
void prepareShader() {//1 完成vs与fs的源代码，并且装入字符串const char* vertexShaderSource ="#version 330 core\n""layout (location = 0) in vec3 aPos;\n""layout (location = 1) in vec3 aColor;\n""layout (location = 2) in vec2 aUV;\n""out vec3 color;\n""out vec2 uv;\n""uniform mat4 transform;\n""void main()\n""{\n""   vec4 position = vec4(aPos, 1.0);\n""   position = transform * position;\n""   gl_Position = position;\n""   color = aColor;\n""   uv = aUV;\n""}\0";const char* fragmentShaderSource ="#version 330 core\n""out vec4 FragColor;\n""in vec3 color;\n""in vec2 uv;\n""uniform sampler2D sampler;\n""void main()\n""{\n""   FragColor = texture(sampler, uv);\n""}\n\0";//2 创建Shader程序（vs、fs）GLuint vertex, fragment;vertex = glCreateShader(GL_VERTEX_SHADER);fragment = glCreateShader(GL_FRAGMENT_SHADER);//3 为shader程序输入shader代码glShaderSource(vertex, 1, &vertexShaderSource, NULL);glShaderSource(fragment, 1, &fragmentShaderSource, NULL);int success = 0;char infoLog[1024];//4 执行shader代码编译 glCompileShader(vertex);//检查vertex编译结果glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);if (!success) {glGetShaderInfoLog(vertex, 1024, NULL, infoLog);std::cout << "Error: SHADER COMPILE ERROR --VERTEX" << "\n" << infoLog << std::endl;}glCompileShader(fragment);//检查fragment编译结果glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);if (!success) {glGetShaderInfoLog(fragment, 1024, NULL, infoLog);std::cout << "Error: SHADER COMPILE ERROR --FRAGMENT" << "\n" << infoLog << std::endl;}//5 创建一个Program壳子program = glCreateProgram();//6 将vs与fs编译好的结果放到program这个壳子里glAttachShader(program, vertex);glAttachShader(program, fragment);//7 执行program的链接操作，形成最终可执行shader程序glLinkProgram(program);//检查链接错误glGetProgramiv(program, GL_LINK_STATUS, &success);if (!success) {glGetProgramInfoLog(program, 1024, NULL, infoLog);std::cout << "Error: SHADER LINK ERROR " << "\n" << infoLog << std::endl;}//清理glDeleteShader(vertex);glDeleteShader(fragment);
}void prepareTextrue()
{//1 stbImage 读取图片int width, height, channels;//--反转y轴stbi_set_flip_vertically_on_load(true);unsigned char* data = stbi_load("goku.jpg", &width, &height, &channels, STBI_rgb_alpha);//2 生成纹理并且激活单元绑定glGenTextures(1, &texture);//--激活纹理单元--glActiveTexture(GL_TEXTURE0);//--绑定纹理对象--glBindTexture(GL_TEXTURE_2D, texture);//3 传输纹理数据,开辟显存glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);//***释放数据stbi_image_free(data);//4 设置纹理的过滤方式glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);//5 设置纹理的包裹方式glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);//uglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);//v
}void render()
{//执行opengl画布清理操作glClear(GL_COLOR_BUFFER_BIT);//1.绑定当前的programglUseProgram(program);//2 更新Uniform的时候，一定要先UserProgram//2.1 通过名称拿到Uniform变量的位置LocationGLint location = glGetUniformLocation(program, "sampler");//2.2 通过Location更新Uniform变量的值glUniform1f(location, 0);GLint locationTransform = glGetUniformLocation(program, "transform");//transpose参数：表示是否对传输进去的矩阵数据进行转置glUniformMatrix4fv(locationTransform, 1, GL_FALSE, glm::value_ptr(transform));//3 绑定当前的vaoglBindVertexArray(vao);//4 发出绘制指令//glDrawArrays(GL_TRIANGLE_STRIP, 0, 6);glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, 0);
}int main()
{//初始化glfw环境glfwInit();//设置opengl主版本号glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);//设置opengl次版本号glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);//设置opengl启用核心模式glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);//创建窗体对象GLFWwindow* window = glfwCreateWindow(800, 600, "lenarnOpenGL", nullptr, nullptr);//设置当前窗体对象为opengl的绘制舞台glfwMakeContextCurrent(window);//窗体大小回调glfwSetFramebufferSizeCallback(window, frameBufferSizeCallbakc);//键盘相应回调glfwSetKeyCallback(window, glfwKeyCallback);//使用glad加载所有当前版本opengl的函数if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)){std::cout << "初始化glad失败" << std::endl;return -1;};//设置opengl视口大小和清理颜色glViewport(0, 0, 800, 600);glClearColor(0.2f, 0.3f, 0.3f, 1.0f);//shaderprepareShader();//vaoprepareVAO();//textureprepareTextrue();//doTransform();//执行窗体循环while (!glfwWindowShouldClose(window)){//接受并分发窗体消息//检查消息队列是否有需要处理的鼠标、键盘等消息//如果有的话就将消息批量处理，清空队列glfwPollEvents();doRotation();//渲染操作render();//切换双缓存glfwSwapBuffers(window);}//推出程序前做相关清理glfwTerminate();return 0;
}

上述代码分别实现了对图像进行旋转平移缩放的操作。
在VS中定义transform四维矩阵变量，将这个变量与位置向量进行相乘即可进行旋转平移缩放。

叠加变换

上面的旋转三角形可以通过叠加来实现

void doTransform()
{旋转三角形float angle = 1.0f;transform = glm::rotate(transform, glm::radians(angle), glm::vec3(0.0f, 0.0f, 1.0f));
}

在每一帧进行渲染时调用此函数即可