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Thor AI - inefficient unit behavior (or bug?)

Forum Index > SC2 General
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StraKo
Profile Joined February 2017
Germany96 Posts
Last Edited: 2019-10-23 17:17:05
October 23 2019 16:58 GMT
#1
Hello StarCraft friends,

I made a little video clip that shows a Thor in HIP mode fighting against a Liberator without range upgrade and a Siegetank.

I will quickly explain what you are going to see and why this AI behavior probably makes Liberators in mech vs bio a lot more powerful than intended.

First you will see the Thor outranging the Liberator on attack-move, which is intended since the Liberator lacks the range upgrade.

Then i add a Siegetank and place it directly under the Liberator.

Now when the Thor will engage, he will be attracted by the tankfire, move into the liberation circle, but then dont actually kill the Siegetank, but will instead shoot the Liberator again.

Then at last i will show that if you manually target the Liberator with the Thor, he will act normal and stay out of the Liberator circle, which results in a better trade.

https://streamable.com/mvq8h

Thor in HIP mode will generally prioritize ground units over air as far as i know.

Instead of a Siegetank, you could also use some other units to bait the Thor into Liberator range.

So technically this is working as intended and not a bug (i suppose!?).

But the problem I'm seeing is that the Thor doesn't actually proceed to kill the
static tank, but instead just moves towards him and then shoots the Liberator again.

So in order for the Thor to be a counter to unupgraded Liberators in a realistic game scenario, the Thor user has to always manually target the Liberators, because even if you micro the Thor back, he will always repeat the process of "chasing" the Tank, just to stop and then attack the Liberator again.

It's just very inefficient unit behavior and i think if the SC2 developers could find a way to improve this kind of behavior, it would help a lot to make the Thor a more responsive and "stable" unit (besides the upcoming balance changes to the Thor).

Thanks!

*Edit: I just wanted to add that this behavior probably affects a lot of other matchups and situations as well, but TvT was simply the matchup where i noticed it the most as a player, because of how common it is to face air switches in the current TvT meta.
LHK
Profile Joined May 2015
204 Posts
Last Edited: 2019-10-23 17:42:58
October 23 2019 17:23 GMT
#2
What is actually happening here is:

The Thor walks forward and has no priority to attack anything as there is nothing within its range.

The siege tank fires upon the Thor (using it's much greater range), engaging it in a type of "Responding to being attacked" logic, so it moves forward to attack the siege tank.

Once it passes into the Liberator threshold, it is attacked by the Liberator and engages in "responding to being attacked logic"

It has two potential targets to respond to- the tank, or the liberator, but Thors will always default to using their Anti-Air mode against threats when available over their ground target mode - This is a change that was made in HOTS to help Terran players deal with mass mutalisk strategies. If one were to hold position the thor outside of the liberator range, it would default to attacking the liberator, favoring it's AA attack. (Keep in mind since it hasn't been attacked by the liberator yet, but HAS been attacked by the tank, it wants to hit that tank because it fired upon the thor already - only when the liberator attacks the thor does it recognize it as a threat)

This is doubly true because the thors AA range is greater than its ground attack range, so even if the tank and liberator were equal threats, the Liberator would gain priority due to wanting to use its longer range ability, but only after it's been attacked - units don't scan terrain for threats like a lib circle, they scan for units

So, to reiterate, it is pulled into range by the siege tank attack, and then responds to the liberator attack because Thors priority is always to use its anti air against threats, so it stops not when a unit is in range, but when it is attacked by the liberator because it's engaging in "responding to being attacked" logic. (Threat goes - siege tank is a threat! lets engage!
Oh no, being attacked by liberator now, BIGGER threat, stop and attack it!)


As it is right now, there would be no way to circumvent this because by attack moving the thor, it will eat that tank shot and move to engage the tank and then be engaged by the liberator and see it as higher priority. This should only be an issue in this specific type of example though where you A-Move thors through. If the thor were A-moved and didn't eat the tank shot, it would obtain the Liberator as it's target (Example, Hellions eat the tank shots, the Thor isn't responding to being attacked, etc).. Personally I feel it's fine and is consistent logic with what we know of Thors targetting priorities and not a bug. Can see it as an annoyance though if you don't have the APM to manually correct it. Can't see this happening in other MU's as the tanks long range is what baits the thor in. Tempests, maybe, but that's about it.
-Laura
StraKo
Profile Joined February 2017
Germany96 Posts
Last Edited: 2019-10-23 17:47:17
October 23 2019 17:46 GMT
#3
Thank you for the detailed reply.

So the AI is working as intended and it is consistent with how the game logic in general works.

But i honestly still see a problem here. Let's consider that Thors are supposed to be a counter unit to Liberators, but only in the time window where the range upgrade is not researched yet and you also have to focus fire everytime you engage just to have a somewhat decent trade because otherwise they will basically suicide...

Maybe im missing a bigger picture here, but all things considered i just don't see the Thor performing as intented with the AI behaving this way and the upcoming balance changes don't change the Thor in that regard.
dragoon
Profile Joined December 2010
United States695 Posts
October 23 2019 18:18 GMT
#4
"performing as intended".....

maybe its YOU thats not performing as intended by not immediately target firing liberators with your AA thors?!!
i love you
LTCM
Profile Joined May 2017
174 Posts
October 23 2019 18:39 GMT
#5
I agree. Let's nerf tank range.
Byun is a convicted match-fixer.
LHK
Profile Joined May 2015
204 Posts
Last Edited: 2019-10-23 19:05:27
October 23 2019 18:43 GMT
#6
It has to do with unit scanning radiuses. The thor isn't scanning that far in advance for units to attack - it's only responding and reacting to the fact that it's been attacked by a siege tank, NOT it's scan radius. If you were to, for example, MOVE command the thor , and only once the liberator was in attack range issue the attack move command, it would scan, recognize the liberator as it's primary threat, and attack it. This is a niche scenario involving attack move commands and no additional player input - basically, taking the exact worst set of inputs you could possibly do and calling it a problem.

If you were to spam the attack command repeatedly as the thor is moving to engage the tank, it would acquire the liberator as its target.EDIT: This actaully isn't true and I'm going to change my stance but keep it here so I'm not being dishonest. The intended behavior SHOULD be that the thor when spammed with attack move overrides other things. Stop command doesn't work either. The thor will continue to engage the tank until it is hit by the liberator. Only Hold position works (which is not a big deal to hold position and then Attack move your units), but I actually agree with you now that this behavior is actually quite odd and not consistent with what a player would expect to happen. I tested putting the liberator slightly in front of the tank, behind the tank, etc. I couldn't get the thor to respond with repeated attack moves or stop commands, basiaclly no way to get it to attack the Lib without hold position or target firing. That said,

By doing NOTHING, you're allowing this possibility to exist, which in my mind a player would deserve - SC2 is a game that relies heavily on mechanics and understanding of the games systems, and if you completely ignore how to get around these issues, then one would in my mind deserve to lose that engagement. Hold position and then reissuing attack command is how one would overcome this issue if you did not want to manually target fire.

All of that said, this is still an issue of threat / priority. The liberator may be in range, but until it actually attacks, the threat is the siege tank. You can check this out to read a bit more about targetting: (Wiki)Automatic Targeting


-Laura
DSh1
Profile Joined April 2017
292 Posts
October 23 2019 18:49 GMT
#7
Do attack move units always prioritize units that are attacking them? I thought they always should closest unit that is not a worker?
StraKo
Profile Joined February 2017
Germany96 Posts
October 23 2019 19:32 GMT
#8
Blizzard is changing the Thors damage and attack rate values in order to improve the unit and make it more responsive but the main problem remains in my opinion.

You can fix almost every situation by just saying "git gud", but if the goal is to make Thors a better unit, i think changing the AI could be a more efficient approach than changing damage values etc.

Blizzards change does help the Thor in some cases though, don't get me wrong.

For example, Thors vs Carriers should now be easier to micro for the Terran and be less punishing. Thors prioritize Interceptors over the Carrier itself in HIP mode.

Currently the problem is that everytime the Thor is not focus firing the carrier, it will overkill on an interceptor. Combined with the slow attack rate of the Thor, this causes a huge DPS loss during battle.

So the attack rate increase is a big help.
pzlama333
Profile Joined April 2013
United States276 Posts
Last Edited: 2019-10-23 22:45:31
October 23 2019 22:27 GMT
#9
On October 24 2019 03:49 DSh1 wrote:
Do attack move units always prioritize units that are attacking them? I thought they always should closest unit that is not a worker?

(Wiki)Automatic Targeting

This liquipedia article explains well.
The automatic targeting system will choose by this order:
1. Threats. If the the opposite unit can attack you, your units will consider them as "threat". A marine will shoot a stalker over phoenix because phoenix cannot attack ground so it is not a threat for marine. A few units have "always a threat" flag.
Workers are not considered as a threat unless the owner give them attack move order.
2. Priority
Most combat units/structures have priority of 20, while a few has lower priority.
3. Multiple weapons
A few units use different weapon against ground or air units, one is primary and the other is secondary. They will use their primary weapon if there are both air and ground targets with equal threat.

4. Closest target
The closest unit is the last order automatic target system would consider, with a few exceptions


About OP question, here is the sequence:
For a Liberator hovering directly above a Siege Tank, and an opposite Thor use attack move,
If the Tank is in tank mode, the Thor will always attack the Liberator first, because Thor's AA is its primary weapon and has longer range than its anti-ground weapon. When it begins to attack the Liberator, it is still outside of Tank's attack range and does not consider it as a threat;
If the Tank is in siege mode and attack the Thor, and the Liberator is either in AA mode or siege somewhere else, the Thor will move forward to attack the Siege Tank because Tank is a threat while the Liberator is not a threat;
If the Tank is in siege mode, and the Thor moves into Liberator's defending circle, the Thor will attack Liberator first because the AA is its primary weapon.
FBTsingLoong
Profile Joined April 2018
China410 Posts
Last Edited: 2019-10-23 23:35:39
October 23 2019 23:32 GMT
#10
Thors prefers air units
TyInnoMaruByunAlive,TIMBA
TelecoM
Profile Blog Joined January 2010
United States10668 Posts
October 24 2019 03:33 GMT
#11
On October 24 2019 03:39 LTCM wrote:
I agree. Let's nerf tank range.

lol this is the best comment
AKA: TelecoM[WHITE] Protoss fighting
MockHamill
Profile Joined March 2010
Sweden1798 Posts
Last Edited: 2019-10-24 07:30:26
October 24 2019 07:27 GMT
#12
I think that no unit should target interceptors by default. Only if there is no other target presents should interceptors be attacked.

I lost count on how many viking vs carrier battles I lost because after killing a few carriers the vikings suddenly refuse to target carriers and while I frantically try to get the vikings to follow my orders half my vikings are already dead.

Having units that actively mess with the opposing players targeting causes unnecessary frustration and is bad for the game play experience. Games should be lost because the opponent played better not because your units suddenly refuse to follow your orders.

The current interceptor implementation is similar to having a special ability that turns off your opponents keyboard for 0.5 seconds. It may or may not be balanced - but is it good for the game?
Ej_
Profile Blog Joined January 2013
47656 Posts
Last Edited: 2019-10-24 07:37:34
October 24 2019 07:37 GMT
#13
On October 24 2019 16:27 MockHamill wrote:
I think that no unit should target interceptors by default. Only if there is no other target presents should interceptors be attacked.

I lost count on how many viking vs carrier battles I lost because after killing a few carriers the vikings suddenly refuse to target carriers and while I frantically try to get the vikings to follow my orders half my vikings are already dead.

Having units that actively mess with the opposing players targeting causes unnecessary frustration and is bad for the game play experience. Games should be lost because the opponent played better not because your units suddenly refuse to follow your orders.

The current interceptor implementation is similar to having a special ability that turns off your opponents keyboard for 0.5 seconds. It may or may not be balanced - but is it good for the game?

You don't want to always focus fire the carriers over the interceptors and focus firing carriers is possible, as opposed to interceptors.
Your suggestion doesn't make sense. Learn to focus fire.
"Technically the dictionary has zero authority on the meaning or words" - Rodya
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