A follower VTool can follow raster geometry to vectorize it, but prompts you for input when it reaches a decision point, where it can no longer proceed on its own (for instance, at a raster endpoint or a label). At each decision point, you can provide more information, change course, return to a previous vertex, or stop the follower. AutoCAD Raster Design toolset provides follower tools for vectorizing polylines. For more information, see Vector Follower Tools.