More complex physical models join computational fluid dynamics models with a wildland fire component and allow the fire to feed back upon the atmosphere. These models include NCAR 's Coupled Atmosphere-Wildland Fire-Environment (CAWFE) model developed in 2005, WRF-Fire at NCAR and University of Colorado Denver which combines the Weather Research and Forecasting Model with a spread model by the level-set method, University of Utah 's Coupled Atmosphere-Wildland Fire Large Eddy Simulation developed in 2009, Los Alamos National Laboratory's FIRETEC developed in, the WUI (wildland–urban interface) Fire Dynamics Simulator (WFDS) developed in 2007, and, to some degree, the two-dimensional model FIRESTAR. These tools have different emphases and have been applied to better understand the fundamental aspects of fire behavior, such as fuel inhomogeneities on fire behavior, feedbacks between the fire and the atmospheric environment as the basis for the universal fire shape, and are beginning to be applied to wildland urban interface house-to-house fire spread at the community-scale.