Generating principal stress lines over a shell surface and selecting the most significant ones to define a gridshell topology have been the primary goal of numerous studies on mechanical streamlines. This research introduces a novel typology of mechanical lines: eccentricity lines, based on the R-Funicularity principle [1], which synthesize principal stress and bending moments through the evaluation of generalized eccentricity. This study proposes a method to evaluate generalized eccentricity, plot eccentricity lines on continuous shells, and regularize them using a custom Grasshopper 3D script. The versatility and efficiency of Grasshopper scripts in managing complex geometries make it a valuable tool in this process. Grasshopper was selected due to its capability to enable parametric form definition, analysis, and the generation of multiple line families within a single environment. To validate the proposed method, different shell structure examples will be analyzed. These case studies will test the effectiveness of the method in different scenarios, investigating how eccentricity lines could be used to enhance both structural integrity and aesthetic appeal. Furthermore, the potential future applications of eccentricity lines in shell structures will be discussed. This research underscores the importance of integrating computational tools in structural design to achieve a synthesis of form and function, paving the way for structurally inspired designs that meet both engineering and architectural aspirations.