Similar questions have come up, but they were all several years ago, so I'm hoping there's been some change. My perspective is also a little different since I don't want to manipulate Vuforia's parameters but merely read its mind.
I'd like to be able to inspect a confidence or target-correlation value for a currently tracked target. My situation and use case follows:
Vuforia is providing camera position and/or relative object position for a number of targets in several different applications I'm working on. As tracking is lost on a target, the inserted artwork almost invariably has, perhaps, 1-2 frames of "crazy" where orientation goes nuts. It's just an instant, but it takes an otherwise smooth presentation and makes it look very WIP. I would prefer if during those frames that *tracking* continue (to maintain the target as active and continue trying to track it) but to be able to hide the inserted artwork. I don't expect Vuforia to provide that - just the information to make it happen.
I know I could place limits on per-frame rotational magnitude and possibly get close to what I want (that's what I'm experimenting with now), but it seems likely that the underlying engine knows it's not a great frame. Being able to watch for confidence spikes would be helpful - if confidence drops by half in a single frame, it's quite likely that's not a great frame.
Basically, I'd rather have my augmentation disappear or remain stuck in the previous pose rather than follow a whacky new orientation. Exposing some information about feature presence and confidence would help this along. I don't want Vuforia to stop tracking the target - if confidence returns or at least stabilizes, I'd want the augmentation to bounce back in - but I want a way to monitor how good the target is to control some behaviors myself.