3.1.2 Mesh::loadModel()

For full code, please move directly to the end of this page

Use Assimp to load models

In Mesh.cpp, write your loadModel function.

We are not using the hierarchical scene graph of Assimp at the moment, we only read the meshes in the Scene node.

    Assimp::Importer importer;
    const aiScene* scene = importer.ReadFile(path, aiProcess_CalcTangentSpace);
    if (NULL != scene) {
        std::cout << "load model successful" << std::endl;
    } else {
        std::cout << "load model failed" << std::endl;
    }

    // mNumMeshes should > 0
    //std::cout << scene->mNumMeshes << std::endl;

Assimp Scene graph

Read vertex and triangle data

We are going to read Assimp mesh data to our buffer in a loop

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

First read vertex position and normals (we don't deal with texture at the moment)

        // read vertex position and normals
        int nVertex = mesh->mNumVertices;
        for (int j = 0; j < nVertex; j++)
        {
            glm::vec3 pos; 
            pos.x = mesh->mVertices[j].x;
            pos.y = mesh->mVertices[j].y;
            pos.z = mesh->mVertices[j].z; 

            glm::vec3 normal;
            normal.x = mesh->mNormals[j].x;
            normal.y = mesh->mNormals[j].y;
            normal.z = mesh->mNormals[j].z;

            normals.push_back(normal);
        }

Then read triangle indices

	int nFaces = mesh->mNumFaces;
        for (int j = 0; j < nFaces; j++ )
        {
            const aiFace& face = mesh->mFaces[j];
            for (int k = 0; k < 3; k++)
            {
                indices.push_back(face.mIndices[k]);
            }
        }

Full Source Code

void Mesh::loadModel(std::string path) 
{
    Assimp::Importer importer;
    const aiScene* scene = importer.ReadFile(path, aiProcess_JoinIdenticalVertices);
    if (NULL != scene) {
        std::cout << "load model successful" << std::endl;
    } else {
        std::cout << "load model failed" << std::endl;
    }

    // mNumMeshes should > 0
    // std::cout << scene->mNumMeshes << std::endl;

    // at the moment we only handle one mesh
    for (int i = 0; i < scene->mNumMeshes; i++)
    {
        aiMesh* mesh = scene->mMeshes[i];
        
        // read vertex position and normals
        int nVertex = mesh->mNumVertices;
        // std::cout << mesh->mNumVertices << std::endl;
        for (int j = 0; j < nVertex; j++)
        {
            glm::vec3 pos; 
            pos.x = mesh->mVertices[j].x;
            pos.y = mesh->mVertices[j].y;
            pos.z = mesh->mVertices[j].z; 
            vertices.push_back(pos);

            glm::vec3 normal;
            normal.x = mesh->mNormals[j].x;
            normal.y = mesh->mNormals[j].y;
            normal.z = mesh->mNormals[j].z;
            vertices.push_back(normal);

        }

		int nFaces = mesh->mNumFaces;
        for (int j = 0; j < nFaces; j++ )
        {
            const aiFace& face = mesh->mFaces[j];
            for (int k = 0; k < 3; k++)
            {
                indices.push_back(face.mIndices[k]); 

            }
        }
    }
}