Method ProcessMesh

code/PostProcessing/CalcTangentsProcess.cpp:103–299

------------------------------------------------------------------------------------------------ Calculates tangents and bi-tangents for the given mesh

// ------------------------------------------------------------------------------------------------
// Calculates tangents and bi-tangents for the given mesh
bool CalcTangentsProcess::ProcessMesh(aiMesh *pMesh, unsigned int meshIndex) {
    // we assume that the mesh is still in the verbose vertex format where each face has its own set
    // of vertices and no vertices are shared between faces. Sadly I don't know any quick test to
    // assert() it here.
    // assert( must be verbose, dammit);

    if (pMesh->mTangents) // this implies that mBitangents is also there
        return false;

    // If the mesh consists of lines and/or points but not of
    // triangles or higher-order polygons the normal vectors
    // are undefined.
    if (!(pMesh->mPrimitiveTypes & (aiPrimitiveType_TRIANGLE | aiPrimitiveType_POLYGON))) {
        ASSIMP_LOG_INFO("Tangents are undefined for line and point meshes");
        return false;
    }

    // what we can check, though, is if the mesh has normals and texture coordinates. That's a requirement
    if (pMesh->mNormals == nullptr) {
        ASSIMP_LOG_ERROR("Failed to compute tangents; need normals");
        return false;
    }
    if (configSourceUV >= AI_MAX_NUMBER_OF_TEXTURECOORDS || !pMesh->mTextureCoords[configSourceUV]) {
        ASSIMP_LOG_ERROR("Failed to compute tangents; need UV data in channel", configSourceUV);
        return false;
    }

    const float angleEpsilon = 0.9999f;

    std::vector<bool> vertexDone(pMesh->mNumVertices, false);
    const float qnan = get_qnan();

    // create space for the tangents and bitangents
    pMesh->mTangents = new aiVector3D[pMesh->mNumVertices];
    pMesh->mBitangents = new aiVector3D[pMesh->mNumVertices];

    const aiVector3D *meshPos = pMesh->mVertices;
    const aiVector3D *meshNorm = pMesh->mNormals;
    const aiVector3D *meshTex = pMesh->mTextureCoords[configSourceUV];
    aiVector3D *meshTang = pMesh->mTangents;
    aiVector3D *meshBitang = pMesh->mBitangents;

    // calculate the tangent and bitangent for every face
    for (unsigned int a = 0; a < pMesh->mNumFaces; a++) {
        const aiFace &face = pMesh->mFaces[a];
        if (face.mNumIndices < 3) {
            // There are less than three indices, thus the tangent vector
            // is not defined. We are finished with these vertices now,
            // their tangent vectors are set to qnan.
            for (unsigned int i = 0; i < face.mNumIndices; ++i) {
                unsigned int idx = face.mIndices[i];
                vertexDone[idx] = true;
                meshTang[idx] = aiVector3D(qnan);
                meshBitang[idx] = aiVector3D(qnan);
            }

            continue;
        }