[boskid][2.1.8] Legendary Inserter has inconsistent rotation times

[AkaraVortex]

Latest 2.1.8 changes has affected Legendary Inserter's rotation times from consistent 8 ticks per cycle into inconsistent 8/9 ticks depending on swing direction.

I will explain this on maxed out Legendary Stack Inserter (4 stacks of size 4).

For chest-to-chest movement:
If it is horizontal, then all is as intended - 8 ticks per cycle (4 ticks for forward movement, and 4 ticks backward). But vertical one alternates between 8 ticks for left-sided rotation (4+4) and 9 for right-sided one (5+4 if looking up, 4+5 if looking down), meaning it takes 1 tick longer to travel every second cycle when swinging from right side upwards (counterclockwise).
You can easily test if for yourself by pasting in editor chest-to-chest inserters for all 4 rotations side by side, and seeing them desync almost instantly. Example below:

inserter_inconsistency.mp4

(14.44 MiB) Downloaded 18 times

inserter_inconsistency.gif (15.59 MiB) Viewed 10366 times

Exactly same for chest-to-belt and belt-to-chest movement, just with some extra amount of ticks in the middle depending on stack size and pick conditions.

Lower quality inserters do not see such issue, they have consistent swing cycle times.
I do not need to explain how devastating it is - it drops throughput from 120 to ~113 for chest-to-chest and from 80 to ~76 for chest-to-belt, which ruins a lot of builds and ratios. Secondary it breaks all clocked builds which do tick-perfect output, not only by changing the active window duration, but making it alternate uncontrollably.
And finally it is exact opposite of what 2.1.8 fix wanted to do - consistent swing times regardless of rotation or mirroring, which is right call, but current version is anything but for legendary inserter, admittedly the only quality inserter for all megabasers.

I really do hope that will be fixed to what it was before, please, Wube.

[eugenekay]

134293?

Can you share a testbed save please? I am putting one together myself to measure the tick times across versions, because this sounds interesting.

[AkaraVortex]

Yes, but since it was rejected for not being technical enough, i decided to make a post with exact details on the issue.

Here is the test map with display clock, switch and 3 cases with 4 directions to see it:

Test.zip

(1.06 MiB) Downloaded 14 times

Reply to previous post was indicating that this is insignificant, but for my base it literally breaks all builds, because they are all clocked.

[vmainen]

Definitely seems like a problem that needs to be fixed. Veteran players remember when direction of the rails decided how many inserters would fit per train cart, but a great effort has been taken by the devs to remove these kinds of quirks. I think the inserter swinging has been tweaked too over the years.

[Techjar]

I can also add to this issue, it's messing up any setup I have that uses 2 legendary stack inserters to fill a belt lane. It seems like the timings are a bit off so the inserter ends up leaving gaps where it doesn't swing over the belt in time. They do seem ever so slightly slower visually as well, but not sure if that's just a placebo.

I made a simple blueprint to test it:

Code: Select all

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Here's how it looked on 2.1.7 and earlier:


And here's what happens on 2.1.8:


This does in fact only occur with vertical inserters. If I paste the blueprint rotated so the inserters are horizontal, it works fine and has no gaps like the 2.1.7 image.

[boskid]

Thanks for the report. Issue is now fixed for 2.1.9.

This was quite tough issue because it involves floating point math errors that were accumulating differently based on inserter orientation, so i had to change inserters logic to use fixed point orientations to make their behavior symmetric in all cases. Additional problems were caused by the fact, that legendary stack inserters based on the tooltip values (2160deg/s rotation) were supposed to take 5 ticks to rotate from chest to chest, however they were only taking 4 ticks because of the same floating point math errors since after 4 ticks the inserter hand was close enough to a target that it was snapping causing one update tick to be skipped. There was quite a lot of decision making here but we decided that this bug (legendary stack inserter taking only 4 ticks to rotate 180deg) will become a feature so i also had to make sure that this behavior is preserved and covered by tests.

[Zukulini]

Excellent! That's just the fix I was hoping this issue would get, thanks for your awesome work.

[berggen]

Thanks for the report. Issue is now fixed for 2.1.9.

This was quite tough issue because it involves floating point math errors that were accumulating differently based on inserter orientation, so i had to change inserters logic to use fixed point orientations to make their behavior symmetric in all cases. Additional problems were caused by the fact, that legendary stack inserters based on the tooltip values (2160deg/s rotation) were supposed to take 5 ticks to rotate from chest to chest, however they were only taking 4 ticks because of the same floating point math errors since after 4 ticks the inserter hand was close enough to a target that it was snapping causing one update tick to be skipped. There was quite a lot of decision making here but we decided that this bug (legendary stack inserter taking only 4 ticks to rotate 180deg) will become a feature so i also had to make sure that this behavior is preserved and covered by tests.

The floating point errors accumulated slightly differently for a legendary quick+ inserter than for a normal long handed inserter. Does this change mean that long-handed inserters now also get the round down benefit, bringing their swing to 24 ticks instead of 25?

[boskid]

Normal quality long handed inserter in 2.0.77 took 25 ticks to rotate 180 from chest to chest. I measured normal quality long handed inserters with this fix and they are indeed faster taking only 24 ticks.