TL;DRInserters care about the direction of a belt on which they try to place things. I don't think they should.
BackgroundI first reported this as a bug, because I thought it only applied to underground belts, but as it turns out, the "bug" was in fact the lack of a feature which I just assumed was in there but wasn't.
I've thought that inserters always placed on belts relative to the inserter, i.e. that it would always place in the quadrant opposite and to the right.
This rule-of-thumb holds true for a majority of cases, but there are a couple of exceptions. I've included a picture of every (?) possible combination of inserter direction and belt type.
In the figure, A1, B1, C1, E1, E3, F2, G4, H3, J2 and J4 show signs of disobeying the rule.
In these cases, it seems the inserter is aware of the direction of the belt when placing, which contradicts the general appearance of inserters as mechanical entities.
Notice for instance how the items in D1 and C1 end up in different lanes, despite being almost identical setups.
What?I want inserters to place items predictably, relative to their own reference frame only, preferably in the front right corner of their target square.
Why?Planning more advanced setups is easier if there is an easy way to remember/predict where items will be deposited.
The use case that got me onto this track was two inserters facing opposite ways placing onto the entrance and exit of an underground belt respectively, where a consistent behaviour would make them deposit on one lane each.