D&D 5E Minor Illusion question

[HammerMan]

Can an object created by minor illusion, which can't product sensory effects, block light?

Example: A room is lit by a torch in a wall sconce. Minor Illusion is cast to create an iron box bolted to the wall around the torch. Does this plunge the room into darkness?

If my arcane trickster runs down an alley and finds a cubby and casts minor illusion to cover the entrance with a wall, or opens a door and then casts it to make the door look like the wall... either way it blocks ME. if the light that reflects from me (how sight works) is blocked by the illusion then the light from the torch must be too...

this reminds me of an old school drow argument. I am in a huge room with a skylight, I cast darkness on the skylight blocking all the light...does that make my darkness now 'cover the whole room'?

 

[Crimson Longinus]

So if illusions do not block light, what does that actually look like then? They wouldn't cast shadows, right? What if there is brightly lit object behind the illusion? Can I see sun/torch/etc through the illusion even though that illusion is affecting me? Imagine if there is a room with where the only light source is a torch in an alcove. Illusory wall is placed to block the alcove. What does this look like? If it doesn't block light, wouldn't it be blatantly obvious that it is an illusion? Not that this necessarily is a problem. Perhaps there simply are some situations where illusion cannot feasibly be used.

 

[Gadget]

I find it useful to look at what someone is trying to accomplish when adjudicating illusion spells. Part of this is taking into account the level of the spell and affects compared to other spells of the same level. Minor Illusions do not move and cannot change the lighting conditions, IMHO. It cannot create light, or block it. It is not a poor man's light cantrip, nor a poor man's darkness (or a poor man's invisibility for that matter, in regard to all those who want to 'hide inside an illusory box and fight enemies that approach with the benefits of being unseen). The cantrip does enough as it is. Trying to overthink things and apply science and even--in some cases--logic to these things does not always bear fruit worth tasting.

 

[J.Quondam]

The problem with this is that it extends the influence of the illusion way too much around the landscape for such a simple spell, it's no longer a simple illusion of an object, but it influences everything someone in the same area believes to be lit or not.

No, there is no problem. You still haven't understood what I wrote. But I really don't want to get into one those nitpicky point-by-point slap fights so popular among certain people around here, so...
Cheers!

 

[Swarmkeeper]

If my arcane trickster runs down an alley and finds a cubby and casts minor illusion to cover the entrance with a wall, or opens a door and then casts it to make the door look like the wall... either way it blocks ME. if the light that reflects from me (how sight works) is blocked by the illusion then the light from the torch must be too...

"How sight works" IRL - and a simulation of "IRL" is not necessarily how all people run their fantasy RPGs. At our table, if your arcane trickster is carrying a light source well, sorry, that minor illusion is not going to block the light. If your arcane trickster is not carrying a light source then the illusion will conceal them.

this reminds me of an old school drow argument. I am in a huge room with a skylight, I cast darkness on the skylight blocking all the light...does that make my darkness now 'cover the whole room'?

At our table: The Darkness will block exactly a 15' sphere of light - as defined by the spell. Anything outside of that sphere will be lit as before.

 

[HammerMan]

"How sight works" IRL - and a simulation of "IRL" is not necessarily how all people run their fantasy RPGs. At our table, if your arcane trickster is carrying a light source well, sorry, that minor illusion is not going to block the light. If your arcane trickster is not carrying a light source then the illusion will conceal them.

why?

At our table: The Darkness will block exactly a 15' sphere of light - as defined by the spell. Anything outside of that sphere will be lit as before.

SO the light passes through the darkness?

 

[Crimson Longinus]

I don't necessarily need a fantasy world to follow real world physics but things should still work consistently and more importantly in a way that can actually be visualised.

 

[J.Quondam]

So if illusions do not block light, what does that actually look like then? They wouldn't cast shadows, right? What if there is brightly lit object behind the illusion? Can I see sun/torch/etc through the illusion even though that illusion is affecting me? Imagine if there is a room with where the only light source is a torch in an alcove. Illusory wall is placed to block the alcove. What does this look like? If it doesn't block light, wouldn't it be blatantly obvious that it is an illusion? Not that this necessarily is a problem. Perhaps there simply are some situations where illusion cannot feasibly be used.

Yeah, i think that makes sense. Using a cantrip to definitively block all light in a room seems beyond the capability of its 5ft volume, so yeah, I think that would look really strange, maybe a black box with light emanating weirdly from it, like a graphics bug in a videogame. For obviously "off" stuff clearly beyond the capability/intent of the spell, maybe allow an immediate save to see through it, possibly even with disadvantage?

Another thing to consider is what exactly the saving throw means. In the case of minor illusion, it doesn't have to mean the viewer is actually fooled; it just means they perceive the illusion as solid. So the viewer who sees the boxed torch and succeeds their saving throw, would see the torch with a ghostly box around it; while the one who failed the save sees a black box and can't see the torch. And both can agree they're in a lit room and looking at a janky illusion.

I don't necessarily need a fantasy world to follow real world physics but things should still work consistently and more importantly in a way that can actually be visualised.

I think the "graphics rendering" analogy is a good way to look at illusions. The glitches in a wonky illusion don't have to be consistent, just like there's no set way that a graphics bug is consistent. It just has to be "wrong". It's that potential for "wrongness" that makes the illusions in particular discernible from reality.

In general, though, I think it's a lost cause trying to really understand how illusions should really behave using real-world thinking, because they break so many real-world rules. I honestly think illusions might be more "problematic" from a physics standpoint than even teleports and fireballs.

 

[Crimson Longinus]

In general, though, I think it's a lost cause trying to really understand how illusions should really behave using real-world thinking, because they break so many real-world rules. I honestly think illusions might be more "problematic" from a physics standpoint than even teleports and fireballs.

I think what makes illusions super weird that they self evidently are subjective. Depending if they have discerned the reality of the illusion or not, two people can perceive the exact same illusion differently. If this was not the case, I think it shouldn't be too hard to just deem them some sort of light manipulation and have a coherent model for them. But that subjectivity really throws a wrench into the works. It makes me think illusions are ultimately messing with your mind... Which brings us back to whether illusions, even high level ones, can provide actual light. If illusions are just in your head, that shouldn't be possible. You might think you can see things, but you wouldn't actually.

 

[Fenris-77]

I might be tempted to rule that the illusory light source does cast light, but only within the maximum volume of the spell. So if Minor Illusion is 5x5 max then an illusory torch only cast light that far. It can be seen (I guess?) from anywhere, but in terms of using that light to see other functional things you need light for it only works inside the casting volume. Obviously that would look somewhat off in a dark room, maybe like the torch was dimmer than it should be, but that's cantrips for you.