Lateral spatial resolution is a particularly challenging concept to quantify in triangulation-based 3D imaging systems. In this paper, we present these challenges, then describe an artifact-based methodology for evaluating the lateral resolution of a triangulation-based 3D imaging system that uses laser spots or laser lines. In particular, the response of a 3D imaging system to a spatial discontinuity (step edge) has traditionally been modelled as a first-order linear system. We model the response of a triangulation-based laser imaging system to a spatial step edge from first principles and demonstrate that the response should be modelled as a non-linear system. This model is then used as a basis for evaluating the lateral (structural) resolution of a triangulation-based laser imaging system.