Model.cpp

#include "Model.h"


void Model::loadModel(string const& path)
{
    //std::cout << "in importer\n";
    // read file via ASSIMP
    Assimp::Importer importer;
    const aiScene* scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_GenSmoothNormals | aiProcess_FlipUVs | aiProcess_CalcTangentSpace);
    // check for errors
    //std::cout << "after importer\n";

    if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) // if is Not Zero
    {
        std::cout << "ERROR::ASSIMP:: " << importer.GetErrorString() << endl;
        return;   

    }
    // retrieve the directory path of the filepath
    directory = path.substr(0, path.find_last_of('/'));
    
    //std::cout << path << "\n";

    // process ASSIMP's root node recursively
    processNode(scene->mRootNode, scene);
}


// processes a node in a recursive fashion. Processes each individual mesh located at the node and repeats this process on its children nodes (if any).
void Model::processNode(aiNode* node, const aiScene* scene)
{
    //std::printf(" found %d meshes\n", node->mNumMeshes);

    // process each mesh located at the current node
    for (unsigned int i = 0; i < node->mNumMeshes; i++)
    {
        // the node object only contains indices to index the actual objects in the scene. 
        // the scene contains all the data, node is just to keep stuff organized (like relations between nodes).
        aiMesh* mesh = scene->mMeshes[node->mMeshes[i]];
        meshes.push_back(processMesh(mesh, scene));
    }
    // after we've processed all of the meshes (if any) we then recursively process each of the children nodes
    for (unsigned int i = 0; i < node->mNumChildren; i++)
    {
        processNode(node->mChildren[i], scene);
    }

}


Mesh Model::processMesh(aiMesh* mesh, const aiScene* scene)
{
    // data to fill
    vector<Vertex> vertices;
    vector<unsigned int> indices;
    vector<Texture2D> textures;

    // walk through each of the mesh's vertices
    for (unsigned int i = 0; i < mesh->mNumVertices; i++)
    {
        Vertex vertex;
        glm::vec3 vector; // we declare a placeholder vector since assimp uses its own vector class that doesn't directly convert to glm's vec3 class so we transfer the data to this placeholder glm::vec3 first.
        SetVertexBoneDataToDefault(vertex);

        // positions
        vector.x = mesh->mVertices[i].x;
        vector.y = mesh->mVertices[i].y;
        vector.z = mesh->mVertices[i].z;
        vertex.Position = vector;

        boundingBox = { glm::max(vector.x , boundingBox[0]) , glm::min(vector.x, boundingBox[1]) , glm::max(vector.y, boundingBox[2]) , glm::min(vector.y, boundingBox[3]) , glm::max(vector.z, boundingBox[4]), glm::min(vector.z, boundingBox[5])};

        // normals
        if (mesh->HasNormals())
        {
            vector.x = mesh->mNormals[i].x;
            vector.y = mesh->mNormals[i].y;
            vector.z = mesh->mNormals[i].z;
            vertex.Normal = vector;
        }
        // texture coordinates
        if (mesh->mTextureCoords[0]) // does the mesh contain texture coordinates?
        {
            glm::vec2 vec;
            // a vertex can contain up to 8 different texture coordinates. We thus make the assumption that we won't 
            // use models where a vertex can have multiple texture coordinates so we always take the first set (0).
            vec.x = mesh->mTextureCoords[0][i].x * tilingFactor;
            vec.y = mesh->mTextureCoords[0][i].y * tilingFactor;
            vertex.TexCoords = vec;
            // tangent
            vector.x = mesh->mTangents[i].x;
            vector.y = mesh->mTangents[i].y;
            vector.z = mesh->mTangents[i].z;
            vertex.Tangent = vector;
            // bitangent
            vector.x = mesh->mBitangents[i].x;
            vector.y = mesh->mBitangents[i].y;
            vector.z = mesh->mBitangents[i].z;
            vertex.Bitangent = vector;
        }
        else
            vertex.TexCoords = glm::vec2(0.0f, 0.0f);

        vertices.push_back(vertex);
    }
    // now wak through each of the mesh's faces (a face is a mesh its triangle) and retrieve the corresponding vertex indices.
    for (unsigned int i = 0; i < mesh->mNumFaces; i++)
    {
        aiFace face = mesh->mFaces[i];
        // retrieve all indices of the face and store them in the indices vector
        for (unsigned int j = 0; j < face.mNumIndices; j++)
            indices.push_back(face.mIndices[j]);
    }
    // process materials
    aiMaterial* material = scene->mMaterials[mesh->mMaterialIndex];
    // we assume a convention for sampler names in the shaders. Each diffuse texture should be named
    // as 'texture_diffuseN' where N is a sequential number ranging from 1 to MAX_SAMPLER_NUMBER. 
    // Same applies to other texture as the following list summarizes:
    // diffuse: texture_diffuseN
    // specular: texture_specularN
    // normal: texture_normalN

    // 1. diffuse maps
    vector<Texture2D> diffuseMaps = loadMaterialTextures(material, aiTextureType_DIFFUSE, TextureType::DIFFUSE , scene);
    textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
    // 2. specular maps
    vector<Texture2D> specularMaps = loadMaterialTextures(material, aiTextureType_SPECULAR, TextureType::SPECULAR , scene);
    textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
    // 3. normal maps
    std::vector<Texture2D> normalMaps = loadMaterialTextures(material, aiTextureType_HEIGHT, TextureType::NORMAL , scene);
    textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
    // 4. height maps
    std::vector<Texture2D> heightMaps = loadMaterialTextures(material, aiTextureType_AMBIENT, TextureType::HEIGHT , scene);
    textures.insert(textures.end(), heightMaps.begin(), heightMaps.end());

    ExtractBoneWeightForVertices(vertices, mesh, scene);

    // return a mesh object created from the extracted mesh data
    return Mesh(vertices, indices, textures);
}

// checks all material textures of a given type and loads the textures if they're not loaded yet.
// the required info is returned as a Texture struct.
vector<Texture2D> Model::loadMaterialTextures(aiMaterial* mat, aiTextureType type, TextureType typeName ,const aiScene* scene)
{
    vector<Texture2D> textures;
    for (unsigned int i = 0; i < mat->GetTextureCount(type); i++)
    {
        aiString str;
        mat->GetTexture(type, i, &str);
        // check if texture was loaded before and if so, continue to next iteration: skip loading a new texture
        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; // a texture with the same filepath has already been loaded, continue to next one. (optimization)
                break;
            }
        }
        if (!skip)
        {   
            
            // if texture hasn't been loaded already, load it
            if (auto textureEmbedded = scene->GetEmbeddedTexture(str.C_Str())) {
                //std::cout << "embedded textures\n";
                Texture2D texture(textureEmbedded, false);
                texture.type = typeName;
                textures.push_back(texture);
                textures_loaded.push_back(texture);
                //returned pointer is not null, read texture from memory
            }
            else {
                Texture2D texture(str.C_Str(), this->directory, false);
                texture.type = typeName;
                textures.push_back(texture);
                textures_loaded.push_back(texture);  // store it as texture loaded for entire model, to ensure we won't unnecesery load duplicate textures.
            }
        }
    }
    return textures;
}





void Model::SetVertexBoneDataToDefault(Vertex& vertex)
{
    for (int i = 0; i < MAX_BONE_INFLUENCE; i++)
    {
        vertex.m_BoneIDs[i] = -1;
        vertex.m_Weights[i] = 0.0f;
    }
}


void Model::SetVertexBoneData(Vertex& vertex, int boneID, float weight)
{
    for (int i = 0; i < MAX_BONE_INFLUENCE; ++i)
    {
        if (vertex.m_BoneIDs[i] < 0)
        {
            vertex.m_Weights[i] = weight;
            vertex.m_BoneIDs[i] = boneID;
            break;
        }
    }
}


void Model::ExtractBoneWeightForVertices(std::vector<Vertex>& vertices, aiMesh* mesh, const aiScene* scene)
{
    auto& boneInfoMap = m_BoneInfoMap;
    int& boneCount = m_BoneCounter;

    for (int boneIndex = 0; boneIndex < mesh->mNumBones; ++boneIndex)
    {
        int boneID = -1;
        std::string boneName = mesh->mBones[boneIndex]->mName.C_Str();
        if (boneInfoMap.find(boneName) == boneInfoMap.end())
        {
            BoneInfo newBoneInfo;
            newBoneInfo.id = boneCount;
            newBoneInfo.offset = AssimpGLMHelpers::ConvertMatrixToGLMFormat(mesh->mBones[boneIndex]->mOffsetMatrix);
            boneInfoMap[boneName] = newBoneInfo;
            boneID = boneCount;
            boneCount++;
        }
        else
        {
            boneID = boneInfoMap[boneName].id;
        }
        assert(boneID != -1);
        auto weights = mesh->mBones[boneIndex]->mWeights;
        int numWeights = mesh->mBones[boneIndex]->mNumWeights;

        for (int weightIndex = 0; weightIndex < numWeights; ++weightIndex)
        {
            int vertexId = weights[weightIndex].mVertexId;
            float weight = weights[weightIndex].mWeight;
            assert(vertexId <= vertices.size());
            SetVertexBoneData(vertices[vertexId], boneID, weight);
        }
    }
}