I’m running into a problem using Retopo. When retopo is applied to selected vertices they do indeed take the shape of the background mesh. However, they don’t stop at the background mesh; they project through and beyond, stopping eventually.
The screen shot below is the result after applying retopo to the bottom ring of vertices on a cylinder. You can see that they conform to the shape of the background mesh, but they are projected through and don’t land on the background mesh itself:
The .blend is at http://www.skwerm.com/blender/retopo.blend
Thanks for any help!