(related to “Form1+ Rocking it” comments…)
I am testing out manual support creation using a known solid from TinkerCAD (spiral shape). But I have seen this issue with other more complex STLs.
Basically though I click on the underside of a part of the geometry and the support is created, it does not affect the shading (even after shading regeneration). When I inspect closely I find that the support stop short of touching the geometry at the top. If I just keep deleting and readding in the same area, eventually I get one that touches. Have not figured out what the sensitivity is yet, because sometimes it always works and other times it is hit and miss. Maybe it is an issue with thinner (but closed) geometry?
You can see from the pic below that the support at far left does not touch the geometry. I created and then deleted a number of these and have the sense that creating them closer in to the center of the spiral where the wall is not so thin works ok. Seems that beyond a certain thinness the support does not find the surface at the top.