I need help trying to create piping that goes along a curved surface for half of it, then curves out away from the surface Not sure if my explanation makes sense. I'm making a 3D model of the Titanic, and for most of the Smokestack piping I've been using the shrinkwrap modifier to attach curves to the smokestack, but the No. 3 Smokestack has piping that juts out to the Tank Room.



If I use the shrinkwrap modifier, the parts of the pipe that jut out will just stick to the smokestack. I could have the piping in two pieces (one shrinkwrapped the other not) but I was wondering if there was any way to have it all in one piece (maybe even learn a new way to have the piping sit on the curved surface).
Perhaps an alternative approach to shrinkwrapping is as follows: (It's not easy to make illustrations for this one, so I'll just try to decscribe it)


Duplicate your smokestack and tanks
Enlarge the duplicate appropriately, scaling (S) or fattening (AltS). This object is going to be the 'Form' for your pipes (they lie slightly outside the objects they are aligned to.)
Simply select edges from the 'Form', where you want the pipes on the cylinder. Don't worry about the right-angle corners, we'll get to that. If the edges don't exist, subdivide, or cut using the Knife (K) tool.
Duplicate (ShiftD) those edges, and extrude the end vertices of the duplicate sections to create the splaying straight pipes. If your model is up in Z, that will be - Select vertex, EShiftZ for the horizontal sections, and EZ for the plunge into the tank.
Separate the selection of edges (P) into a new 'Pipes' object - and bevel (CtrlShiftB) its right-angle corner vertices to give them the curve you're looking for.
Convert the 'Pipes' mesh into a Curve, and in its'Shape' and 'Geometry' panels give it a Full Bevel profile with enough resolution to make the pipes round.
If you've kept the resolutions reasonable , and dissolved out vertices in straight sections which are not contributing to the shape, you might want convert back to mesh, and put a subdivision surface modifier on the result.




I short, the method takes the vertices from existing geometry, rather than creating shapes from scratch.