Intro
I expected negative values for LineThickness to not be allowed; however, it appears they are tolerated for whatever reason. Negative values behave very strangely and I’m not sure if it was intentionally designed to be this way.
Apparently, setting the LineThickness to: -(0.1)n, where n is a positive integer, it appears that
the selectionbox renders at roughly: 150n studs away from the camera.
This is not limited to the studio camera, the same effects are shown in a live game.
repro.rbxl (18.5 KB)
Repro
1. Insert part with a SelectionBox
2. Set Adornee to said part
3. Set LineThickness to -0.1
4. Move the camera roughly 150 studs away (or more), and the selectionbox will render
These steps reproduce the issue 100% of the time, regardless of the place of time of reproduction.
Images from repro file in studio: