[2.1.7] Tree farm pollution mitigation broken

[stupidfathobbit]

Full discovery and diagnosis of problem (a bit long but quite thorough): https://youtu.be/MVUVfx4zQmg?t=11720

Seems like something broke with trees taking damage from pollution. Noticed the issue in 2.1.7 with my migrated megabase save when the pollution cloud seemed much bigger/denser than it was on 2.0.77. After a good bit of testing it seems that the core of the issue is that trees aren't always dying when under heavy pollution at the same rate that they used to, causing them to be harvested before they mitigated pollution by taking damage. At one point I completely disabled the clocking on a tree block to see how long it would actually take all the trees to die, and more than half of them were still alive some ~20 minutes later - and this was in a block directly under the biolabs with insane levels of pollution (20k+). In the attached image you can very clearly see when the migration to 2.1.7 happened as the mitigation amount drops sharply with nothing being changed.

pollution2.png (131.67 KiB) Viewed 524 times

There's nothing in any of the patch notes regarding trees/pollution so I'm guessing it's some ups optimization that wasn't implemented properly. Either way it's causing pollution clouds to be much larger as trees are significantly less effective at mitigating it. At this level of megabase its a huge issue.

[abucnasty]

I have experienced the same thing in my megabase after updating from 2.1.6 to 2.1.7

image.png (128.27 KiB) Viewed 494 times

[Rseding91]

It looks like this is due to the new graphics for the plantable tree. I don't *think* it's intended as the amount of pollution a tree can absorb before it's dead is not an explicit value on the tree - but part of the tree graphics definitions and seems like it was just forgotten about when making the new visuals.

[AkaraVortex]

If this is not intentional, this is pretty significant bug.

Seems new trees do not correctly react to pollution intensity, they look very similar at start of test, but it becomes more clear what's wrong later:

Natural trees taking damage:

06-26-2026, 11-31-21.png (3.41 MiB) Viewed 285 times

Planted trees taking damage:

06-26-2026, 11-32-01.png (2.69 MiB) Viewed 285 times

Not only pollution crater is not present on planted section, natural trees had absorbed much more pollution: at the edge (5 chunks) from pollution source (capable of keeping 8k pollution in one center chunk) natural trees keep ~300 pollution units, while planted have ~1500 after same amount of time.

[AkaraVortex]

Here is save file, both forests are in the corners, just place electric interface to start it:

TestTrees.zip

(2.32 MiB) Downloaded 15 times

On another look, half of planted trees are just immune to pollution, they do not get grey-Progress at all, maybe this is due to extreme (1000+) pollution in the chunk, or they are just broken.

[boskid]

Quick comparison between 2.1.6 and 2.1.7 shows decrease in amount of pollution consumed by damaged tree: 26/m in 2.1.6 but only 13/m in 2.1.7.

screen shots

06-26-2026, 09-01-21.png (2.04 MiB) Viewed 241 times

06-26-2026, 09-01-32.png (1.93 MiB) Viewed 241 times

Annoying part here is that the tree can be damaged certain amount of times (it will advance the trunk progress or grey progress), and the amount due to tree progress is directly affected by how many animation frames given TreeVariation::trunk has. So for this change to happen, what had to happen is just rework of graphics that provides different amount of trunk animation frames.

In 2.1.6, tree planted from seeds had 12 variations each with progression count of 4, while in 2.1.7 they have 8 variations each with progression count of 2. There is also an extra piece of code which says that half of trees will skip one progression step to break visual patterns, and this may be what causes some trees to not be damaged at all due to low progression count value.

[AkaraVortex]

Yeah, while new trees do look interesting, having only 2 progress stages (full leaves and no leaves, while original trees had also minor and major leaf loss) is a downgrade.
Aside from visuals, that introduces rougher curve of pollution reaction - old ones could take 1-3 stages down, each step absorbed fixed amount of pollution, new one is 0-1, but I am not certain how additional/parallel grey-Progress affects pollution.

Making extra 2 foliage would be ideal, but even without them current visual variety is decent enough, however I am not the one to judge, it would be nice to know how people rate new tree design. Quick-fix solution will be to just duplicate sprites and make 4 stages, mapping original 4 stages to 2 new ones sounds like introducing extra logic, which is suboptimal, but I am not sure how internals work here. Since tree foliage is separate layer, maybe just set lower growth progress to emulate less leaves?