Simulation is a powerful tool to optimize composites materials forming. Both dry fabric forming and resin flow can be simulated using fabric unit cell models. With the aim of performing analyses of the mechanical behaviour at the mesoscopic scale, an accurate geometrical model of the fabric unit cell has to be defined and meshed. Defining the geometry on which this meshing is applied is a difficult and important point. In order to determine yarn geometry for different cases of yarn structure and weave patterns, experimental observations using different optical processes have been performed. The analysis of these results helps us define an accurate 3D model of the woven yarn shape. Using this yarn model, a consistent 3D geometrical model of fabrics is presented. This model ensures an accurate contact between yarns. It is called consistent because penetrations and spurious voids between warp and weft yarns are avoided. The yarn section shape varies along the trajectory, so that the influence of contact between yarns on their cross-section shape can be taken into account. A meshing preprocessor based on this geometrical model is then developed. This is an important point for 3D finite element simulation of fabrics, which is a powerful method to investigate mechanical behaviour. A consistent geometry of the fabric at the deformed state can also be obtained and used to define the influence of deformation on resin flow.