Michael,

what I mean by relatively large is this 1 x 10-3 compared with something like 4.9406564584124654 x 10−324 (Double floating-point).

But I also understand the constraint with what you added below.

->Various different processes need to carry out their calculations until they reach a particular accuracy level which they can then judge to be good enough. If that accuracy level is
-> set to be too high, then those processes will both take a lot of extra time and also generate much more dense results for things like intersection curve results, etc...


->I am generally moving things towards a system that uses a relative fraction of the object's bounding size rather than a fixed tolerance size though. But that can still be
->problematic when you've got just some little tiny portion of the object being a small size.

Maybe, just maybe it would be possible to have something like an on-demand tolerance control. I'm sure a 0.001 is "small" enough in most case but as you well know there are exceptions and in those cases it would be nice to have a say in specific situations but not overal say like the mesh angle parameter work. For example, we know with the ring file I provided, scaling things up made union work, I even scaled it back 1/10 and it was fine, then I suppose that lowering the tolerance could also work in this particular case. I tried this same approach on something else and it didn't work, which brings up the question of feedback, especially when a command fails to give us a result but I know this is complicated as well, maybe even more then this tolerance thing.

***
If you're unioning a whole lot of things together in one pass you may also get some better results by only selecting 2 pieces at a time - sometimes union can have some additional difficulty if you've selected some large number of separate pieces and it happens to process some pairs that do not actually touch each other first. It will try to sort things so that if you have one large object and a bunch of small ones touching it, that it will do the large one first so they'll all be intersecting but if you have a whole lot of daisy-chained type same size pieces you may need to select them 2 at time, at least that's worth a try if you run into a problem.
***

Though this approach is fine when only a few objects are in play but in practice for my flower "middle" part for example (100+ spheres), I migth as well think of a totally different approach to create them and most likely not in Moi unfortunatly.


As for the group mechanism, I'm very happy to see it will be there at some point.

Thanks,
Felix