The whole "disbelieve" thing comes from 2E, maybe earlier. Back then you could pretty much choose to disbelieve anything so long as you said, "I disbelieve."
It's different in 3E. You have to actually have a basis (interaction) for disbelief in 3E and the save is a result of the interaction.
No.Rules are rules. Its an illusion/glammer. If someone interacts with an invisible thing thru hitting the 50% miss, seing a fire ball go of and the tell tail gap etc then a save is in order.
The saving throw in case of invisibility is for the target of the illusion, in this case the person or object to become invisible, NOT the one's (not) seeing the illusion.Seems it has a target, it gets a save (harnmless) as it doesn't damage.
It's magicMy question is if it cannot reproduce real effects and isn't a divination how can I cast it on a door and see the entire contents of a room as if the real door was not there......

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.