Atmosphere works all wrong

What you describe is working like that by design. (light gas moving up and left, gases taking a long while to balance out). The idea behind it is (most likely) to have easy transition rules for every gas combination by only looking at one cell and its immediate neighbours. The less cells, you need to look at, the better the performance.

The movements are also not instant, because ONI is tile-based and tick-based. So every gas movement you see is just another step towards a stable state (light in upper left, heavy in lower right).

 

What happened in your scenario:

1) oxygen entered through mesh tiles.

2) oxygen is checked to neighbouring fields (simplified)

2.1) if neightbours are oxygen, stay where you are

2.2) if neighbours hydrogen, move down/right

3) rince repeat

Likewise hydrogen will move up and left if meeting oxygen.

 

By this logic you will quickly end up with your diagonal gas distribution.

So this does not seem like a bug to report, but a concept to discuss. You are surely not the only one, who would prefer a gravity-esque concept.

Edited June 3, 2018 by blash365

actually you can remove the skewed distribution quite easy and without any performance impact... it may not totally flatten horizontally but it would be much better than now...

 

all you have to do is:

even sim steps: do what you do now

odd sim steps: mirrored logic (topright light, bottom left heavy)

 

it's more code but it will just compensate that unatural skew you see now...