Parallel to surface means that the cuts of on your drive surface will be generated parallel to a check surface. Especially when your drive surface comes across with a very uneven check surface this option is very helpful.
Select "parallel to surface" and hit the "single edge" button. Then pick the check surface you want to make the parallel cuts from.
It’s important to activate the gouge check, to make sure that the check surface won’t be destroyed. The selected" single edge" surface is your check surface in the gouge check.
Here you can see the tool running on the drive surface parallel to the wavy check surface. All cuts are parallel, it does not matter how far they are away from the check surface.
You also have the opportunity to work with margins. This is the same as in Morph between two surfaces. The tool has to be a sphere mill and Calc. based on tool center in the Utility tab must be enabled.
