model.cpp

#define STB_IMAGE_IMPLEMENTATION
#include "model.h"

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

void Model::loadModel(std::string path)
{
    Assimp::Importer import;
    // Request generation of smooth normals if the model doesn't provide them
    const aiScene *scene = import.ReadFile(path, aiProcess_Triangulate | aiProcess_FlipUVs | aiProcess_GenSmoothNormals);
    
    if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode){
        std::cout << "ERROR::ASSIMP::" << import.GetErrorString() << std::endl;
        return;
    }
    // Support both POSIX and Windows path separators when extracting directory
    size_t pos = path.find_last_of("/\\");
    if (pos != std::string::npos)
        directory = path.substr(0, pos);
    else
        directory = ".";

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

    for(unsigned int i = 0; i < mesh->mNumVertices; i++)
    {
        Vertex vertex;
        // process vertex positions, normals and texture coordinates
        glm::vec3 vector; 
        vector.x = mesh->mVertices[i].x;
        vector.y = mesh->mVertices[i].y;
        vector.z = mesh->mVertices[i].z; 
        vertex.Position = vector;

        // Normals may be missing for some meshes; guard against null pointer
        if (mesh->HasNormals() && mesh->mNormals)
        {
            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(0.0f, 0.0f, 0.0f);
        }

        // process material

        // Texture coordinates: check for the presence of channel 0
        if (mesh->HasTextureCoords(0) && 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);
    }
    // process indices
    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> Model::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;
}  

void Model::Draw(Shader &shader)
{
    for (unsigned int i = 0; i < meshes.size(); i++){
        meshes[i].Draw(shader);
    }
}


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

    unsigned int textureID;
    glGenTextures(1, &textureID);

    int width, height, nrComponents;
    stbi_set_flip_vertically_on_load(true);
    unsigned char *data = stbi_load(filename.c_str(), &width, &height, &nrComponents, 0);
    if (data)
    {
        GLenum format = GL_RGB; // Default to RGB
        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_NEAREST_MIPMAP_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

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

    return textureID;
}

void Model::DrawMesh(Shader &shader, unsigned int index)
{
    if (index < meshes.size())
    {
        meshes[index].Draw(shader);
    }
}