1.模型加载库

Assimp库能够导入很多种不同的模型文件格式（并也能够导出部分的格式），它会将所有的模型数据加载至Assimp的通用数据结构中。

当使用Assimp导入一个模型的时候，它通常会将整个模型加载进一个场景(Scene)对象，它会包含导入的模型/场景中的所有数据。Assimp会将场景载入为一系列的节点(Node)，每个节点包含了场景对象中所储存数据的索引，每个节点都可以有任意数量的子节点。Assimp数据结构的（简化）模型如下：

• 和材质和网格(Mesh)一样，所有的场景/模型数据都包含在Scene对象中。Scene对象也包含了场景根节点的引用。
• 场景的Root node（根节点）可能包含子节点（和其它的节点一样），它会有一系列指向场景对象中mMeshes数组中储存的网格数据的索引。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。
• 一个Mesh对象本身包含了渲染所需要的所有相关数据，像是顶点位置、法向量、纹理坐标、面(Face)和物体的材质。
• 一个网格包含了多个面。Face代表的是物体的渲染图元(Primitive)（三角形、方形、点）。一个面包含了组成图元的顶点的索引。由于顶点和索引是分开的，使用一个索引缓冲来渲染是非常简单的。
• 最后，一个网格也包含了一个Material对象，它包含了一些函数能让我们获取物体的材质属性，比如说颜色和纹理贴图（比如漫反射和镜面光贴图）。

2.编译Assimp库

下载库版本assimp-5.1.0

GitHub - assimp/assimp: The official Open-Asset-Importer-Library Repository. Loads 40+ 3D-file-formats into one unified and clean data structure.The official Open-Asset-Importer-Library Repository. Loads 40+ 3D-file-formats into one unified and clean data structure. - GitHub - assimp/assimp: The official Open-Asset-Importer-Library Repository. Loads 40+ 3D-file-formats into one unified and clean data structure.https://github.com/assimp/assimp准备好cmake，VisualStudio。

开始编译： 

注意编译出来的64/32位版本跟应用程序的版本对上。 

以下是编译好的库路径，需要bin、lib库，还有include下的文件。拷贝bin和lib下面的库文件，以及include/assimp/config.h文件到工程路径。

然后拷贝源码路径include/assimp到工程目录。

3.自定义网格类（Mesh）

网格(Mesh)代表的是单个的可绘制实体。一个网格应该至少需要一系列的顶点，每个顶点包含一个位置向量、一个法向量和一个纹理坐标向量。一个网格还应该包含用于索引绘制的索引以及纹理形式的材质数据（漫反射/镜面光贴图）。

#include <QOpenGLShaderProgram>
#include <QOpenGLFunctions_3_3_Core>
#include <string>
#include <vector>
using namespace std;
struct Vertex {
    QVector3D Position; //位置
    QVector3D Normal;   //法向量
    QVector2D TexCoords;    //纹理坐标
};
struct Texture {
    unsigned int id;    //纹理ID
    string type;    //类型
    string path;    //路径
};

class Mesh {
public:
    // mesh data
    vector<Vertex> vertices;
    vector<unsigned int> indices;
    vector<Texture> textures;

    void Draw(QOpenGLShaderProgram &shader);
    Mesh(QOpenGLFunctions_3_3_Core *glFuns,
         vector<Vertex> vertices, vector<unsigned int> indices, vector<Texture> textures);
private:
    // render data
    unsigned int VAO, VBO, EBO;
    void setupMesh();
private:
    QOpenGLFunctions_3_3_Core *m_glFuns;
};



#include "mesh.h"

Mesh::Mesh(QOpenGLFunctions_3_3_Core *glFuns,
           vector<Vertex> vertices, vector<unsigned int> indices, vector<Texture> textures)
    :m_glFuns(glFuns)
{
    this->vertices = vertices;
    this->indices = indices;
    this->textures = textures;
    setupMesh();
}

void Mesh::setupMesh()
{
    //创建VBO和VAO对象，并赋予ID
    m_glFuns->glGenVertexArrays(1, &VAO);
    m_glFuns->glGenBuffers(1, &VBO);
    m_glFuns->glGenBuffers(1,&EBO);
    //绑定VBO和VAO对象
    m_glFuns->glBindVertexArray(VAO);
    m_glFuns->glBindBuffer(GL_ARRAY_BUFFER, VBO);
    //为当前绑定到target的缓冲区对象创建一个新的数据存储。
    //如果data不是NULL，则使用来自此指针的数据初始化数据存储
    m_glFuns->glBufferData(GL_ARRAY_BUFFER, vertices.size()*sizeof(Vertex),
                           &vertices[0], GL_STATIC_DRAW);
    m_glFuns->glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    m_glFuns->glBufferData(GL_ELEMENT_ARRAY_BUFFER,
                           indices.size() * sizeof(unsigned int),&indices[0], GL_STATIC_DRAW);
    //告知显卡如何解析缓冲里的属性值
    m_glFuns->glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (void*)0);
    m_glFuns->glEnableVertexAttribArray(0);
    m_glFuns->glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex),
                                    (void*)offsetof(Vertex, Normal));

    m_glFuns->glEnableVertexAttribArray(1);
    m_glFuns->glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex),
                                    (void*)offsetof(Vertex, TexCoords));
    m_glFuns->glEnableVertexAttribArray(2);
}


void Mesh::Draw(QOpenGLShaderProgram &shader)
{
    unsigned int diffuseNr = 1;
    unsigned int specularNr = 1;
    for(unsigned int i = 0; i < textures.size(); i++) {
        m_glFuns->glActiveTexture(GL_TEXTURE0 + i);
        string number;
        string name = textures[i].type;
        if(name == "texture_diffuse")
            number = std::to_string(diffuseNr++);
        else if(name == "texture_specular")
            number = std::to_string(specularNr++);

        shader.setUniformValue(("material." + name + number).c_str(), i);
        m_glFuns->glBindTexture(GL_TEXTURE_2D, textures[i].id);

    }
    m_glFuns->glBindVertexArray(VAO);
    //m_glFuns->glDrawArrays(GL_TRIANGLES, 0, vertices.size());
    m_glFuns->glDrawElements(GL_TRIANGLES,indices.size(),GL_UNSIGNED_INT,0);
}

4.自定义模型类（Model）

一个模型包含多个网格，甚至是多个物体的模型。使用Assimp来加载模型，并将它转换至多个Mesh对象。

Model类包含了一个Mesh对象的vector，构造器需要我们给它一个文件路径。在构造器中它会直接通过loadModel来加载文件。

#ifndef MODEL_H
#define MODEL_H

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

#include "mesh.h"
#include <QOpenGLTexture>
class Model {
public:
    float m_maxX=-100.0;
    float m_maxY=-100.0;
    float m_minX=100.0;
    float m_minY=100.0;
    vector<Texture> textures_loaded;
    Model(QOpenGLFunctions_3_3_Core *glfuns,const char *path) :m_glFuns(glfuns) {

        loadModel(path);
    }
    void Draw(QOpenGLShaderProgram &shader) {
        for(unsigned int i = 0; i < meshes.size(); i++)
            meshes[i].Draw(shader);

    }

private:
    // model data
    QOpenGLFunctions_3_3_Core *m_glFuns;
    vector<Mesh> meshes;
    string directory;
    void loadModel(string path);

    void processNode(aiNode *node, const aiScene *scene);
    Mesh processMesh(aiMesh *mesh, const aiScene *scene);
    vector<Texture> loadMaterialTextures(aiMaterial *mat, aiTextureType type, string typeName);
    unsigned int TextureFromFile(const char *path, const string &directory);
};

#endif // MODEL_H



#include "model.h"

void Model::loadModel(string path)
{
    Assimp::Importer import;
    const aiScene *scene = import.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);
    if(!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) {
        qDebug() << "ERROR::ASSIMP::" << import.GetErrorString();
        return;
    }
    directory = path.substr(0, path.find_last_of('/'));
    processNode(scene->mRootNode, scene);
}

void Model::processNode(aiNode *node, const aiScene *scene)
{
    // process all the node's meshes (if any)
    for(unsigned int i = 0; i < node->mNumMeshes; i++) {
        aiMesh *mesh = scene->mMeshes[node->mMeshes[i]];
        meshes.push_back(processMesh(mesh, scene));
    }
    // then do the same for each of its children
    for(unsigned int i = 0; i < node->mNumChildren; i++) {
        processNode(node->mChildren[i], scene);
    }
}

Mesh Model::processMesh(aiMesh *mesh, const aiScene *scene)
{
    vector<Vertex> vertices;
    vector<unsigned int> indices;
    vector<Texture> textures;
    for(unsigned int i = 0; i < mesh->mNumVertices; i++) {
        if(m_maxX<mesh->mVertices[i].x) m_maxX=mesh->mVertices[i].x;
        if(m_maxY<mesh->mVertices[i].y) m_maxY=mesh->mVertices[i].y;
        if(m_minX>mesh->mVertices[i].x) m_minX=mesh->mVertices[i].x;
        if(m_minY>mesh->mVertices[i].y) m_minY=mesh->mVertices[i].y;
        Vertex vertex;
        // 处理顶点位置、法线和纹理坐标
        QVector3D vector;
        vector.setX(mesh->mVertices[i].x);
        vector.setY(mesh->mVertices[i].y);
        vector.setZ(mesh->mVertices[i].z);
        vertex.Position = vector;

        vector.setX(mesh->mNormals[i].x);
        vector.setY(mesh->mNormals[i].y);
        vector.setZ(mesh->mNormals[i].z);
        vertex.Normal = vector;

        if(mesh->mTextureCoords[0]) // 有纹理坐标？
        {
            QVector2D vec;
            vec.setX(mesh->mTextureCoords[0][i].x);
            vec.setY(mesh->mTextureCoords[0][i].y);
            vertex.TexCoords = vec;
        } else
            vertex.TexCoords = QVector2D(0.0f, 0.0f);

        vertices.push_back(vertex);
    }
    // 处理索引
    for(unsigned int i = 0; i < mesh->mNumFaces; i++) {
        aiFace face = mesh->mFaces[i];
        for(unsigned int j = 0; j < face.mNumIndices; j++)
            indices.push_back(face.mIndices[j]);
    }

    // 处理材质
    if(mesh->mMaterialIndex >= 0) {
        aiMaterial *material = scene->mMaterials[mesh->mMaterialIndex];
        vector<Texture> diffuseMaps =
                loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
        textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
        vector<Texture> specularMaps =
                loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
        textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
    }
    return Mesh(m_glFuns,vertices, indices, textures);

}

vector<Texture> Model::loadMaterialTextures(aiMaterial *mat, aiTextureType type, string typeName)
{
    vector<Texture> textures;
    for(unsigned int i = 0; i < mat->GetTextureCount(type); i++) {
        aiString str;
        mat->GetTexture(type, i, &str);
        bool skip = false;
        for(unsigned int j = 0; j < textures_loaded.size(); j++) {
            if(std::strcmp(textures_loaded[j].path.data(), str.C_Str()) == 0) {
                textures.push_back(textures_loaded[j]);
                skip = true;
                break;
            }
        }
        if(!skip){
            Texture texture;
            texture.id = TextureFromFile(str.C_Str(), directory);
            texture.type = typeName;
            texture.path = str.C_Str();
            textures.push_back(texture);
            textures_loaded.push_back(texture);
        }
    }
    return textures;
}

unsigned int Model::TextureFromFile(const char *path, const string &directory)
{
    string filename = string(path);
    filename = directory + '/' + filename;

    QOpenGLTexture * texture=new QOpenGLTexture(QImage(filename.c_str()).mirrored());
    if(texture==NULL) qDebug()<<"texture is NULL";
    else qDebug()<<filename.c_str()<<"loaded";

    return texture->textureId();
}

5.加载模型

#include "axbopemglwidget.h"

const unsigned int timeOutmSec=50;
unsigned int VAO,VBO,lightVAO;
QVector3D lightPos(1.2f, 1.0f, 2.0f);
QVector3D lightColor(1.0f, 1.0f, 1.0f);
QVector3D objectColor(1.0f, 0.5f, 0.31f);
QVector3D viewInitPos(0.0,0.0,5.0);
AXBOpemglWidget::AXBOpemglWidget(QWidget *parent) : QOpenGLWidget(parent)
{
    connect(&m_timer,SIGNAL(timeout()),this,SLOT(on_timeout()));
    m_timer.start(timeOutmSec);
    m_time.start();
    m_camera.Position=viewInitPos;
    setFocusPolicy(Qt::StrongFocus);
    //setMouseTracking(true);
}

AXBOpemglWidget::~AXBOpemglWidget()
{
    makeCurrent();
    glDeleteBuffers(1,&VBO);
    glDeleteVertexArrays(1,&VAO);
    glDeleteVertexArrays(1,&lightVAO);
    doneCurrent();
}

void AXBOpemglWidget::loadModel(string path)
{
    if(m_model !=NULL)
        delete m_model;

    m_model=NULL;
    makeCurrent();
    m_model=new Model(QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_3_3_Core>()
                ,path.c_str());
    m_camera.Position=cameraPosInit(m_model->m_maxY,m_model->m_minY);
    doneCurrent();
}

void AXBOpemglWidget::initializeGL()
{
    initializeOpenGLFunctions();
    //创建VBO和VAO对象，并赋予ID
    bool success;
    m_ShaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex,":/shaders/shaders/shapes.vert");
    m_ShaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment,":/shaders/shaders/shapes.frag");
    success=m_ShaderProgram.link();
    if(!success) qDebug()<<"ERR:"<<m_ShaderProgram.log();   
}

void AXBOpemglWidget::resizeGL(int w, int h)
{
    Q_UNUSED(w);
    Q_UNUSED(h);
}

void AXBOpemglWidget::paintGL()
{
    if(m_model==NULL) return;
    QMatrix4x4 model;
    QMatrix4x4 view;
    QMatrix4x4 projection;
   // float time=m_time.elapsed()/50.0;
    projection.perspective(m_camera.Zoom,(float)width()/height(),0.1,100);
    view=m_camera.GetViewMatrix();
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glEnable(GL_DEPTH_TEST);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    m_ShaderProgram.bind();
    m_ShaderProgram.setUniformValue("projection", projection);
    m_ShaderProgram.setUniformValue("view", view);
    //model.rotate(time, 1.0f, 1.0f, 0.5f);

    m_ShaderProgram.setUniformValue("viewPos",m_camera.Position);

    // light properties, note that all light colors are set at full intensity
    m_ShaderProgram.setUniformValue("light.ambient", 0.4f, 0.4f, 0.4f);
    m_ShaderProgram.setUniformValue("light.diffuse", 0.9f, 0.9f, 0.9f);
    m_ShaderProgram.setUniformValue("light.specular", 1.0f, 1.0f, 1.0f);
    // material properties
    m_ShaderProgram.setUniformValue("material.shininess", 32.0f);
    m_ShaderProgram.setUniformValue("light.direction", -0.2f, -1.0f, -0.3f);
    m_ShaderProgram.setUniformValue("model", model);
    m_model->Draw(m_ShaderProgram);
}

void AXBOpemglWidget::wheelEvent(QWheelEvent *event)
{
    m_camera.ProcessMouseScroll(event->angleDelta().y()/120);
}

void AXBOpemglWidget::keyPressEvent(QKeyEvent *event)
{
    float deltaTime=timeOutmSec/1000.0;

    switch (event->key()) {
    case Qt::Key_W: m_camera.ProcessKeyboard(FORWARD,deltaTime);break;
    case Qt::Key_S: m_camera.ProcessKeyboard(BACKWARD,deltaTime);break;
    case Qt::Key_D: m_camera.ProcessKeyboard(RIGHT,deltaTime);break;
    case Qt::Key_A: m_camera.ProcessKeyboard(LEFT,deltaTime);break;
    case Qt::Key_Q: m_camera.ProcessKeyboard(DOWN,deltaTime);break;
    case Qt::Key_E: m_camera.ProcessKeyboard(UP,deltaTime);break;
    case Qt::Key_Space: m_camera.Position=viewInitPos;break;

    default:break;
    }
}

void AXBOpemglWidget::mouseMoveEvent(QMouseEvent *event)
{
    if(event->buttons() & Qt::RightButton){
        static QPoint lastPos(width()/2,height()/2);
        auto currentPos=event->pos();
        QPoint deltaPos=currentPos-lastPos;
        lastPos=currentPos;

        m_camera.ProcessMouseMovement(deltaPos.x(),-deltaPos.y());
    }
}

void AXBOpemglWidget::on_timeout()
{
    update();
}

QVector3D AXBOpemglWidget::cameraPosInit(float maxY, float minY)
{
    QVector3D temp={0,0,0};
    float height=maxY-minY;
    temp.setZ(1.5*height);
    if(minY>=0)
        temp.setY(height/2.0);
    viewInitPos=temp;
    return temp;
}

完整工程：

https://download.csdn.net/download/wzz953200463/87919672https://download.csdn.net/download/wzz953200463/87919672