I'm currently writing on a SDI plotting application which reads and displays a BRep file and plots different views. The user may create different views onto the CAD model, therefore for each view the ViewMapping and ViewOrientation are saved. From the different views I want to create a Print Preview where the user can interactively place and move the different views. To Draw the Print Preview I think I have to vectorise the TopoDS_Shape (BRep file) into 3D Line segments and project those line segments into the viewport. The viewport coordinates can then be used to create the Print Preview. The problem is that I have no guess how I can vectorise the TopoDS_Shape. A few hints would be great!