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[opengl/GLEW]GLEW 加载模型 [zt]

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浏览(98) - 2024-08-11 21:58:19 发表编辑

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[2024-08-11 21:59:11 最后更新]

[opengl/GLEW]GLEW 加载模型 [zt]

https://blog.csdn.net/mumufan05/article/details/100573960

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OpenGL学习笔记：加载模型

加载模型需要使用Assimp来屏蔽掉不同工具的模型文件，Assimp的gayhub
简单说一下，不同的3D编辑工具生成的模型文件格式是不同的，Assimp的作用就是将不同的模型文件转换成相同的格式，然后OpenGL再将Assimp的格式转换成OpenGL的数据格式。Assimp是怎么转换其他模型格式的我们不需要关心，但是我们需要关心转换后的统一的数据格式，因为我们需要将这个格式转换到OpenGL中。关于Assimp的统一数据格式这里就不多介绍了，大家可以自行查看原版教程或者是Assimp的官方资料
关于本例需要说明的是，原版教程中出于程序设计的角度对一些操作进行的面向对象的封装，但通常来说，封装的越好，对工作流程的理解也就越麻烦，这里为了方便理解Assimp的使用流程，尽量不去封装，只有一个必须写成函数的操作进行了函数封装。

#include <iostream>
#include <vector>
#include <windows.h>

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

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include <assimp/Importer.hpp>
#include <assimp/scene.h>
#include <assimp/postprocess.h>

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

// 定义摄像机的初始信息
glm::vec3 cameraPos = glm::vec3(0.0f, 0.0f, 3.0f);        // 位置向量
glm::vec3 cameraFront = glm::vec3(0.0f, 0.0f, -1.0f);    // 方向向量
glm::vec3 cameraUp = glm::vec3(0.0f, 1.0f, 0.0f);        // 上向量

                                                        // 控制移动速度
float deltaTime = 0.0f;
float lastFrame = 0.0f;

// 上一次鼠标的位置，默认是屏幕中心
float lastX = 400;
float lastY = 300;

float yaw = -90.0f;
float pitch = 0.0f;
float fov = 45.0f;

bool firstMouse = true;

// 本例需要两个着色器
const char *vertexShaderSource = R"1234(#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;

out vec2 TexCoords;

uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

void main()
{
    TexCoords = aTexCoords;
    gl_Position = projection * view * model * vec4(aPos, 1.0);
}
)1234";

// 这个是被光照射的物体的片段着色器，从uniform变量中接受物体的颜色和光源的颜色。
// 将光照的颜色和物体自身的颜色作分量相乘，结果就是最终要显示出来的颜色向量
const char *fragmentShaderSource = R"1234(#version 330 core
out vec4 FragColor;

in vec2 TexCoords;

uniform sampler2D texture_diffuse1;

void main()
{
    FragColor = texture(texture_diffuse1, TexCoords);
}
)1234";

struct Vertex {
    glm::vec3 Position;
    glm::vec3 Normal;
    glm::vec2 TexCoords;
};

struct Texture {
    unsigned int id;
    std::string type;
    aiString path; // 我们储存纹理的路径用于与其它纹理进行比较
};

struct Mesh
{
    std::vector<Vertex> vertices;
    std::vector<unsigned int> indices;
    std::vector<Texture> textures;

    unsigned int VAO, VBO, EBO;
};

std::vector<Mesh> meshs;
std::string strModelPath = "D:/OpenGL/nanosuit/nanosuit.obj";
std::string strModelDirectory = strModelPath.substr(0, strModelPath.find_last_of('/'));

void processNode(aiNode *node, const aiScene *scene)
{
    // 处理节点所有的网格（如果有的话）
    for (unsigned int i = 0; i < node->mNumMeshes; i++)
    {
        // 取出当前节点的网格
        // Scene下的mMeshes数组储存了真正的Mesh对象
        // 节点中的mMeshes数组保存的只是场景中网格数组的索引
        aiMesh *aimesh = scene->mMeshes[node->mMeshes[i]];

        // 取出网格后将网格的数据转换为OpenGL中的数据格式
        Mesh mesh;

        for (unsigned int j = 0; j < aimesh->mNumVertices; j++)
        {
            Vertex vertex;
            // 处理顶点位置、法线和纹理坐标
            glm::vec3 vector;
            vector.x = aimesh->mVertices[j].x;
            vector.y = aimesh->mVertices[j].y;
            vector.z = aimesh->mVertices[j].z;
            vertex.Position = vector;

            vector.x = aimesh->mNormals[j].x;
            vector.y = aimesh->mNormals[j].y;
            vector.z = aimesh->mNormals[j].z;
            vertex.Normal = vector;

            // 网格是否有纹理坐标？
            if (aimesh->mTextureCoords[0])
            {
                glm::vec2 vec;
                vec.x = aimesh->mTextureCoords[0][j].x;
                vec.y = aimesh->mTextureCoords[0][j].y;
                vertex.TexCoords = vec;
            }
            else
            {
                vertex.TexCoords = glm::vec2(0.0f, 0.0f);
            }

            mesh.vertices.push_back(vertex);
        }

        // 处理索引
        // 每个网格里都有一个face数组，每个元素都代表了一个图元，我们这里就是一个三角形
        // 而每个图元又包含多个顶点索引，就是之前索引缓冲对象章节中的那个索引
        // 有了顶点和索引就可以使用glDrawElements来绘图了，像之前章节中介绍的一样
        for (unsigned int j = 0; j < aimesh->mNumFaces; j++)
        {
            aiFace face = aimesh->mFaces[j];
            for (unsigned int k = 0; k < face.mNumIndices; k++)
                mesh.indices.push_back(face.mIndices[k]);
        }

        // 处理材质
        if (aimesh->mMaterialIndex >= 0)
        {
            // 取出材质
            aiMaterial *material = scene->mMaterials[aimesh->mMaterialIndex];
            // 加载漫反射
            for (unsigned int j = 0; j < material->GetTextureCount(aiTextureType_DIFFUSE); j++)
            {
                // 获取纹理文件路径
                aiString str;
                material->GetTexture(aiTextureType_DIFFUSE, j, &str);

                std::string filename = std::string(str.C_Str());
                filename = strModelDirectory + '/' + filename;

                // 读取纹理文件创建纹理
                unsigned int textureID;
                glGenTextures(1, &textureID);

                int width, height, nrComponents;
                unsigned char *data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0);
                if (data)
                {
                    GLenum format;
                    if (nrComponents == 1)
                        format = GL_RED;
                    else if (nrComponents == 3)
                        format = GL_RGB;
                    else if (nrComponents == 4)
                        format = GL_RGBA;

                    glBindTexture(GL_TEXTURE_2D, textureID);
                    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
                    glGenerateMipmap(GL_TEXTURE_2D);

                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

                    stbi_image_free(data);
                }
                else
                {
                    std::cout << "Texture failed to load at path: " << filename << std::endl;
                }

                Texture texture;
                texture.id = textureID;
                texture.type = "texture_diffuse";
                texture.path = str;
                mesh.textures.push_back(texture);
            }

            // 加载镜面反光
            for (unsigned int j = 0; j < material->GetTextureCount(aiTextureType_SPECULAR); j++)
            {
                // 获取纹理文件路径
                aiString str;
                material->GetTexture(aiTextureType_SPECULAR, j, &str);

                std::string filename = std::string(str.C_Str());
                filename = strModelDirectory + '/' + filename;

                // 读取纹理文件创建纹理
                unsigned int textureID;
                glGenTextures(1, &textureID);

                int width, height, nrComponents;
                unsigned char *data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0);
                if (data)
                {
                    GLenum format;
                    if (nrComponents == 1)
                        format = GL_RED;
                    else if (nrComponents == 3)
                        format = GL_RGB;
                    else if (nrComponents == 4)
                        format = GL_RGBA;

                    glBindTexture(GL_TEXTURE_2D, textureID);
                    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
                    glGenerateMipmap(GL_TEXTURE_2D);

                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
                    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

                    stbi_image_free(data);
                }
                else
                {
                    std::cout << "Texture failed to load at path: " << filename << std::endl;
                }

                Texture texture;
                texture.id = textureID;
                texture.type = "texture_specular";
                texture.path = str;
                mesh.textures.push_back(texture);
            }
        }

        // 顶点法线索引纹理之类的出读出来了，像之前章节一样，绑定VA0之类的
        glGenVertexArrays(1, &mesh.VAO);
        glGenBuffers(1, &mesh.VBO);
        glGenBuffers(1, &mesh.EBO);

        glBindVertexArray(mesh.VAO);
        glBindBuffer(GL_ARRAY_BUFFER, mesh.VBO);

        glBufferData(GL_ARRAY_BUFFER, mesh.vertices.size() * sizeof(Vertex), &mesh.vertices[0], GL_STATIC_DRAW);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mesh.EBO);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, mesh.indices.size() * sizeof(unsigned int),
            &mesh.indices[0], GL_STATIC_DRAW);

        // 顶点位置
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)0);
        // 顶点法线
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, Normal));
        // 顶点纹理坐标
        glEnableVertexAttribArray(2);
        glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)offsetof(Vertex, TexCoords));

        glBindVertexArray(0);

        meshs.push_back(mesh);
    }
    // 接下来对它的子节点重复这一过程
    for (unsigned int i = 0; i < node->mNumChildren; i++)
    {
        processNode(node->mChildren[i], scene);
    }
}

void framebuffer_size_callback(GLFWwindow *window, int width, int height)
{
    // 每次窗口变化时重新设置图形的绘制窗口，可以理解为画布
    glViewport(0, 0, width, height);
}

void processInput(GLFWwindow *window)
{
    if (glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS)
        glfwSetWindowShouldClose(window, true);

    // 由于前后平移方向上并没有改变，直接在观察方向上进行移动，所以直接加减就可以了
    // 但是左右平移需要在左右向量上进行加减，因此需要利用叉乘计算出右向量
    // glm::normalize是对右向量的标准化
    // 如果我们没对这个向量进行标准化，最后的叉乘结果会根据cameraFront变量返回大小不同的向量。
    // 如果我们不对向量进行标准化，我们就得根据摄像机的朝向不同加速或减速移动了，
    // 但如果进行了标准化移动就是匀速的。
    float cameraSpeed = 2.5f * deltaTime; // 相应调整
    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
        cameraPos += cameraSpeed * cameraFront;
    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
        cameraPos -= cameraSpeed * cameraFront;
    if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
        cameraPos -= glm::normalize(glm::cross(cameraFront, cameraUp)) * cameraSpeed;
    if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
        cameraPos += glm::normalize(glm::cross(cameraFront, cameraUp)) * cameraSpeed;
}

void cursor_position_callback(GLFWwindow* window, double x, double y)
{
    // 防止第一次进入时图像跳动
    if (firstMouse)
    {
        lastX = x;
        lastY = y;
        firstMouse = false;
    }

    float xoffset = x - lastX;
    float yoffset = lastY - y; // 注意这里是相反的，因为y坐标是从底部往顶部依次增大的
    lastX = x;
    lastY = y;

    // 判断右键是否按下，如果不判断右键按下，每次移动鼠标都会转动视角
    // 但计算偏移量必须在if外面，否则右键没有按下时鼠标移动不会更新last坐标导致下次右键图像跳动
    if (glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_RIGHT) == GLFW_PRESS)
    {
        float sensitivity = 0.5f;
        xoffset *= sensitivity;
        yoffset *= sensitivity;

        yaw += xoffset;
        pitch += yoffset;

        if (pitch > 89.0f)
            pitch = 89.0f;
        if (pitch < -89.0f)
            pitch = -89.0f;

        // 数学太渣，这里是真心看不懂
        glm::vec3 front;
        front.x = cos(glm::radians(pitch)) * cos(glm::radians(yaw));
        front.y = sin(glm::radians(pitch));
        front.z = cos(glm::radians(pitch)) * sin(glm::radians(yaw));
        cameraFront = glm::normalize(front);
    }
}

void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
    if (fov >= 1.0f && fov <= 45.0f)
        fov -= yoffset;
    if (fov <= 1.0f)
        fov = 1.0f;
    if (fov >= 45.0f)
        fov = 45.0f;
}

int main(int argc, char **argv)
{
    // 初始化，配置版本号，配置核心模式
    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

    // 创建窗口
    GLFWwindow *window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "mytest", NULL, NULL);
    if (!window)
    {
        std::cout << "Create Window Error!\n";
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);
    // 注册窗口大小变化的回调函数
    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    glfwSetCursorPosCallback(window, cursor_position_callback);
    glfwSetScrollCallback(window, scroll_callback);
    // 让鼠标消失
    //    glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);

    // 初始化glad
    // 我们给GLAD传入了用来加载系统相关的OpenGL函数指针地址的函数。
    // GLFW给我们的是glfwGetProcAddress，它根据我们编译的系统定义了正确的函数。
    if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
    {
        std::cout << "Failed to initialize GLAD" << std::endl;
        glfwTerminate();
        glfwDestroyWindow(window);
        return -1;
    }

    // 从模型文件中加载模型到OpenGL
    Assimp::Importer import;
    const aiScene *scene = import.ReadFile(strModelPath, aiProcess_Triangulate | aiProcess_FlipUVs);

    if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode)
    {
        std::cout << "ERROR::ASSIMP::" << import.GetErrorString() << std::endl;
        return -1;
    }

    // 递归处理所有子节点
    processNode(scene->mRootNode, scene);

    // 本例对着色器的使用并不复杂，下面简单实现一下
    int success;
    char infoLog[512] = { 0 };

    unsigned int vertexShader;
    vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        glGetShaderInfoLog(vertexShader, sizeof(infoLog), NULL, infoLog);
        std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    int fragmentShader;
    fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
    if (!success)
    {
        memset(infoLog, 0, sizeof(infoLog));
        glGetShaderInfoLog(fragmentShader, sizeof(infoLog), NULL, infoLog);
        std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
    }

    unsigned int shader;
    shader = glCreateProgram();

    glAttachShader(shader, vertexShader);
    glAttachShader(shader, fragmentShader);

    glLinkProgram(shader);

    glGetProgramiv(shader, GL_LINK_STATUS, &success);
    if (!success)
    {
        memset(infoLog, 0, sizeof(infoLog));
        glGetProgramInfoLog(shader, sizeof(infoLog), NULL, infoLog);
        std::cout << "ERROR::SHADER::PROGRAM::LINK_FAILED\n" << infoLog << std::endl;
    }

    glUseProgram(shader);
    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);


    // 启用深度测试
    glEnable(GL_DEPTH_TEST);

    // 创建渲染循环
    while (!glfwWindowShouldClose(window))
    {
        float currentFrame = glfwGetTime();
        deltaTime = currentFrame - lastFrame;
        lastFrame = currentFrame;

        // 处理输入事件
        processInput(window);

        // 清空背景颜色，这次设置为黑色背景
        glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
        // 由于我们使用了深度测试，所以需要再与上一个GL_DEPTH_BUFFER_BIT清楚深度缓冲
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        // 绘制物体
        glUseProgram(shader);


        glm::mat4 projection(1.0f);
        projection = glm::perspective(glm::radians(fov), 800.0f / 600.0f, 0.1f, 100.0f);

        glm::mat4 view(1.0f);
        view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp);
        glUniformMatrix4fv(glGetUniformLocation(shader, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
        glUniformMatrix4fv(glGetUniformLocation(shader, "view"), 1, GL_FALSE, glm::value_ptr(view));

        glm::mat4 model = glm::mat4(1.0f);
        glUniformMatrix4fv(glGetUniformLocation(shader, "model"), 1, GL_FALSE, glm::value_ptr(model));

        for (unsigned int i = 0; i < meshs.size(); i++)
        {
            Mesh mesh = meshs[i];
            unsigned int diffuseNr = 1;
            unsigned int specularNr = 1;
            for (unsigned int j = 0; j < meshs[i].textures.size(); j++)
            {
                glActiveTexture(GL_TEXTURE0 + j); // 在绑定之前激活相应的纹理单元
                                                  // 获取纹理序号（diffuse_textureN 中的 N）
                std::string number;
                std::string name = meshs[i].textures[j].type;
                if (name == "texture_diffuse")
                    number = std::to_string(diffuseNr++);
                else if (name == "texture_specular")
                    number = std::to_string(specularNr++);

                glUniform1f(glGetUniformLocation(shader, ("material." + name + number).c_str()), j);
                glBindTexture(GL_TEXTURE_2D, meshs[i].textures[j].id);
            }
            glActiveTexture(GL_TEXTURE0);

            // 绘制网格
            glBindVertexArray(meshs[i].VAO);
            glDrawElements(GL_TRIANGLES, meshs[i].indices.size(), GL_UNSIGNED_INT, 0);
            glBindVertexArray(0);
        }

        glfwPollEvents();
        glfwSwapBuffers(window);
        Sleep(1);
    }

    // 测试代码，先允许存在内存泄露
//     glDeleteVertexArrays(1, &cubeVAO);
//     glDeleteVertexArrays(1, &lightVAO);
//     glDeleteBuffers(1, &VBO);

    glfwTerminate();
    glfwDestroyWindow(window);

    return 0;
}

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