C++ Assimp Model Loading Code

#pragma once

#include <GLFW\glfw3.h>
#include <glad\glad.h>
#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <map>
#include <vector>
#include <glm\glm.hpp>
#include "lodepng.h"
#include <assimp\Importer.hpp>
#include <assimp\scene.h>
#include <assimp\postprocess.h>
#include "Models.h"

struct Vertex
{
    glm::vec3 position;
    glm::vec3 normal;
    glm::vec2 uv;
};

static Mesh process_mesh(aiMesh *mesh, const aiScene *scene)
{
    std::vector<Vertex> vertices;
    std::vector<GLuint> indices;

    for (GLuint i = 0; i < mesh->mNumVertices; i++)
    {
        Vertex vertex;
        glm::vec3 vector;

        vector.x = mesh->mVertices[i].x;
        vector.y = mesh->mVertices[i].y;
        vector.z = mesh->mVertices[i].z;
        vertex.position = vector;

        if (mesh->mNormals != nullptr)
        {
            vector.x = mesh->mNormals[i].x;
            vector.y = mesh->mNormals[i].y;
            vector.z = mesh->mNormals[i].z;
            vertex.normal = vector;
        }
        else
        {
            vertex.normal = glm::vec3(0, 0, 0);
        }

        if (mesh->mTextureCoords[0])
        {
            glm::vec2 uv;
            uv.x = mesh->mTextureCoords[0][i].x;
            uv.y = mesh->mTextureCoords[0][i].y;
            vertex.uv = uv;
        }
        else
        {
            vertex.uv = glm::vec2(0, 0);
        }

        vertices.push_back(vertex);
    }

    for (GLuint i = 0; i < mesh->mNumFaces; i++)
    {
        aiFace face = mesh->mFaces[i];

        for (GLuint j = 0; j < face.mNumIndices; j++)
        {
            indices.push_back(face.mIndices[j]);
        }
    }

    std::vector<GLfloat> vertices_float;
    for (GLuint i = 0; i < vertices.size(); i++)
    {
        Vertex v = vertices[i];

        vertices_float.push_back(v.position.x);
        vertices_float.push_back(v.position.y);
        vertices_float.push_back(v.position.z);

        vertices_float.push_back(v.normal.x);
        vertices_float.push_back(v.normal.y);
        vertices_float.push_back(v.normal.z);

        vertices_float.push_back(v.uv.x);
        vertices_float.push_back(v.uv.y);
    }

    return Mesh(vertices_float, indices);

}

static void process_node(aiNode *node, const aiScene *scene, std::vector<Mesh> *meshes)
{

    for (GLuint i = 0; i < node->mNumMeshes; i++)
    {
        aiMesh *mesh = scene->mMeshes[node->mMeshes[i]];

        meshes->push_back(process_mesh(mesh, scene));
    }

    for (GLuint i = 0; i < node->mNumChildren; i++)
    {
        process_node(node->mChildren[i], scene, meshes);
    }

}

static Model load_model(const char *path)
{
    Assimp::Importer importer;
    const aiScene *assimp_scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs);

    if (!assimp_scene || assimp_scene->mFlags == AI_SCENE_FLAGS_INCOMPLETE || !assimp_scene->mRootNode)
    {
        std::cout << "LOADER::LOAD_MODEL::ASSIMP::ERROR\n" << importer.GetErrorString() << "\n";
        return Model(std::vector<Mesh>());
    }

    std::vector<Mesh> meshes = std::vector<Mesh>();
    process_node(assimp_scene->mRootNode, assimp_scene, &meshes);

    importer.~Importer();
    return Model(meshes);
}

static GLuint load_texture(const char *path)
{
    GLuint texture;
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    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);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    std::vector<unsigned char> buf;
    unsigned int error, width, height;
    if ((error = lodepng::decode(buf, width, height, path, LodePNGColorType::LCT_RGBA)) != 0)
    {
        std::cout << "LOADER::LOAD_TEXTURE::ERROR::TEXTURE_LOAD_FAILED";
    }

    unsigned char* image = buf.data();
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, image);
    glGenerateMipmap(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 0);

    return texture;
}