The problem is that you are taking the definition of “Layer” from other software and trying to apply it to SU: The term “Layer” in SU refers to a viewing plane.
Each entity - edge, face, group or component - can be assigned to a different layer. HOWEVER the visibility status is not determined by the wrapper object’s visibility:
Example: model of a car…
Bodywork, Windsheild & Lights are elements inside Exterior Group
Axle, Engine & Wheels are inside Interior Group
Interior and Exterior are part of Car Model
- Everything starts on Layer0
- If I assign Car Model to LayerA and turn it’s visibility off, everything vanishes.
- If I turn it back on and set Interior onto LayerB, then turn off it’s visibility, then the Axle, Engine and Wheels vanish.
- If I leave this off and turn LaterA off, everything vanishes again. If I turn back on LayerA, you have a floating car; you only see the Bodywork, Windsheild & Lights. This is the key to it all: The LayerA controls the visibility of the Car Model, but when you toggle it, you can’t see all of the car because parts of it are on a hidden layer.
- One entity can have it’s visibility turned off by many different layers; for example the hub-cap of the wheel can be on it’s own layer, as can the wheel, as can the interior, as can the main model - all 4 layers must be visible before you can see/edit the hubcap entity. If one of them is turned off, it’s gone.
Now you add complications like another layer and mix up which nested level of groups and objects are assigned to it… Unless you are very organised and understand how the layering works, it is really easy to get confused. If you add in the ability that each of these can also be hidden rather than completely turned off, it adds another layer of complexity (pun intended).
Oh, and all of these options only hide the geometry from view - it’s still there and if you try and delete a line or move an edge or draw a surface that would alter the hidden geometry, it still will change it.