Playing with 4.0.4, noticed that the 3d viewer fails to display the board properly if there’s a line routed on the PCB which does not form a closed path. I used such feature on one of my PCBs as a cable retainer, and it was drawn with line width equal to the mill diameter which didn’t require the tool to follow a closed path, just a simple slot cut-out.
Should it be considered as a bug in the viewer?
Think about it…
You define closed path outlines on that very same layer for a tool to pass along on it’s perimeter.
If you want to define slot cuts with line thicknesses you have to define them on a different layer - User.Dwgs or EcoX come to mind - and then you have to communicate that with your fab when you give them the gerbers.
Your post have inspired me to verify how it’s done on production gerbers (my EMS is building up panels, based on my Gerbers). The slot is converted into a path on slot’s perimeter.
I have updated my board to have a slot routed this way, and the 3d view is OK now 
1 Like