Extracting isolines

- If you zoom in to the seat post tube,…you'll see that it's paper thin.…We need to represent this tube with some real thickness,…and there's actually another layer…which show this thickness.…Let's go up to the Home tab here…under Layers and choose Unisolate, then Isolate,…and select these objects.…This light blue color layer has…this inner surface of the tube.…Go over to the Surface tab and choose Offset.…

Select the yellow surface, enter,…and there are white arrows representing…the normals to the surface, that is vectors…that point perpendicular to the surface,…and they give you a visual indication of which way…you'll be offsetting the surface, in this case outward.…Now I don't want that, I want the surface to go inward…so I need to change the direction.…Use the Flip Direction option,…and the arrows now point inward.…Now it says, "Specify Offset Distance."…That's going to be the distance…from this point to this point.…

So just using Object Snap allows me…to visually click those two points…without having to worry about the numeric value.…