学习opengl之刚体绕自身轴运动

效果

这是一个可以绕自身轴运动的刚体

工具

glad、glfw(这个无所谓)、glm（这个也主要是为了和glad配合，使用eigen也行）

思路

已知

gl_Position = projection * view * model * vec4(aPos, 1.0f);

1.需要存储一个全局变量保存当前刚体的姿态。

glm::mat4 currentModel = glm::mat4(1.0f);

我们保存的是model。
2.使用变换矩阵右乘来表示沿着新的model的坐标系旋转，使用左乘来表示沿着原来的坐标系旋转。
因为我们要让刚体绕自身的轴旋转，所以采用右乘。
$$currentT=lastT\ast deltaT$$
$$lastT=current$$

3. 每次通过windows窗口消息机制来设置deltaT，opengl循环渲染时会使用这个增量。我使用的是三个角度增量来表示绕x,y,z轴的旋转。 这个经过learnopengl教程的入门部分就可以学会了。
   $$deltaT=RotateX(alpha)\ast RotateY(beta)\ast RotateZ(theta)$$
   代码如下：

while(1)
{
//currentModel = glm::rotate(currentModel, glm::degrees(deltaalpha), glm::vec3(0.0f, 1.f, 0.f));currentModel = glm::rotate(currentModel, glm::degrees(deltabeta), glm::vec3(1.0f, 0.f, 0.f));currentModel = glm::rotate(currentModel, glm::degrees(deltatheta), glm::vec3(0.0f, 0.f, 1.f));}

有了上面3点，就能保证看到的刚体是沿自己的轴运动了

较为完整的代码

总共6部分，stb_image.h、shader_m.h，main.cpp, 顶点着色器文件，片段着色器文件以及纹理图片，除了main.cpp，剩下都可以在learngl入门–(鼠标事件中)找到源代码，我在代码中修改了着色器文件 的名字和纹理的名字。

main.cpp，

#pragma execution_character_set("utf-8")
#include 
#include 
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"#include 
#include 
#include #include "shader_m.h"#include 
#include 
using namespace std;void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow* window);// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;// camera
glm::vec3 cameraPos = glm::vec3(0.f, 0.f, 3.0f);
glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f);
glm::vec3 cameraUp = glm::vec3(0.0f, 1.0f, 0.0f);float deltaalpha = 0.f;
float deltabeta = 0.f;
float deltatheta = 0.f; //左右转
glm::mat4 currentModel = glm::mat4(1.0f);// timing
float deltaTime = 0.0f;	// time between current frame and last frame
float lastFrame = 0.0f;int main()
{// glfw: initialize and configure// ------------------------------glfwInit();glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);#ifdef __APPLE__glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // uncomment this statement to fix compilation on OS X
#endif// glfw window creation// --------------------std::cout << "一个可以旋转的正方体（WASD，R）" << std::endl;GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "一个可以旋转的正方体（WASD，R）", NULL, NULL);if (window == NULL){std::cout << "Failed to create GLFW window" << std::endl;glfwTerminate();return -1;}glfwMakeContextCurrent(window);glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);// glad: load all OpenGL function pointers// ---------------------------------------if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)){std::cout << "Failed to initialize GLAD" << std::endl;return -1;}// configure global opengl state// -----------------------------glEnable(GL_DEPTH_TEST);// build and compile our shader zprogram// ------------------------------------Shader ourShader("pos.vs", "color.fs");// set up vertex data (and buffer(s)) and configure vertex attributes// ------------------------------------------------------------------float vertices[] = {-0.5f, -0.5f, -0.5f,  0.0f, 0.0f,0.5f, -0.5f, -0.5f,  1.0f, 0.0f,0.5f,  0.5f, -0.5f,  1.0f, 1.0f,0.5f,  0.5f, -0.5f,  1.0f, 1.0f,-0.5f,  0.5f, -0.5f,  0.0f, 1.0f,-0.5f, -0.5f, -0.5f,  0.0f, 0.0f,-0.5f, -0.5f,  0.5f,  0.0f, 0.0f,0.5f, -0.5f,  0.5f,  1.0f, 0.0f,0.5f,  0.5f,  0.5f,  1.0f, 1.0f,0.5f,  0.5f,  0.5f,  1.0f, 1.0f,-0.5f,  0.5f,  0.5f,  0.0f, 1.0f,-0.5f, -0.5f,  0.5f,  0.0f, 0.0f,-0.5f,  0.5f,  0.5f,  1.0f, 0.0f,-0.5f,  0.5f, -0.5f,  1.0f, 1.0f,-0.5f, -0.5f, -0.5f,  0.0f, 1.0f,-0.5f, -0.5f, -0.5f,  0.0f, 1.0f,-0.5f, -0.5f,  0.5f,  0.0f, 0.0f,-0.5f,  0.5f,  0.5f,  1.0f, 0.0f,0.5f,  0.5f,  0.5f,  1.0f, 0.0f,0.5f,  0.5f, -0.5f,  1.0f, 1.0f,0.5f, -0.5f, -0.5f,  0.0f, 1.0f,0.5f, -0.5f, -0.5f,  0.0f, 1.0f,0.5f, -0.5f,  0.5f,  0.0f, 0.0f,0.5f,  0.5f,  0.5f,  1.0f, 0.0f,-0.5f, -0.5f, -0.5f,  0.0f, 1.0f,0.5f, -0.5f, -0.5f,  1.0f, 1.0f,0.5f, -0.5f,  0.5f,  1.0f, 0.0f,0.5f, -0.5f,  0.5f,  1.0f, 0.0f,-0.5f, -0.5f,  0.5f,  0.0f, 0.0f,-0.5f, -0.5f, -0.5f,  0.0f, 1.0f,-0.5f,  0.5f, -0.5f,  0.0f, 1.0f,0.5f,  0.5f, -0.5f,  1.0f, 1.0f,0.5f,  0.5f,  0.5f,  1.0f, 0.0f,0.5f,  0.5f,  0.5f,  1.0f, 0.0f,-0.5f,  0.5f,  0.5f,  0.0f, 0.0f,-0.5f,  0.5f, -0.5f,  0.0f, 1.0f};// world space positions of our cubesglm::vec3 cubePositions[] = {glm::vec3(0.0f,  0.0f,  0.0f),//glm::vec3(2.0f,  5.0f, -15.0f),//glm::vec3(-1.5f, -2.2f, -2.5f),//glm::vec3(-3.8f, -2.0f, -12.3f),//glm::vec3(2.4f, -0.4f, -3.5f),//glm::vec3(-1.7f,  3.0f, -7.5f),//glm::vec3(1.3f, -2.0f, -2.5f),//glm::vec3(1.5f,  2.0f, -2.5f),//glm::vec3(1.5f,  0.2f, -1.5f),//glm::vec3(-1.3f,  1.0f, -1.5f)};unsigned int VBO, VAO;glGenVertexArrays(1, &VAO);glGenBuffers(1, &VBO);glBindVertexArray(VAO);glBindBuffer(GL_ARRAY_BUFFER, VBO);glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);// position attributeglVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);glEnableVertexAttribArray(0);// texture coord attributeglVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));glEnableVertexAttribArray(1);// load and create a texture // -------------------------unsigned int texture1, texture2;// texture 1// ---------glGenTextures(1, &texture1);glBindTexture(GL_TEXTURE_2D, texture1);// set the texture wrapping parametersglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);// set texture filtering parametersglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);// load image, create texture and generate mipmapsint width, height, nrChannels;stbi_set_flip_vertically_on_load(true); // tell stb_image.h to flip loaded texture's on the y-axis.unsigned char* data = stbi_load("wall.jpg", &width, &height, &nrChannels, 0);if (data){glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);glGenerateMipmap(GL_TEXTURE_2D);}else{std::cout << "Failed to load texture" << std::endl;}stbi_image_free(data);// texture 2// ---------glGenTextures(1, &texture2);glBindTexture(GL_TEXTURE_2D, texture2);// set the texture wrapping parametersglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);// set texture filtering parametersglTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);// load image, create texture and generate mipmapsdata = stbi_load("awesomeface.png", &width, &height, &nrChannels, 0);if (data){ // note that the awesomeface.png has transparency and thus an alpha channel, so make sure to tell OpenGL the data type is of GL_RGBAglTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);glGenerateMipmap(GL_TEXTURE_2D);}else{std::cout << "Failed to load texture" << std::endl;}stbi_image_free(data);// tell opengl for each sampler to which texture unit it belongs to (only has to be done once)// -------------------------------------------------------------------------------------------ourShader.use();ourShader.setInt("texture1", 0);ourShader.setInt("texture2", 1);// pass projection matrix to shader (as projection matrix rarely changes there's no need to do this per frame)// -----------------------------------------------------------------------------------------------------------glm::mat4 projection = glm::perspective(glm::radians(45.f), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f);ourShader.setMat4("projection", projection);// render loop// -----------while (!glfwWindowShouldClose(window)){// per-frame time logic// --------------------float currentFrame = glfwGetTime();deltaTime = currentFrame - lastFrame;lastFrame = currentFrame;// input// -----processInput(window);// render// ------glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// bind textures on corresponding texture unitsglActiveTexture(GL_TEXTURE0);glBindTexture(GL_TEXTURE_2D, texture1);glActiveTexture(GL_TEXTURE1);glBindTexture(GL_TEXTURE_2D, texture2);// activate shaderourShader.use();// camera/view transformationglm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp);ourShader.setMat4("view", view);// render boxesglBindVertexArray(VAO);for (unsigned int i = 0; i < 1; i++){// calculate the model matrix for each object and pass it to shader before drawingcurrentModel = glm::rotate(currentModel, glm::degrees(deltaalpha), glm::vec3(0.0f, 1.f, 0.f));currentModel = glm::rotate(currentModel, glm::degrees(deltabeta), glm::vec3(1.0f, 0.f, 0.f));currentModel = glm::rotate(currentModel, glm::degrees(deltatheta), glm::vec3(0.0f, 0.f, 1.f));ourShader.setMat4("model", currentModel);glDrawArrays(GL_TRIANGLES, 0, 36);}// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)// -------------------------------------------------------------------------------glfwSwapBuffers(window);glfwPollEvents();}// optional: de-allocate all resources once they've outlived their purpose:// ------------------------------------------------------------------------glDeleteVertexArrays(1, &VAO);glDeleteBuffers(1, &VBO);// glfw: terminate, clearing all previously allocated GLFW resources.// ------------------------------------------------------------------glfwTerminate();return 0;
}// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
void processInput(GLFWwindow* window)
{if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)glfwSetWindowShouldClose(window, true);deltaalpha = 0;deltabeta = 0;deltatheta = 0;float cameraSpeed = 2.5 * deltaTime;if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS){deltabeta -= 0.00001f;}if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS){deltabeta += 0.00001f;}if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS){deltaalpha -= 0.00001f;}if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS){deltaalpha += 0.00001f;}if (glfwGetKey(window, GLFW_KEY_J) == GLFW_PRESS){deltatheta -= 0.00001f;}if (glfwGetKey(window, GLFW_KEY_K) == GLFW_PRESS){deltatheta += 0.00001f;}if (glfwGetKey(window, GLFW_KEY_R) == GLFW_PRESS){currentModel = glm::mat4(1.0f);}
}// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{// make sure the viewport matches the new window dimensions; note that width and // height will be significantly larger than specified on retina displays.glViewport(0, 0, width, height);
}

着色器 pos.vs

#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec2 aTexCoord;out vec2 TexCoord;uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;void main()
{gl_Position = projection * view * model * vec4(aPos, 1.0f);TexCoord = vec2(aTexCoord.x, aTexCoord.y);
}

着色器 color.fs

#version 330 core
out vec4 FragColor;in vec2 TexCoord;// texture samplers
uniform sampler2D texture1;
uniform sampler2D texture2;void main()
{// linearly interpolate between both textures (80% container, 20% awesomeface)FragColor = mix(texture(texture1, TexCoord), texture(texture2, TexCoord), 0.2);
}

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