D&D 5E Spells, Targetting, and Glass Windows

In my game last night the party was exploring a tech dungeon with a bunch of abandoned damaged labs with dangerous stuff unleashed inside, but also possible loot and notes the party might want. Each lab was air sealed but had windows so you could see inside and sometimes controls on the outside to run experiments inside.

The question comes up with what can a spellcaster do through a glass window? Line of sight but a transparent barrier between them and things inside.

Can a bard cast shatter or polymorph past the barrier to target a creature inside while safe outside? Can they misty step past the sealed door keeping the bad stuff locked in their lab, grab some loot and misty step back out?

In 3e and 4e line of sight versus line of effect were fairly defined.

I looked up the targeting section under spellcasting in the PH page 204 to try and parse out the 5e RAW.

TARGETS
A typical spell requires you to pick one or more targets to be affected by the spell's magic. A spell's description tells you whether the spell targets creatures, objects, or a point of origin for an area of effect (described below).
Unless a spell has a perceptible effect, a creature might not know it was targeted by a spell at all. An effect like crackling lightning is obvious, but a more subtle effect, such as an attempt to read a creature's thoughts, typically goes unnoticed, unless a spell says otherwise.
A CLEAR PATH TO THE TARGET
To target something, you must have a clear path to it, so it can't be behind total cover.
If you place an area of effect at a point that you can't see and an obstruction, such as a wall, is between you and that point, the point of origin comes into being on the near side of that obstruction.
TARGETING YOURSELF
If a spell targets a creature of your choice, you can choose yourself, unless the creature must be hostile or specifically a creature other than you. If you are in the area of effect of a spell you cast, you can target yourself.

I ruled that the window was a barrier and meant total cover which blocked targeting the creatures or areas past the barrier but that misty step targeted the caster and they could teleport past the barrier.

Is this how you would interpret the 5e targetting rules or something different?

Is anything else RAW applicable?

I rule the same for the same reasons. Some things like misty step work to get you past that barrier because the target is the caster, the destination is somewhere they can see.

Total cover is total cover, Transparent or otherwise.

But then, I don't remember off the top of my head if 5E is smart enough to differentiate between cover and concealment.

There is a Sage Advice about this:


I know Sage Advice is not always the best advice, but I thought I would put it out there.

I would rule that a spell capable of destroying cover could target something beyond it. Like say, hurling a lightning bolt at a glass window, which should shatter and explode due to being a poor conductor of electricity (assuming such processes work in one's campaign).

Rabulias said:

There is a Sage Advice about this:

Is a glass window considered a total cover?

D&D Sage Advice · Is a glass window considered a total cover for the purpose of targeting a creature with Hold Person spell?

www.sageadvice.eu

I know Sage Advice is not always the best advice, but I thought I would put it out there.

Click to expand...

Just note that this is a tweet, not considered "official" sage advice. For that go to https://www.dndbeyond.com/sources/dnd/sac/sage-advice-compendium, which does not cover this.

Were it me I'd say it depends on the spell.

Where nothing physical travels from the caster to the target as part of the spell e.g. Hold Person or Shatter I'd allow it to work. Where something physical is involved, however, such as with Fireball and its little bead of guano, the spell wrecks on the window.

Reynard said:

Total cover is total cover, Transparent or otherwise.

But then, I don't remember off the top of my head if 5E is smart enough to differentiate between cover and concealment.

Click to expand...

I used to teach cover and concealment during patrols (in the military). D&D sometimes drives me insane...however, when I explain to my players my rulings, they go "makes sense" and carry on.

Just for explanation so others understand why it bugs me:

Cover is protection from fire (i.e. guns).
Concealment is protection from observation. They may not know you are there.

So if you are crawling through low grass, you have concealment, so you might not get shot at.
You do not have cover, because grass does not stop machine guns, and if they sweep the area with grazing fire, you will get hit. (most likely)

The glass window Sage Advice explanation never felt right to me. Like, I understand it. I get why they draw the line they draw but it seems counterintuitive.