In recent years, several techniques have been proposed for automatically producing line-art illustrations. In this paper a new non photo-realistic rendering scheme for triangulated surfaces is presented. In contrast to prior approaches with parametric surfaces, there is no global parameterization for triangle meshes. So a new approach is made to automatically generate a direction field for the strokes. Discrete curvature analysis on such meshes allows to estimate differential parameters. Lines of curvature are then constructed to be used as strokes. Using triangulated surfaces allows to render aesthetically pleasing line drawings from a huge class of models. Besides, experiments show that even real time visualization is possible.