SC2 Targeting AI

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On September 10 2010 06:15 broke wrote:
these units simply target randomly (the closest target) if they are left unchecked

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On September 10 2010 06:20 epik640x wrote:
Hmm, if everything just targets whatever is closest I feel better about having lings and roaches in front of Hydras.

But still the Hydras seem to go down so fast :/

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On September 10 2010 06:19 CidO wrote:
Tanks have smart AI, they do not waste shots anymore. No other unit has smart AI (Zerglings will still try to attack the thors instead of the SCVs).

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On September 10 2010 06:23 Mikami_ wrote:
My zealots always want to attack my opponents zealot/stalker instead of probes, even if they are far away..

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On September 10 2010 06:23 R0YAL wrote:
Hm thats a good question but afaik they just attack whatever has the highest priority.


They dont attack whats closest.. SC2 has a threat system so higher tier units get taken over priority over lower tier (within range).

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On September 10 2010 06:19 CidO wrote:
Tanks have smart AI, they do not waste shots anymore. No other unit has smart AI (Zerglings will still try to attack the thors instead of the SCVs).

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On September 10 2010 06:19 CidO wrote:
Tanks have smart AI, they do not waste shots anymore. No other unit has smart AI (Zerglings will still try to attack the thors instead of the SCVs).

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On September 10 2010 06:35 Lexvink wrote:


Reapers and Marines have smart AI, not sure what other units have it though.

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On September 10 2010 06:50 Piousflea wrote:
From what I understand, in SC2 most units have equal target priority. This means that units will autoattack the closest valid target. They don't make any special preference to unit type, immortals can definitely waste a lot of shots on zealots even though stalkers are within range. I am not 100% sure, but burrowed zerg units may have a lower target priority and static defenses may have a higher target priority.

So-called "smart firing" is a completely different phenomenon, and has to do with the change in unit AI.

In SC1, units do something like this:
1) (Every frame, while idle and ready to fire) Check if any valid targets are in range. If so, start attack animation.
2) (0.1sec later) Deal damage.
3) (0.3sec later) Attack animation finishes.

In SC2 it's more like this:
1) (Every frame, while idle and ready to fire) Check if any valid targets are in range. If so, start attack animation.
2) (Every frame, while attack animation is going but before damage is dealt) Check if target is dead/untargetable/invulnerable. If so, stop attack animation and return to #1.
3) (0.1sec later) Deal damage.
4) (0.3sec later) Attack animation finishes.

The SC2 attack process leads to two peculiarities:
i) All units instantly retarget when their target dies. This means that a unit with an instant attack will never waste attacks on overkill. However, units with slow projectile attacks can still overkill. (Vikings are really bad for this)
ii) It is possible for a unit to play part of its attack animation, have its target die, then immediately repeat its attack animation and hit a different target. This phenomenon is most visible on the Immortal due to its huge muzzle flash animation, and looks like the animation is stuttering.

Despite the nickname "smart firing", I think auto-retargeting is quite stupid. IMO, Blizzard should change unit AI so that it is no longer able to auto-retarget. As this would significantly change game balance (particularly nerfing siege tanks and immortals) I'm guessing it'd probably come in an expansion.

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On September 10 2010 06:39 R0YAL wrote:

Any unit without a projectile attack has "Smart AI."

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On September 10 2010 07:08 SuperGnu wrote:


THen why do immortals always without exeption(sp?) attack the non armoured units first?

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On September 10 2010 06:50 Piousflea wrote:
From what I understand, in SC2 most units have equal target priority. This means that units will autoattack the closest valid target. They don't make any special preference to unit type, immortals can definitely waste a lot of shots on zealots even though stalkers are within range. I am not 100% sure, but burrowed zerg units may have a lower target priority and static defenses may have a higher target priority.

So-called "smart firing" is a completely different phenomenon, and has to do with the change in unit AI.

In SC1, units do something like this:
1) (Every frame, while idle and ready to fire) Check if any valid targets are in range. If so, start attack animation.
2) (0.1sec later) Deal damage.
3) (0.3sec later) Attack animation finishes.

In SC2 it's more like this:
1) (Every frame, while idle and ready to fire) Check if any valid targets are in range. If so, start attack animation.
2) (Every frame, while attack animation is going but before damage is dealt) Check if target is dead/untargetable/invulnerable. If so, stop attack animation and return to #1.
3) (0.1sec later) Deal damage.
4) (0.3sec later) Attack animation finishes.

The SC2 attack process leads to two peculiarities:
i) All units instantly retarget when their target dies. This means that a unit with an instant attack will never waste attacks on overkill. However, units with slow projectile attacks can still overkill. (Vikings are really bad for this)
ii) It is possible for a unit to play part of its attack animation, have its target die, then immediately repeat its attack animation and hit a different target. This phenomenon is most visible on the Immortal due to its huge muzzle flash animation, and looks like the animation is stuttering.

Despite the nickname "smart firing", I think auto-retargeting is quite stupid. IMO, Blizzard should change unit AI so that it is no longer able to auto-retarget. As this would significantly change game balance (particularly nerfing siege tanks and immortals) I'm guessing it'd probably come in an expansion.

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