Illusions

[fizzix]

I've been thinking about whether illusory monsters would be a useful concept. The basic idea is to create a new monster type, an illusion, that have the following characteristics:

They move exactly the same as normal monsters
They can cast spells and cause mental status effects (confusion, blindness, fear, hallucination)
They cannot cause physical status effects (all spells/attacks deal 0 damage. No stat draining, paralysis, poison, inventory destruction.)
They disappear/dissipate when you successfully attack them
They always appear to have full health, except for self-illusions.
They are always awake, except for static illusions which can never awaken.
They cannot cause any physical damage (all attacks and spells deal 0 damage)
They can be dissipated by stronger monsters that push past them (but weaker monsters are afraid to try.)

Then we could have the following monster spells:

SUMMON_ILLUSIONS: summons monsters as our normal summon_monster spell, perhaps with a small (5%) chance of an illusion being a real monster.
similarly there could be spells like,
SUMMON_IDRAGONS: summons illusory dragons. etc. etc.
CLONE_SELF: Make several illusory copies of the monster casting the spell. These illusions appear to have the same HP as the casting monster at all times. Upon casting, the caster immediately swaps places with one of the illusions.

Also the player spell
DISPEL_ILLUSIONS: Remove all illusions in line of sight.

You could have static illusions that appear on trap squares (when the player tries to attack, they step on the trap.)

There could also be a intermediate step between, full realistic illusion and dissipated. This would be an illusion that exists but that is recognized by @ as faulty. This illusion continues to act as normal but can no longer cause status effects. It would be nice to distinguish a known fake from the real deal to the player. If @ knows the player should be able to see this as well.

I'm guessing area of effect spells should dissipate all illusions, but this seems a little cheap. Maybe there's another approach?

Here are some basic monsters that I think should have the spells.

Illusionist, mage: S_Illusion
Sorcerer, Dark elven sorcerer: S_illusion, clone self
Will of the wisp, harowen, draebor: clone self


Lastly, there is probably a way to also allow @ to create self-illusions, but this doesn't seem useful enough to be worth the tremendous hassle involved.

[will_asher]

I've been thinking about whether illusory monsters would be a useful concept. The basic idea is to create a new monster type, an illusion, that have the following characteristics:

I have illusory monsters in DaJAngband. Currently they only appear when hallucenating (instead of the old hallucenation effect), but I like these ideas.

They move exactly the same as normal monsters
They can cast spells and cause mental status effects (confusion, blindness, fear, hallucination)
They cannot cause physical status effects (all spells/attacks deal 0 damage. No stat draining, paralysis, poison, inventory destruction.)
They disappear/dissipate when you successfully attack them
They always appear to have full health, except for self-illusions.
They are always awake, except for static illusions which can never awaken.
They cannot cause any physical damage (all attacks and spells deal 0 damage)
They can be dissipated by stronger monsters that push past them (but weaker monsters are afraid to try.):

In DAJ, timed effects (like confusion) caused by illusions are much shorter-lasting, and they can't inflict those physical status effects like you said. Also, they don't do any actual damage and they are always awake.
Unlike how you describe them, illusions in DAJ lose hit points as normal. They start with a fraction of the hit points that that race of monster normally has, and they dissapate when they hit 0 HP (no XP or drops obviously).

Then we could have the following monster spells:

SUMMON_ILLUSIONS: summons monsters as our normal summon_monster spell, perhaps with a small (5%) chance of an illusion being a real monster.
similarly there could be spells like,
SUMMON_IDRAGONS: summons illusory dragons. etc. etc.
CLONE_SELF: Make several illusory copies of the monster casting the spell. These illusions appear to have the same HP as the casting monster at all times. Upon casting, the caster immediately swaps places with one of the illusions.

Also the player spell
DISPEL_ILLUSIONS: Remove all illusions in line of sight.

Thanks to this post, I will probably be adding these monster spells very soon (except I won't bother with the specific racial summoning illusion spells -no SUMMON_IDRAGONS). The applicable PC spell is true seeing, which is already in the game. (True seeing in DAJ does more than just make you see invisible. You also recognise mimics automatically and have higher alertness).

There could also be a intermediate step between, full realistic illusion and dissipated. This would be an illusion that exists but that is recognized by @ as faulty. This illusion continues to act as normal but can no longer cause status effects. It would be nice to distinguish a known fake from the real deal to the player. If @ knows the player should be able to see this as well.

This is also something I will likely add soon.

Lastly, there is probably a way to also allow @ to create self-illusions, but this doesn't seem useful enough to be worth the tremendous hassle involved.

I decided not to bother with PC invisibility spell for a very similar reason. I'd have to keep track of which monsters use scent to locate the PC as well as which ones can see invisible, and make a system for how well monsters can figure out where you are by your noise, etc.

[Magnate]

I decided not to bother with PC invisibility spell for a very similar reason. I'd have to keep track of which monsters use scent to locate the PC as well as which ones can see invisible, and make a system for how well monsters can figure out where you are by your noise, etc.

But it would be excellent to have such a system. Any decent 5GAI ought to have this anyway, thereby facilitating invisibility and a whole host of other cool stuff. Presumably fizzix's "self-illusion" is what's normally called a Mirror Image spell?

[Derakon]

Not having played DaJ, what are the impacts on gameplay of having illusory monsters? How do we handle monster memory for the spells -- when does the player learn that the summons were illusory? What if we have a monster that can summon both illusory and real versions of the same monster type? If the player learns they're illusions on seeing the spell cast for the first time, then on subsequent castings they "ought" to be able to tell if the summons are illusions or not, but cannot because the monster memory has already been filled in.

Don't mind me, I'm just being difficult.

[Mikko Lehtinen]

I decided not to bother with PC invisibility spell for a very similar reason. I'd have to keep track of which monsters use scent to locate the PC as well as which ones can see invisible, and make a system for how well monsters can figure out where you are by your noise, etc.

Ey and Fay have player invisibility.

Each turn, there's a random check depending on Stealth skill that a monster knows where you are. The same mechanic is used for blinded monsters.

Some monsters have SEE_INVISIBLE flag.

[buzzkill]

Invisibility implies more than just "hard to see". Invisibility shouldn't be dependent on stealth (IMO). Scent based location seems more "real". It would be great in DAJ could nail this down. It's really a better variant (of V) than it gets credit for.

[fizzix]

Not having played DaJ, what are the impacts on gameplay of having illusory monsters? How do we handle monster memory for the spells -- when does the player learn that the summons were illusory? What if we have a monster that can summon both illusory and real versions of the same monster type? If the player learns they're illusions on seeing the spell cast for the first time, then on subsequent castings they "ought" to be able to tell if the summons are illusions or not, but cannot because the monster memory has already been filled in.

Don't mind me, I'm just being difficult.

I think illusion summons should be obvious to the player, but not necessarily to @. However, I like the idea that even with illusion summons there's a small chance that the monster is real. This keeps the player honest. This way summoned illusions can always be considered as real monsters, even though there's something like a 95% chance that they're not.

@will_asher: when did you add illusions? I don't remember them the last time I played DJA.

[Derakon]

This way summoned illusions can always be considered as real monsters, even though there's something like a 95% chance that they're not.

So the message would be "The Sorceress summons illusory dragons!" and the monster memory would say "she can cast spells that summon illusory dragons" but the spell would sometimes pull in a real one?

I dunno, I think that crosses the line into outright lying to the player.

[will_asher]

I think illusion summons should be obvious to the player, but not necessarily to @. However, I like the idea that even with illusion summons there's a small chance that the monster is real. This keeps the player honest. This way summoned illusions can always be considered as real monsters, even though there's something like a 95% chance that they're not.

@will_asher: when did you add illusions? I don't remember them the last time I played DJA.

I think 1.3.0 was the first version that had illusion monsters appear when hallucenating.

I think with a summon illusion spell, it should not initially be obvious to either the player or the PC. When the spell is cast, it should be the usual message for S_MONSTER or S_MONSTERS. When the PC dispels one of the illusory monsters, then he learns that the monster has the summon illusion spell for monster memory.
If the monster has both S_MONSTERS and S_ILLUSIONS, neither the PC nor the player should be able to tell which one is being cast (even if he has full monster memory) until the first illusion is dipelled (or recognised as an illusion some other way).
The problem with this is I wouldn't know what to do with monster memory between the casting of the spell and the dispelling of the first illusion.

I don't think a summon illusion spell should ever summon real monsters, but maybe there'd be a chance of a semi-real illusory monster, which would allow the illusion to do some damage (though probably still just a fraction of the real monster's damage) and have slightly more effective spells than other illusions.
(D&D has shadow illusion spells which can do damage and have effects as if the illusion was semi-real.)

[Mikko Lehtinen]

Invisibility implies more than just "hard to see". Invisibility shouldn't be dependent on stealth (IMO). Scent based location seems more "real". It would be great in DAJ could nail this down. It's really a better variant (of V) than it gets credit for.

I think it should be both scent and noise.

In Fay the flavour of Invisibility is "impossible to see". But since Stealth governs moving silently, IMO it's natural that it helps.

Fay doesn't have sophisticated noise mechanisms. I think Sangband does, for example.

I'm very interested in DaJ. I just skimmed through the dungeon generation for ideas. I'll probably borrow "interesting rooms" at some point.

[Scatha]

In Fay the flavour of Invisibility is "impossible to see". But since Stealth governs moving silently, IMO it's natural that it helps.

Sil works similarly. Indeed Stealth is perhaps primarily about noise, and uses a 'sound distance' in calculations (there are also separate noise-creating events), but it's abstracted away enough that we're happy giving visual clues as a bonus to the roll to notice. Player invisibility isn't currently in the game, but it might go in at some point, and has a natural mechanical interpretation: completely removing this visual bonus (compared to disguise, which halves it).

[fizzix]

I've thought quite a bit about player invisibility also, and I've had some questions about how it's implemented in variants that use it.

1) What levels of awareness do monsters have? I can think of the following. a) asleep. b) awake but unaware of @'s existence. c) awake, aware of @'s existence, but not where @ currently is on the level. d) awake, aware of @ being nearby, but not exact location. e) awake, knowledgeable of @'s current location. Maybe there are others too?

2) Is invisibility binary, or can it have an associated skill level? If binary, do certain monsters have the see invisible skill? If not, do monsters use a separate statistic beside the awareness stat?

3) Will monsters attack an invisible monster if they can't see it? For example, an orc without the ability to see invisible wants to get to @ but there's a poltergeist in the square between. The orc shouldn't know of the ghost's existence, so it should try to move into that square, at which point it should attack the square. If this isn't the case, would it change if @ was invisible too and the orc tried to move into a square with an invisible monster?

4) Do monsters have the telepathy skill in the same way that @ does? In which case, invisibility is obsolete when telepathic monsters start showing up.

[Magnate]

I've thought quite a bit about player invisibility also, and I've had some questions about how it's implemented in variants that use it.

1) What levels of awareness do monsters have? I can think of the following. a) asleep. b) awake but unaware of @'s existence. c) awake, aware of @'s existence, but not where @ currently is on the level. d) awake, aware of @ being nearby, but not exact location. e) awake, knowledgeable of @'s current location. Maybe there are others too?

This seems like a comprehensive hierarchy to me, though I don't know if it's implemented anywhere.

2) Is invisibility binary, or can it have an associated skill level? If binary, do certain monsters have the see invisible skill? If not, do monsters use a separate statistic beside the awareness stat?

In Sangband, which is the only variant I've played with player invisibility, it's a pval-set ability (like light radius). So items can increase your invisibility rating. I don't know how it's checked (but it would be easy to look up).

3) Will monsters attack an invisible monster if they can't see it? For example, an orc without the ability to see invisible wants to get to @ but there's a poltergeist in the square between. The orc shouldn't know of the ghost's existence, so it should try to move into that square, at which point it should attack the square. If this isn't the case, would it change if @ was invisible too and the orc tried to move into a square with an invisible monster?

I think it's a pretty strong rule in most *bands that monsters don't attack each other. But I think a trampler should trample over a monster it can't see if it wants to move into that square.

4) Do monsters have the telepathy skill in the same way that @ does? In which case, invisibility is obsolete when telepathic monsters start showing up.

Well of course at the moment ALL monsters in V/v4 have telepathy, because they always know where @ is when they're awake. But giving this ability to a small number of monsters, once your original hierarchy of awareness is implemented, would be cool IMO.

[Mikko Lehtinen]

I forgot to mention that in Ey and Fay invisibility goes off for a turn when you attack. I guess that's because of D&D influence.

[Derakon]

Does that apply to when ghosts attack the player, too? There'd be a lot less random flailing in the game if the player could see ghosts after they attack him.