private:
// loads a model with supported ASSIMP extensions from file and stores the resulting meshes in the meshes vector.
void loadModel(string const& path)
{
// read file via ASSIMP
Assimp::Importer importer;
const aiScene* scene = importer.ReadFile(path, aiProcess_Triangulate | aiProcess_GenSmoothNormals | aiProcess_FlipUVs | aiProcess_CalcTangentSpace);
// check for errors
if (!scene || scene->mFlags & AI_SCENE_FLAGS_INCOMPLETE || !scene->mRootNode) // if is Not Zero
{
cout << "ERROR::ASSIMP:: " << importer.GetErrorString() << endl;
return;
}
// retrieve the directory path of the filepath
directory = path.substr(0, path.find_last_of('/'));
// 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 processNode(aiNode* node, const aiScene* scene)
{
// 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 processMesh(aiMesh* mesh, const aiScene* scene)
{
// data to fill
vector<Vertex> vertices;
vector<unsigned int> indices;
vector<Texture> 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.
// positions
vector.x = mesh->mVertices[i].x;
vector.y = mesh->mVertices[i].y;
vector.z = mesh->mVertices[i].z;
vertex.Position = vector;
// 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;
vec.y = mesh->mTextureCoords[0][i].y;
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<Texture> diffuseMaps = loadMaterialTextures(material, aiTextureType_DIFFUSE, "texture_diffuse");
textures.insert(textures.end(), diffuseMaps.begin(), diffuseMaps.end());
// 2. specular maps
vector<Texture> specularMaps = loadMaterialTextures(material, aiTextureType_SPECULAR, "texture_specular");
textures.insert(textures.end(), specularMaps.begin(), specularMaps.end());
// 3. normal maps
std::vector<Texture> normalMaps = loadMaterialTextures(material, aiTextureType_HEIGHT, "texture_normal");
textures.insert(textures.end(), normalMaps.begin(), normalMaps.end());
// 4. height maps
std::vector<Texture> heightMaps = loadMaterialTextures(material, aiTextureType_AMBIENT, "texture_height");
textures.insert(textures.end(), heightMaps.begin(), heightMaps.end());
// 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<Texture> 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);
// 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
Texture texture;
texture.id = TextureFromFile(str.C_Str(), this->directory);
texture.type = typeName;
texture.path = str.C_Str();
textures.push_back(texture);
textures_loaded.push_back(texture); // store it as texture loaded for entire model, to ensure we won't unnecessary load duplicate textures.
}
}
return textures;
}
