If I were to have a bunch of invisible parts, how would it affect performance compared to if they were visible? I’d like to add LOD in my game where things that are further away are turned invisible or swapped with lower quality models.
If I remember correctly 1 transparency completely removes the part from the rendering pipeline.
And then making them non-collide would disable the physics?
Sorta. It’ll prevent some math from being done but not completely.
Transparency 1 has best performance, transparency 0 after that, and anything between 0-1 is worse. (Rendering-wise, obviously. Parts still take memory and there may still be physics simulation with these parts on the CPU)
Parenting things in/out of the game hierarchy makes it so that data structures related to physics have to be updated among other tasks, so this is not free. Just try both solutions and see which works best.
Problem with LOD systems is that removing or making parts transparent means there must be lighting updates, which can cause frame drops when things are constantly changing. These usually make it pointless or worse having an LOD system, unless you can find a way around this. If you do, I would really like to know how. Good luck though!
Invisible parts have minimal to no impact on performance, just worry about the physics associated with your game (i.e. if a bullet needs to pass that invisible part).