Radiative Transfer in 3D

The high resolution and sensitivity provided by proposed Atacama Large Millimeter Array will reveal new small scale structures in many sources, e.g. star forming regions. Such inhomogeneities may not have been considered in the analysis of past observations but they will be essential to the understanding of future data. Radiative transfer methods are needed to interpret the observations and the presence of complicated source structures and small scale inhomogeneities requires 3D modelling. We will describe studies of molecular line emission we have made using models of inhomogeneous molecular clouds. These are based on MHD models and include e.g. thermal balance calculations for molecular clouds.