3D model vertex normals are now calculated in parallel

    m_PerFaceVertexNormals.clear();

    // Pre-allocate space for the entire vector of vertex normals so we can do parallel writes

    m_PerFaceVertexNormals.resize(m_CoordIndex.size());

    // for each face A in mesh

    #pragma omp parallel for

    for( unsigned int each_face_A_idx = 0; each_face_A_idx < m_CoordIndex.size(); each_face_A_idx++ )

    {

        // n = face A facet normal

        std::vector< glm::vec3 > face_A_normals;

        face_A_normals.clear();

        std::vector< glm::vec3 >& face_A_normals = m_PerFaceVertexNormals[each_face_A_idx];

        face_A_normals.resize(m_CoordIndex[each_face_A_idx].size());

        // loop through all 3 vertices

            }

        }

        m_PerFaceVertexNormals.push_back( face_A_normals );

    }

}