Factorio Forums

I have some issues with how biters behave in the game, by far the most annoying one is biters trying to attack the player while he's moving by train. You can leave kilometers of undefended railway for hours and biters will never go after the passing trains, but should the player travel there then is like you hit every hornet nest along the way and you end up with aliens all over the tracks, all inactive and never going away until they are run over by the next train. If a behemoth is hit it'll wreck the locomotive, and the alien mob will still remain frozen until the player gets there and manually clears the tracks.

I have read threads of players complaining about behemoths being capable tanking the hit of a train and destroying it, but I have no problem with that, my issue is how we get into that situation: if the player never visits an outpost nothing ever happens, if the player visit an outpost then trains end up running over braindead behemoths. It would be a different situation If the biters were crossing the tracks when hit (as it can happen when they attack the factory).

What ?

Change the aggro conditions so the alien fauna won't try to attack the player if he's moving by train at a speed faster than themselves, unless attacked.

Why ?

I know that deploying artillery and actively protecting railways or walling off makes this a non-issue, but still I think this change should be made, because:

• The game's simulation has clearly shown me that actively defending rail tracks isn't necessary, despite what the wiki says trains are not a priority target and biters never engage them unless run over first. Is not until the player travels near them by train that it triggers all the aliens along the railway.
• It discourages the player from visiting outposts. I have avoided visiting outposts because I would need to travel back by foot, mopping up all the biters that remained frozen in the tracks.
• It makes no sense lore-wise. Why do biters attack the train the player is in but ignore the trains the player is not?, what difference does it makes if the player is in the train or not? To the alien fauna it should be the same thing, it should either attack all trains or none.
• It really highlights the bad aspects of the game simulation and the measures it has to make for save UPS, because biters are inactive and frozen in place unless is in a chunk with pollution or the player is near. This means that after chasing a train biters will deactivate while over the tracks, and will stay there, frozen, never returning to the nest they are supposed to protect, until hit by a train or activated by something else. If we can't improve the simulation of biters then at least we could try to hide the inconsistencies.

I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

I fully agree with this.

However, I'm afraid that it would be bad for performance if there were constantly hundreds of biters chasing trains on the map, since the biters would have to constantly pathfind instead of simply sitting around.

Well, in my experience, that's already what happens :
Player takes the train
=> Biters chase the train and stop on the track
=> Next train without player kills a biter on the tracks
=> Biters chase the train and stop on the track
=> Repeat ad infinitum, no player in train needed

(Shouldn't the biters instead "go home" after a while?)

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

That's the alternative, but unless Wube makes some breakthrough with the biter AI or decides that is ok to sacrifice UPS for more biter activity I don't think It can happen, so I didn't suggest it.

Tekky wrote:

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

I fully agree with this.

However, I'm afraid that it would be bad for performance if there were constantly hundreds of biters chasing trains on the map, since the biters would have to constantly pathfind instead of simply sitting around.

Not quite path finding as they wouldn't chase trains. They would be following pollution. But yeah, more aliens moving around == more cpu time.

m44v wrote:

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

That's the alternative, but unless Wube makes some breakthrough with the biter AI or decides that is ok to sacrifice UPS for more biter activity I don't think It can happen, so I didn't suggest it.

In each chunk there should be a vector pointing in the direction of pollution. The pollution spreading algorithm can update that vector and by considering the amount of pollution spread you get more than just the cardinal directions. Aliens with no goal but within pollution could then just wander in roughly the direction pointed by that vector. A directed random walk. This should avoid costly path findings.

mrvn wrote:

m44v wrote:

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

That's the alternative, but unless Wube makes some breakthrough with the biter AI or decides that is ok to sacrifice UPS for more biter activity I don't think It can happen, so I didn't suggest it.

In each chunk there should be a vector pointing in the direction of pollution. The pollution spreading algorithm can update that vector and by considering the amount of pollution spread you get more than just the cardinal directions. Aliens with no goal but within pollution could then just wander in roughly the direction pointed by that vector. A directed random walk. This should avoid costly path findings.

Yeah, that's an idea I've had before as well. The biter AI could be significantly simplified if pathing was largely just "go to the adjacent chunk with the most pollution, and then if there are things there, attack them."

Jap2.0 wrote:

mrvn wrote:

m44v wrote:

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

That's the alternative, but unless Wube makes some breakthrough with the biter AI or decides that is ok to sacrifice UPS for more biter activity I don't think It can happen, so I didn't suggest it.

In each chunk there should be a vector pointing in the direction of pollution. The pollution spreading algorithm can update that vector and by considering the amount of pollution spread you get more than just the cardinal directions. Aliens with no goal but within pollution could then just wander in roughly the direction pointed by that vector. A directed random walk. This should avoid costly path findings.

Yeah, that's an idea I've had before as well. The biter AI could be significantly simplified if pathing was largely just "go to the adjacent chunk with the most pollution, and then if there are things there, attack them."

"go to the adjacent chunk" would be a path finding to the center of the chunk or so. I don't think that would behave natural. You only have 8 directions the alien can go that way. And what if that center tile is water?

My idea with the vector would allow more directions. If 66% pollution come from the north and 33% from the west then you would get a vector that points NNW. So the aliens would wander around moving mostly in that direction but also a bit off vector as well. So even if they start from the same spawner each will go a slightly different way. Some might get trapped in dead ends. Some go left around a cliff and some right. Eventually one will find your base, attack. This should draw in all near aliens with direct path finding I think.

Scouts would be cool to. Have the alien walk till it finds the base and then return to the spawner to tell everyone else about it. Bring back info about what happened to previous aliens so the next attack will use a larger group.

mrvn wrote:

Jap2.0 wrote:

mrvn wrote:

m44v wrote:

mrvn wrote:I would go the other way and say aliens should be aggravated by trains. Why?

Trains burn fuel and that should produce pollution. So as they drive along a track they should spread pollution. When the pollution hits any aliens they should follow the stink and wander along (and across) the train track trying to find the source of the stink. Would be more realistic.

That's the alternative, but unless Wube makes some breakthrough with the biter AI or decides that is ok to sacrifice UPS for more biter activity I don't think It can happen, so I didn't suggest it.

In each chunk there should be a vector pointing in the direction of pollution. The pollution spreading algorithm can update that vector and by considering the amount of pollution spread you get more than just the cardinal directions. Aliens with no goal but within pollution could then just wander in roughly the direction pointed by that vector. A directed random walk. This should avoid costly path findings.

Yeah, that's an idea I've had before as well. The biter AI could be significantly simplified if pathing was largely just "go to the adjacent chunk with the most pollution, and then if there are things there, attack them."

"go to the adjacent chunk" would be a path finding to the center of the chunk or so. I don't think that would behave natural. You only have 8 directions the alien can go that way. And what if that center tile is water?

My idea with the vector would allow more directions. If 66% pollution come from the north and 33% from the west then you would get a vector that points NNW. So the aliens would wander around moving mostly in that direction but also a bit off vector as well. So even if they start from the same spawner each will go a slightly different way. Some might get trapped in dead ends. Some go left around a cliff and some right. Eventually one will find your base, attack. This should draw in all near aliens with direct path finding I think.

Scouts would be cool to. Have the alien walk till it finds the base and then return to the spawner to tell everyone else about it. Bring back info about what happened to previous aliens so the next attack will use a larger group.

Yeah, that's probably a better idea. I wasn't strictly thinking go to the center, more just in that general direction, but I suppose there's no reason to go only in the cardinal (and maybe intermediate) directions. Scouts would also be cool, whether it be a new unit with faster speed or simply a biter/spitter with different AI.