2603 20160701171707.0 ASTROimport-760 Lobel, A. 2007 Three dimensional radiative transfer in winds of massive stars: Wind3D Radiative transfer calculations in three dimensions are presented to investigate dynamic structures in extended winds of massive stars. We discuss the development of the new radiative transfer code Wind3D. It solves the non-LTE radiative transport problem in moving stellar atmosphere models in three geometric dimensions. The code accepts arbitrary 3D velocity fields in Cartesian geometry without assumptions of axial symmetry. Wind3D is currently implemented as a fully parallelized (exact) accelerated lambda iter- ation scheme with a two level atom formulation. The numerical transfer scheme is efficient and very accurate to trace small variations of local velocity gradients on line opacity in strongly scattering dominated extended stellar winds. We in- vestigate the detailed formation of P Cygni line profiles observed in ultraviolet spectra of massive stars. We compute the detailed shape of these resonance lines to model local enhancements of line opacity that can for instance be caused by clumping in supersonically expanding winds. Wind3D will be applied to hy- drodynamic models to investigate physical properties of discrete absorption line components. Blomme, R. UV Astronomy: Stars from Birth to Death 2007 119 http://esoads.eso.org/abs/2007uasb.conf..119L published in NONREF