This tutorial uses subdivision modelling to model a hollow object.
This shows the bumper of the car modelled using both subdivision modelling and parametric modelling. Note the differences.
To make something hollow, DELETE FACES and add a SOLIDIFY MODIFIER but -if you want to use Boxcutter-, only:
– after you have finished the overall shape and are happy with the result, and
– after you have divided your (still manifold) object into (still manifold) slices.
…or just switch to Boxcutter knife project or go into edit mode and use knife cut or anything really and party on).
Rule #1: Do not extrude, [ESC], scale inward (ever!) to make hollow. Go sit in the naughty corner.
Rule #2: Don’t delete faces and then use basic boxcutter cuts/slices. Manifold Mesh Only. No Holes!
How not to make a window:
– Slice cut a window into a cube, slap on a glass material and voila, no window because cube is not hollow.
How to make a window:
– Separate faces, solidify and apply glass material. Then, make your skin-only main object-with-a-hole-in-it (= non-manifold) hollow and manifold again by applying a solidify modifier.
Use solidify late in the process to give a (non-manifold) object thickness and make a hollow manifold object.
Non-manifold = does not hold water = has no volume = skin with holes = use knife project or edit mode, not booleans.