Seeing Through Your Own Illusions?

[DrowPiratRobrts]

Can casters see through there own illusions? Are there RAW for this? If not, it seems silly to me that a caster who creates an illusion wouldn't be able to see through it as if he or she had rolled an intelligence check. From now on I think I'm going to allow this in my own games unless any of you know of rules that seem to dictate this shouldn't be allowed.

PC: I cast Major Image to create the illusion of a wall between me and the enemy.
DM: Okay, you do that.
PC: Now what do I see the enemy doing?
DM: Um...you created a wall. You can't see through it.
PC: But I know it's an illusion...I made it myself.
DM: Make an intelligence check to overcome the illusion in your own mind.
PC: But I know it's an illusion...
DM: Yeah, well WotC is really confusing sometimes and I don't know if they ever wrote a rule about this...
PC: Let's go to the playground to find out!
DM: Yes, they can save us from our inner turmoil precious. *gollum* *gollum*

[leogobsin]

I'm fairly certain just about every illusion spell specifies that physical interaction proves it to be an illusion (Major Image, the one you specified definitely does), so even if you couldn't automatically see through it just poke your finger into the wall and you definitely can see through it.

[Resileaf]

I've always been under the impression that creating an image illusion created a fully opaque thing that you couldn't see through and that even if you don't believe there's really a wall there, you still see the image because it doesn't stop existing. Have I been assuming wrong the whole time?

[leogobsin]

I've always been under the impression that creating an image illusion created a fully opaque thing that you couldn't see through and that even if you don't believe there's really a wall there, you still see the image because it doesn't stop existing. Have I been assuming wrong the whole time?

I think so, yeah. From the description of Silent Image: "If a creature discerns the illusion for what it is, the creature can see through the image." Minor Illusion and Major Image have similar sentences in their descriptions. The intent is, if you physically interact with an illusion or use an action to make an Intelligence (Investigation) check vs. the caster's spell save DC, the illusion is still there but is translucent and any non-visual elements become very faint.

[Willie the Duck]

Can casters see through there own illusions? Are there RAW for this?
I am AFB right now, so will let others answer this.


If not, it seems silly to me that a caster who creates an illusion wouldn't be able to see through it as if he or she had rolled an intelligence check.

I think, if I were not steeped in D&D-isms from 35 years of gaming, I think I would think the expectation that one could see through illusions at all, simply because you had sussed-out that they were illusions, to be utterly foreign and bizarre. I mean, let's take your example of an illusionary wall. Why should disbelieving the illusion allow one to see through it? The magic either put the image of the wall into the minds of all viewers of that area, or placed a point of light emission showing a wall in that specific place. Recognizing that the wall isn't there shouldn't naturally allow one to somehow see what is actually there for any specific reason.


I think so, yeah. From the description of Silent Image: "If a creature discerns the illusion for what it is, the creature can see through the image." Minor Illusion and Major Image have similar sentences in their descriptions. The intent is, if you physically interact with an illusion or use an action to make an Intelligence (Investigation) check vs. the caster's spell save DC, the illusion is still there but is translucent and any non-visual elements become very faint.

Yes, that seems to be the intent. However, I have never figured out exactly why that was chosen to be the case.

[Kadesh]

I've always assumed 'see through' was just the knowledge that it was an illusion, rather than being able to ignore the illusion as if it were not present.

Making an illusion of a Rock still makes a rock, but you have seen through the fact its an illusion, but you still can't ignore the Line of Sight blocking properties of the illusory rock.

[PhantomSoul]

I've always assumed 'see through' was just the knowledge that it was an illusion, rather than being able to ignore the illusion as if it were not present.

I'd been imagining it as a third option: partial transparency / translucence. That was based on generalising lines like


A creature who discerns the illusion for what it is, sees it as a vague image superimposed on the terrain.

from Hallucinatory Terrain and


the creature can see through the image, and its other sensory qualities become faint to the creature

from Major Image (where the image is seen-through but not absent, just like the other sensory qualities become faint rather than absent). There are some other phrasings for non-visual elements like "any noise it makes sounds hollow to the creature" in Programmed Illusion and in Project Image. Minor Illusion even phrases the visual element as


the illusion becomes faint to the creature.

But generalising that to be assumed for all illusions might not be RAW (consistent with the cases I checked, but I didn't do a comprehensive search). It does help with Truesight-havers being aware of the presence of Mirage Arcane

[DrowPiratRobrts]

I think, if I were not steeped in D&D-isms from 35 years of gaming, I think I would think the expectation that one could see through illusions at all, simply because you had sussed-out that they were illusions, to be utterly foreign and bizarre. I mean, let's take your example of an illusionary wall. Why should disbelieving the illusion allow one to see through it? The magic either put the image of the wall into the minds of all viewers of that area, or placed a point of light emission showing a wall in that specific place. Recognizing that the wall isn't there shouldn't naturally allow one to somehow see what is actually there for any specific reason.



I actually agree that it never made a ton of sense to me that the illusion becomes faint but remains. In my mind, if you did succeed in determining that something is an illusion it should either remain but you know it's fake or it should go completely from your mind.

But that's not the way they wrote these spells, so I'm thinking that I should just allow casters to see through their own illusions if there's no rule one way or the other. I just can't get around the fact that an enemy has a chance to role and see through the illusion, but the caster himself does not. As stated above, you could interact physically with it, but that's only if you're right next to it so this becomes an issue for most illusions that casters throw out.

[DrowPiratRobrts]

I found this argument really compelling on another thread/website:

No, it does not affect the caster
The reason is quite simple, as stated in the rules:

If a creature discerns the illusion for what it is, the illusion becomes faint to the creature.

The key part for the caster is highlighted. Without a single shred of doubt, the caster knows what it is, therefore the caster is not affected.

Another proof, a longer one, would be looking on how some illusions, in particular this illusion, are found out. An extract from Silent Image:

Physical interaction with the image reveals it to be an illusion, because things can pass through it.

And from Disguise Self

The changes wrought by this spell fail to hold up to physical inspection.

The way illusions are found out is by investigation. And that talks about the thought process that it is needed to reach the conclusion that the illusion is, in fact, an illusion. The affected creature needs a reason to believe that what he is seeing is an illusion, the caster does not:

A strange statue in an art museum would not trigger the need to investigate but same statue in your room, where it was not before, is a reason to investigate. The narrative in some cases is "the hand passes through the object", but it can also be "Bob, with his innate talent to bypass the most mundane situation, was exceptionally sharp this time. He discover the shimmer that the wizard always forget to take out".

Everything in the arsenal of the illusions point out the need for an ignorant target. A target that can't discern, figure it out, knows, that the presented phenomena is an illusion. You are not ignorant on your own doings, at least not in this case. It is a direct consequence of your actions and, therefore, your illusions do not affect you. Sadly for your comrades they always doubt, cursing you for being better and better at it as you gain experience.

[Tanarii]

I'm fairly certain just about every illusion spell specifies that physical interaction proves it to be an illusion (Major Image, the one you specified definitely does), so even if you couldn't automatically see through it just poke your finger into the wall and you definitely can see through it.
Its debatable / interpreation as to if the physical interaction and investigation check/see through clauses are seperate or not.

[Battlebooze]

Hah, this has been debated before and the idea that the caster can't automatically see through his illusions leads to all sorts of stupid madness.

Illusionist Player: "I create an illusion of a wall of stone in front of the party! That way we can hide behind it when the orcs come."
GM: "Ok, a stone wall appears. I assume everyone hides behind it and stays quiet?"
Party: "Yes, we hide behind the illusion."
Illusionist Player: "When the orcs move past us, I will stop concentrating and we will ambush the orcs. They won't see us coming!"
GM: "You can't see the orcs to know that, there is a stone wall in front of you."
Illusionist Player: "What? You mean behind the one I created?"
GM: "You can't tell, but there seems to be a stone wall right in front of you. It seems real to you."
Illusionist Player: "Oh, where did that come from? Okay, I stop concentrating on my spell then, since there seems to be a wall already there."

GM: The Orcs stare at the party, pulling their weapons as the Illusion fades away. Roll initiative.

Illusionist player: /facepalm

[Louro]

Hah, this has been debated before and the idea that the caster can't automatically see through his illusions leads to all sorts of stupid madness.

Illusionist Player: "I create an illusion of a wall of stone in front of the party! That way we can hide behind it when the orcs come."
GM: "Ok, a stone wall appears. I assume everyone hides behind it and stays quiet?"
Party: "Yes, we hide behind the illusion."
Illusionist Player: "When the orcs move past us, I will stop concentrating and we will ambush the orcs. They won't see us coming!"
GM: "You can't see the orcs to know that, there is a stone wall in front of you."
Illusionist Player: "What? You mean behind the one I created?"
GM: "You can't tell, but there seems to be a stone wall right in front of you. It seems real to you."
Illusionist Player: "Oh, where did that come from? Okay, I stop concentrating on my spell then, since there seems to be a wall already there."

GM: The Orcs stare at the party, pulling their weapons as the Illusion fades away. Roll initiative.

Illusionist player: /facepalm
Oh sir, I do feel quite identified with that illusionist player :(

[Vekon]

The idea that an Illusionist wouldn't be able to see through his own illusory affects is absurd. You created it, you know it is an illusion. A DM arguing that your party cannot see through it is one thing, but the caster themselves should be able to 100% of the time.

[bc56]

Of course.

That's what Roy's Archon ruled, and could an incarnation of Law and Good be wrong about this? It makes the most sense and is the kindest interpretation to the player.

Here's the relevant OOTS #565 (http://www.giantitp.com/comics/oots0565.html)

[Lunali]

I think, if I were not steeped in D&D-isms from 35 years of gaming, I think I would think the expectation that one could see through illusions at all, simply because you had sussed-out that they were illusions, to be utterly foreign and bizarre. I mean, let's take your example of an illusionary wall. Why should disbelieving the illusion allow one to see through it? The magic either put the image of the wall into the minds of all viewers of that area, or placed a point of light emission showing a wall in that specific place. Recognizing that the wall isn't there shouldn't naturally allow one to somehow see what is actually there for any specific reason.

My interpretation is that it is the former, that the illusion is put into the minds of all viewers. Knowing that it is an illusion allows your mind to recognize the real information gathered by your senses instead of the false information provided by the spell.

[Louro]

I think phantasmal force is actually put onto your mind, but minor image and the like are "real" illusions. Invisibility and mirror image are also real illusions.

[Kadesh]

The idea that an Illusionist wouldn't be able to see through his own illusory affects is absurd. You created it, you know it is an illusion. A DM arguing that your party cannot see through it is one thing, but the caster themselves should be able to 100% of the time.

I can see through the magic trick to seperate my thumb from my hand, but I still see its effects.

[Segev]

First off, it's magic: if it "doesn't make sense" that you can still see it as a translucent overlay/vague outline/whatever, but couldn't see through it before, despite it really being there, tough. It's magic, and somehow it does that.

That said, let's look at the rules we have.

1) The image is revealed to be false if somebody succeeds on an Investigation check against the relevant Spell DC.
2) The image is revealed to be false by "physical interaction."
3) Those who see the image as false can see through it, but can still also see a vague outline of it.

Starting with (3), what I read this as saying is that, no, a discerned illusion can't be used to block sight, but yes, those who've determined correctly that it is illusory are still aware of what the illusion looks like and is doing.

Item (2) is the stickiest of these. What, precisely, is "physical interaction?" You will find people arguing that it is anything "going through" the image, no matter how reasonable that looks nor whether it would happen if the illusion were a real example of the phenomenon. You will find people arguing that the Investigation roll requires touching it to see through it, and can't be done from a distance.

I think neither of these is really in line with the way the spell effects are written.

If you break down what these are trying to say, it seems to me that they're telling us that knowing for sure that the illusion is illusory means you can see through it, as described in (3). Items (1) and (2) are giving methods of gaining that knowledge. If "things going through it" wouldn't really give away its illusory nature (e.g. a bank of fog or "magical darkness" or the like), then it is insufficient physical interaction by itself for (2) to auto-trigger. (2) is really just an effort to allow for detection when there's no way the illusion COULD fool somebody anymore.

(1) is the primary mechanism. The successful Investigation check notices and recognizes some discrepancies that reveal the illusion's false nature. (2), again, is just a special case that reduces (1)'d DC to (automatic). It is not a blanket "illusions fail because air goes through them" thing.

Therefore, I think it important to keep in mind that what (1) and (2) are really getting at is that the thing that makes an illusion fail for a particular observer is the observer knowing for a fact that it is not real. If we use that understanding, coherent adherence to (1) and (2) naturally follows, and we have a much easier time ruling corner cases.

What does this mean for illusionists and their own illusions? The DM may be in his rights to demand that Investigation check, but honestly, the illusionist HAS to know. His allies...may or may not. Sure, if he alerts them, they "know," but they might find it so convincing that they can't believe it until they convince themselves by some manner of proof. The DM, I think, is reasonable to either let them automatically see through it, or to force them to roll Investigation. But if the latter, he really should give them Advantage: they know, intellectually, it's not real, so will have an easier time spotting that evidence that lets them lock it down in their minds.

[Louro]

I think the idea is pretty close to this:

- Illusions are real, they are really there. You can even make them feel real (heat, sounds, movement...)
- Once disbelieved you see the reality, but can still also see the illusion as a superimposed semi-transparent thing.
- They are meant to create objects, creating fog goes a bit beyond fair use. (Unless noted otherwise)
- Save to disbelieve is actually an investigation check. (requires action)
- If illusion is inconsistent* or compromised by enviromet then a Perception check might reveal it (no action required).
- Proof* will inmediatly reveal it to inteligent creatures.

*Inconsistency: snow going through the illusion (perception to notice). At this point you can either reveal the illusion (if obvious) or let the players investigate it.
A dancing bear wearing a tu-tu could be inconsistent also, depending on the setting.
*Proof: "Hey folks look! Somehow I am inmune to fire now!"

An illusionary wall on a corridor might look suspicious or extrange, granting the players reasons enough to investigate it.
An illusionary wall hidding a corridor on a 4-way intersection (turning a 4-way into a 3-way) won't give any clue to justify an investigation check. If they search for traps I roll the investigation behind the screen. If they look for hidden doors they will find the illusion automatically.

[Segev]

- They are meant to create objects, creating fog goes a bit beyond fair use. (Unless noted otherwise)

Point of order: only minor illusion specifies that it creates objects only. (Well, and creation, but that's a very different spell than the ones we're discussing.) Silent image can explicitly create creatures and "phenomena," as can the spells that are more-or-less higher-level versions of it (major image, programmed image, etc.). Fog is absolutely valid as a "phenomenon."

[Louro]

Point of order: only minor illusion specifies that it creates objects only. (Well, and creation, but that's a very different spell than the ones we're discussing.) Silent image can explicitly create creatures and "phenomena," as can the spells that are more-or-less higher-level versions of it (major image, programmed image, etc.). Fog is absolutely valid as a "phenomenon."
Wait a second... you can create smoke or fog, and move with it. Invisibility!
Time ago on an interview someone (from D&D staff) said the intention is to create "solid" things.
Fog and smoke would be hard to discern... really hard since there is no "physical interaction". Although I don't think this would break anything.

[Aimeryan]

I would state that a cloud is one object, in so much as we state that any divisible object is one object. The most obvious difference between a gaseous object and a solid object is that the gas's constituent components have far more flexibility in their motion relative to each other than of those of a solid's.

That said, even minor image can create multiple objects - one of the examples is that of muddy footprints.

[DrowPiratRobrts]

That said, even minor image can create multiple objects - one of the examples is that of muddy footprints.

Which would surely include some measure of illusory water to make it believable...water isn't solid, so it's not that much of a leap to jump to gas (gas is an object though, so long as object is roughly defined as an entity made of matter).

All this being said, thanks Wizards...you're really making it easy on us...

[Segev]

To be fair, "muddy footprints" could be created by a single "mud with footprints in it" object. But it is ambiguous. If it's outside, it can be that. But what of muddy footprints indoors? Those are definitely multiple objects.

[sightlessrealit]

To be fair, "muddy footprints" could be created by a single "mud with footprints in it" object. But it is ambiguous. If it's outside, it can be that. But what of muddy footprints indoors? Those are definitely multiple objects.

What if you make a floor with muddy imprints. That would be one object.

[Segev]

What if you make a floor with muddy imprints. That would be one object.

Good point! Just overlay it on the existing one!

[NotPrior]

That said, even minor image can create multiple objects - one of the examples is that of muddy footprints.

A related question, does that mean an illusion can dig into a real object? Can you create an illusory hole which is apparently real to multiple perspectives (no shifting 3d perspective targeted to one person shenanigans) since a footprint in mud is inherently a small hole/dent in the ground? Or do you have to subtly build up the mud around the footprints to create the impression of it going into the ground?

I appreciate this sounds pedantic but being able to create an illusory chasm would be very useful. It also would let you turn invisible using any illusion large enough to cover yourself.

[Pex]

The problem with illusions is that DMs metagame it. Years of experience has shown this, regardless of edition. When an NPC uses an illusion, the DM does not say so to the players. They have to figure it out for themselves. When the player uses an illusion the DM always knows. He has to, but some DMs can't separate that knowledge from NPCs. He can't have NPCs waste their actions as if the illusion was real as players would do when the NPC uses the illusion. The knowledge of the illusion breaks the illusion,

Secondly, DMs don't want players to get away with something. Wall of Stone is a 5th level spell. Silent Image is a 1st level spell. Be a 9th level spellcaster casting Wall of Stone. The bad guys will take the time to walk around it. Be a 1st level spellcaster casting Silent Image of a stone wall, at worse one bad will use his action to investigate to prove it's an illusion to the rest of the bad guys who can then ignore it walking on through and make the spell useless.

When a DM argues a spellcaster cannot see through his own illusions, he doesn't want the players to get away with something. He precisely does not want a player to cast a line of sight blocking illusion that allows the party to attack the bad guys, shooting over the illusion wall to keep up appearances yet can still aim/target, but the bad guys can't attack the party because there's a wall in the way to prevent aiming/targeting. At best the party can have one round of this, but there will be an NPC to prove it's an illusion. An NPC will test that wall. The DM will find an excuse.

[Louro]

+1

This might be because playing smoke&mirrors is very different from hack'n'slash.
Illusions are meant to break the hack and slash. It's nothing more than a fancy and sophisticated form of crowd control, aside from other multiple uses.

Invisibility? Make a tree/wall and hide behind.
But what if you create a wall in a cave concealing the exit? Does it block the light?
Does the cave turn dark?

[Throne12]

Yes you see through your own illusion. Also so does anyone that knows it's a illusion.

[Segev]

A related question, does that mean an illusion can dig into a real object? Can you create an illusory hole which is apparently real to multiple perspectives (no shifting 3d perspective targeted to one person shenanigans) since a footprint in mud is inherently a small hole/dent in the ground? Or do you have to subtly build up the mud around the footprints to create the impression of it going into the ground?

I appreciate this sounds pedantic but being able to create an illusory chasm would be very useful. It also would let you turn invisible using any illusion large enough to cover yourself.No. You very much cannot. Hence why the "muddy footprints" are in illusory mud, or on an illusory floor where they take the form of mud smeared on said floor in the shape of a footprint.


The problem with illusions is that DMs metagame it.

This is one of the biggest reasons illusions don't work well for players, yes.

[Ganymede]

But what if you create a wall in a cave concealing the exit? Does it block the light?
Does the cave turn dark?

I've thought about this before, but I ended up just rolling all of this into the investigation check. Stuff like weird reflections, unusual lighting, missing shadows, etc., are the things someone will notice in realizing something is an illusion.

It is much less complicated than trying to imagine how illusions would actually work in the real world.

[Segev]

I've thought about this before, but I ended up just rolling all of this into the investigation check. Stuff like weird reflections, unusual lighting, missing shadows, etc., are the things someone will notice in realizing something is an illusion.

It is much less complicated than trying to imagine how illusions would actually work in the real world.

I like this. It also means that the higher level the wizard is, the better he is at making his illusion "fit in." No, he can't obscure the light to create darkness, but he can change how his screen looks to provide "explanation" for the light level.

[Willie the Duck]

I like this. It also means that the higher level the wizard is, the better he is at making his illusion "fit in." No, he can't obscure the light to create darkness, but he can change how his screen looks to provide "explanation" for the light level.

Now I'm picturing wizards attending Adobe IllusionShop (tm) seminars and entering worth1000 contests trying to make the most 'realistic illusions' (although 'who can make the most convincing fictional creature' contest keep being stymied when people discover that there really are three-headed, two-tailed dragons in this world).

[Aimeryan]

No. You very much cannot. Hence why the "muddy footprints" are in illusory mud, or on an illusory floor where they take the form of mud smeared on said floor in the shape of a footprint.

If I follow the conversation here, this is regarding the realistic changing of perspectives when overlaying an illusion of empty space over say a floor? If so, I don't think this post will disagree with what either of you said, just expanding upon the topic in my own terms.


An illusion of empty space can be made via a black surface, however, you have the issue that you can only overlay the existing floor (you can't make the floor invisible); this doesn't look very realistic the moment you change perspective in 3D space because the illusion is 2D (i.e., where are the sides of the pit?).

If you want to fool someone with a 2D illusion you need to deny them the ability to change perspective. For example, you could make an image of a 3D well (or similar) on top of the floor with an open side facing the enemy (so they can see in); the 3D walls of the well will shield the 2D empty space on the floor from other viewing angles and so keep it looking realistic. Of course, a significant dip in the floor makes it all a lot easier, since the empty space can then legitimately be crafted from a 3D perspective.

If magical darkness is desired, say the Darkness spell, then a pure black sphere/cube/shape works fine since it doesn't need to look realistic. It would not break on physical interaction, either. Similarly, a 2D plane of pure black could easily be misconstrued for a portal.

[Tanarii]

No. You very much cannot. Hence why the "muddy footprints" are in illusory mud, or on an illusory floor where they take the form of mud smeared on said floor in the shape of a footprint.

Right. As soon as I read "muddy footprints" I understood it to mean "mud left on a floor after you walk across it, a footprint". It amazes me how many people seem to take it to mean "footprint shaped indentations in mud".

But thats because i approach it from the instinctive understanding that (most) illusions don't remove something that is actually there from sight.

Especially since trying to overlay it with a physical object will reveal it to be an illusion due to the physical interaction rule.

[Louro]

Back in AD&D illusionists (a rare kind of wizard) could create almost anything if they had seen/experienced it before.
The example was a cave collapsing above you, that would kill for you, if you actually survived one.

[willdaBEAST]

To me it's silly to punish the caster like this, or make them come up with a silly work around like "I create a stone wall with a tiny peep hole." As far as party members, I'd give them advantage on the investigation check if the caster mentioned what they were doing or if they were present when there wasn't a wall in the target location.

There's a giant gap in logic when physical interaction will reveal it to be an illusion, but knowing that you made the illusion isn't sufficient to recognize that it's an illusion.

[Vekon]

I can see through the magic trick to seperate my thumb from my hand, but I still see its effects.

Your hands and thumbs are a physical thing you can interact with. It's mundane. A magical effect is entirely different and cannot even be compared. Even as I type this I'm starting to think that you're just making jokes.


LOGICALLY, a wizard, especially one that SPECIALIZES in illusory effects should be able to know that the wall they create is an illusion, regardless of touching it or making a save, and be able to see through it.

[Tanarii]

There's a giant gap in logic when physical interaction will reveal it to be an illusion, but knowing that you made the illusion isn't sufficient to recognize that it's an illusion.
It reveals it, but that can be interpreted to me you know it to be an illusion.

The investigation check is a second clause, and that one specifically allows you to see through it.

In other words, it's entirely within a valid interpretation of RAW that physical interaction gives understanding that it's an illusion, but not the ability to see through it. It takes an intentional application of additional intellectual / deductive focus, represented by both an Action and a successful Intelligence (Investigation), to do that.

This is, of course, not an argument that casters still shouldn't be able to see through their own illusions automatically. Just pointing out that your argument appears to be based on one specific interpretation of two possible interpretations of RAW.

[willdaBEAST]

It reveals it, but that can be interpreted to me you know it to be an illusion.

The investigation check is a second clause, and that one specifically allows you to see through it.
That point is fair, but in my mind that is a strange interpretation of the spell's wording.

"Physical interaction with the image reveals it to be an Illusion, because things can pass through it. A creature that uses its action to examine the image can determine that it is an Illusion with a successful Intelligence (Investigation) check against your spell save DC. If a creature discerns the Illusion for what it is, the creature can see through the image, and its other sensory qualities become faint to the creature."

Those are clearly separate situations to me, they both result in the same end result. Physically interacting with it reveals it to be an illusion. If you don't physically interact with it, you can instead try to examine the illusion to recognize it for what it is. Once you discern that it's an illusion, it appear translucent. I don't see any justification for both conditions to be met, or for the intelligence check to be the only way to see through the illusion.

In my mind the debatable aspect of the spell would be, does witnessing failed physical interaction with the illusion satisfy the first condition? If an arrow passes through a stone wall, does anyone who sees that happen now benefit from a transparent illusion? That greatly diminishes the power of the spell, so personally I'd rule some kind of passive perception bar be set since facing is no longer a mechanic.

[Tanarii]

Whether the physical interaction has to be personally viewed, or personally done, or even done at close ranger personally (ie no arrows) is something that's hotly debated.

And of course whether or not you think physical interaction makes it go faint will greatly change which of those you think is the appropriate power level. If it doesn't, an arrow going through an illusion letting all observers know it's an illusion doesn't mean it looses all value instantly ... it can still hide something behind it.

[Maelynn]

I always took the 'see through' part of the spell description figuratively, not literally. As in, when you tell a person "I'm seeing right through your lies!". I took it to not be literal at all, that an illusion won't suddenly turn transparent just because you know it's there.

Personally, I go by how illusions are generally treated in various other sources like books or films or whatever. There's a secret base in the mountain, hidden by an illusionary rock face. If you don't know it's there, all you see is a solid piece of mountain that looks just like everything around it. If you do know it's there, you still see a solid piece of mountain - you don't just mysteriously see a gaping hole. However, if you were to put your arm through it, you'd notice it goes right through the rock. So you can step through it safely, even though you think you're passing straight through solid rock.

I'd go by that in the example of the wall cast between the characters and the enemies. The caster (and perhaps the whole party if they see him cast it or know he did) will see a wall, but know it's an illusion they could just walk through if they wanted. But they still see a wall. The enemy, however, will see a wall and think it's real. So they won't try to walk through it, because every sane person knows you can't walk through walls.