[Bug] Stealth detection spells without provocation

Cadros · June 2012

Game Behaviour at Present

If my character sneaks up on certain enemies while invisible, as soon as my character is in range they start to cast a spell to remove invisibility.

Expected Behaviour

Most enemies would be very unlikely to be able to spot that someone invisible was approaching, and therefore I would expect that most of the time if the enemy has not yet engaged with you at any point then they would not cast invisibility removal spells.

AlexT · June 2012

This is a deliberate design decision made by the original developers and not a bug. Certain characters (i.e. Perth the Adept in BG2) have been specifically scripted to exhibit this behavior. Here's an excerpt from MAGE18B.BCS:

IF
  Allegiance(Myself,ENEMY)
  Detect([PC])
  !See(LastSeenBy(Myself))
  HaveSpell(WIZARD_TRUE_SIGHT)
THEN
  RESPONSE #100
    Spell(Myself,WIZARD_TRUE_SIGHT)
END

In theory, an opponent could still hear the footsteps of your invisible character and react based on that. Ideally, there should be a Move Silently check in there to account for truly stealthy characters, but that's more along the lines of a feature request.

Cadros · June 2012

I bow to your superior knowledge, and would be happy to settle for a move silently/ dexterity based check

technophobe · June 2012

That happens even when it's a stealthed thief who likely won't be heard, either. Just another example of bad/lazy AI.

AlexT · June 2012

That happens even when it's a stealthed thief who likely won't be heard, either. Just another example of bad/lazy AI.

That could be avoided with relative ease by changing the aforementioned block to something like this:

IF
  Allegiance(Myself,ENEMY)
  Detect([PC])
  !See(LastSeenBy(Myself))
  CheckStatLT(LastSeenBy(Myself),40,STEALTH) // Move Silently is less than 40
  !StateCheck(LastSeenBy(Myself),STATE_SILENCED) // not under a Silence spell
  HaveSpell(WIZARD_TRUE_SIGHT)
THEN
  RESPONSE #100
    Spell(Myself,WIZARD_TRUE_SIGHT)
END

Using the revised block, the opponent could not detect an invisible character with a Move Silently score of 40+ nor could he hear an invisible character affected by a Silence spell. I use similar script blocks for certain opponents in my mods.

Boaster · June 2012

Yes, this is something that is ludicrous. The AI check should be more involved. Cuz you just can't sneak past a beholder.

Like, every 6 seconds there should be a check. If an invisible target is moving, do a check against stealth, move silently, dexterity and so forth. Avenger's script looks good.

Lunever · June 2012

There is a bug though - a ranger's STEALTH is internally written in the character's Move Silently AND Hide in Shadows skill value (which is correct).
However, the original devs forgot to change the skills of a Thief ALSO to Stealth, a Thief only has Move Silently and an internal Hide in Shadows Skill of 0. I fixed that with Shadowkeeper after every thief level-up as a workaround so far and set HiS = MS.

[Bug] Stealth detection spells without provocation

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