D&D General "that you can see", "line of sight", glass, mirrors, ~clairvoyance, blindsight, and anything else.

[greg kaye]

... An object and the reflection of that object are two separate phenomena. ...

the image, the refracted image, the reflected image... at its most basic level, there is only one phenomenon, and that's light.
Light, from a subject, has either been emitted or reflected from that subject and, that light, by whatever subsequent route it takes (perhaps straightforwardly through air of consistent temperature; perhaps via boundaries between different substances; perhaps through sections of air with a temperature gradient; or perhaps via a reflecting surface) is still the same light. You still see the person or thing. You recognize them.
Sure there are different ways this can be interpreted but I guess that would be down to the DM and any other participants at a table involved in worldbuilding.

 

[Paul Farquhar]

^^Correct. When we see something, we see the light emitted by or reflected off the thing. It's the same light irespective of if it's path is direct, reflected, refracted or bent by gravity. The only place the image exists is on the retina of the observer.

 

[greg kaye]

^^Correct. When we see something, we see the light emitted by or reflected off the thing. It's the same light irespective of if it's path is direct, reflected, refracted or bent by gravity. The only place the image exists is on the retina of the observer.

Damn, I missed one.

 

[Hriston]

Hmmm...you're on to something here.

Had they wanted it to work such that glass blocked spells, wouldn't the bolded have been better worded as "A target has total cover if a solid obstacle completely blocks a straight-line path from you to it".

Change it to "all straight-line paths" and I think that would do it.

And I threw the word "solid" in there to leave open whether a blanket provides cover, or a few inches of water.

This relies on an understanding of how the word obstacle is being used, part of which seems to be "a thing that is capable of blocking or hindering attacks". If it can't do that, it isn't really an obstacle, is it?

How about this: open field situation (no cover anywhere), caster is in Darkness but is using clairvoyance on someone standing not far away but outside of the darkness. Does that count as "sight" for targeting purposes?

Yes, I believe it does because, as the spell states, "You can use the chosen sense through the sensor as if you were in its space."

 

[greg kaye]

Change it to ... and I think that would do it.

Which is a golden approach to any interpretation of rules as intended. What we have is rules as written (optional as that is) but we do our best with our reasoned takes.

This relies on an understanding of how the word obstacle is being used, part of which seems to be "a thing that is capable of blocking or hindering attacks". If it can't do that, it isn't really an obstacle, is it?

When considering the view of an obstacle as "a thing that is capable of blocking or hindering ...", considerations might also be given to the forms of impedance that might potentially affect the likes of healing word, feeblemind and, the potentially homing to target, magic missile.

If you can see the target and there isn't an obstacle of a form that is considered to be "capable of blocking or hindering" the effect, what do you do?

However, another valid question would be whether it would break mechanics to be able to cast the likes of feeblemind etc. despite a presence of a physical, intermediary obstacle.

 

[Hriston]

the image, the refracted image, the reflected image... at its most basic level, there is only one phenomenon, and that's light.
Light, from a subject, has either been emitted or reflected from that subject and, that light, by whatever subsequent route it takes (perhaps straightforwardly through air of consistent temperature; perhaps via boundaries between different substances; perhaps through sections of air with a temperature gradient; or perhaps via a reflecting surface) is still the same light. You still see the person or thing. You recognize them.
Sure there are different ways this can be interpreted but I guess that would be down to the DM and any other participants at a table involved in worldbuilding.

I'm not sure what you mean by "this", but if you mean this issue of the behavior of light in the real world that you've brought up, I don't think it needs to be interpreted at all. It's mere obfuscation. The game isn't concerned with photons or how optics work. The game is concerned with whether you see the target. Light is the means to see, yes, but that doesn't make light the target. The target is not the light that bounces off of it. So, yes, one sees by seeing light, but the game isn't concerned with that. The question is what you see by seeing light. Are you seeing the target, or are you seeing something else? The target and its reflection are not the same thing. The target is in one place, the reflection is on the surface of the mirror, which is in another place. To paraphrase @Umbran from up-thread, looking at the moon doesn't entail seeing the sun.

 

[James Gasik]

It occurs to me that "see" might not be accurate either. Senses such as blindsight or tremorsense might be able to allow, say, a Grimlock caster to target others with spells. I think by literal RAW this wouldn't work, but if so, it doesn't really feel right.

 

[Oofta]

It occurs to me that "see" might not be accurate either. Senses such as blindsight or tremorsense might be able to allow, say, a Grimlock caster to target others with spells. I think by literal RAW this wouldn't work, but if so, it doesn't really feel right.

Monsters don't have to follow the same rules as PCs. On the other hand, while we "see" because of the visible spectrum of light, I don't see a reason to limit it to that. After all, darkvision isn't normal sight, yet I don't think anyone says it can't be used to qualify for the "that you can see" clause.

 

[greg kaye]

It occurs to me that "see" might not be accurate either. Senses such as blindsight or tremorsense might be able to allow, say, a Grimlock caster to target others with spells. I think by literal RAW this wouldn't work, but if so, it doesn't really feel right.

I've got reference for the first bit. Blindsight fine but:

Tremorsense​

A creature with tremorsense is sensitive to vibrations in the ground and can automatically pinpoint the location of anything that is in contact with the ground. Aquatic creatures with tremorsense can also sense the location of creatures moving through water. The ability's range is specified in the creature's descriptive text.

My favourite spoof d&d spell has long been Find Feet - but, in regard to a person who is moving about, Tremorsense can be interpreted to do no more than that.

I'd personally consider that this would help most with spells/activities where there was no dependency on attack rolls - and I'll quote my fav. ref.s: healing word, feeblemind, and magic missile.

I'm not sure what a Grimlock caster is, but there might need to be a rationale for them gaining any heightened, so to speak, information from tremorsense.

 

[James Gasik]

I've got reference for the first bit. Blindsight fine but:

My favourite spoof d&d spell has long been Find Feet - but, in regard to a person who is moving about, Tremorsense can be interpreted to do no more than that.

I'd personally consider that this would help most with spells/activities where there was no dependency on attack rolls - and I'll quote my fav. ref.s: healing word, feeblemind, and magic missile.

I'm not sure what a Grimlock caster is, but there might need to be a rationale for them gaining any heightened, so to speak, information from tremorsense.

Oh Grimlocks are a naturally blind race in D&D, so they have blindsight and heightened senses to compensate; I don't know if they have been statted to have spellcasters in 5e, but I can certainly imagine them having shamans and the like.