model.h

#ifndef OPENGLPROJ_MODEL_H
#define OPENGLPROJ_MODEL_H

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

unsigned int TextureFromFile(const char *path, const std::string &directory);

class Model {
public:
    Model(const char *path) {
        loadModel(path);
    }
    void Draw(Shader &shader) {
        for(int i = 0; i < meshes.size(); i++) {
            meshes[i].Draw(shader);
        }
    }
private:
    std::vector<Mesh> meshes;
    std::string directory;
    std::vector<Texture> textures_loaded;

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

        processNode(scene->mRootNode, scene);
    }


    void processNode(aiNode *node, const aiScene *scene) {

        for(unsigned int i = 0; i < node->mNumMeshes; i++) {
            aiMesh *mesh = scene->mMeshes[node->mMeshes[i]];
            meshes.push_back(processMesh(mesh, scene));
        }

        for(unsigned int i = 0; i < node->mNumChildren; i++) {
            processNode(node->mChildren[i], scene);
        }
    }


    Mesh processMesh(aiMesh *mesh, const aiScene *scene) {
        std::vector<Vertex> vertices;
        std::vector<unsigned int> indices;
        std::vector<Texture> textures;

        for(unsigned int i = 0; i < mesh->mNumVertices; i++) {
            Vertex vertex;
            vertex.Position.x = mesh->mVertices[i].x;
            vertex.Position.y = mesh->mVertices[i].y;
            vertex.Position.z = mesh->mVertices[i].z;

            vertex.Normal.x = mesh->mNormals[i].x;
            vertex.Normal.y = mesh->mNormals[i].y;
            vertex.Normal.z = mesh->mNormals[i].z;

            if(mesh->mTextureCoords[0]) {
                glm::vec2 vec;
                vec.x = mesh->mTextureCoords[0][i].x;
                vec.y = mesh->mTextureCoords[0][i].y;
                vertex.TexCoords = vec;
            } else {
                vertex.TexCoords = glm::vec2(0.0f, 0.0f);
            }
            vertices.push_back(vertex);
        }

        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]);
        }

        if(mesh->mMaterialIndex >= 0) {
            aiMaterial *material = scene->mMaterials[mesh->mMaterialIndex];
            std::vector<Texture> diffuseMaps = loadMaterialTextures(material,
                                                aiTextureType_DIFFUSE, "texture_diffuse");
            textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
            std::vector<Texture> specularMaps = loadMaterialTextures(material,
                                                aiTextureType_SPECULAR, "texture_specular");
            textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
        }

        return Mesh(vertices, indices, textures);
    }

    std::vector<Texture> loadMaterialTextures(aiMaterial *mat, aiTextureType type, std::string typeName){
        std::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) {   // if texture hasn't been loaded already, load it
                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); // add to loaded textures
            }
        }

        return textures;
    }
};

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

    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: " << path << std::endl;
        stbi_image_free(data);
    }

    return textureID;
}

#endif //OPENGLPROJ_MODEL_H