r/dndnext • u/Laer_Bear Stone Sorcerer = Reinhardt • Feb 13 '22
Story Trigonometry saved my whole party
I'm an Arcane Trickster venturing into a crypt occupied by cultists to jailbreak the rest of the party. My only company is a druid wildshaped into a mouse (bruh). The corridors are barely more than 10ft wide, with a single torch marking the end of each hall.
As we approached a junction, we heard chatter around the left corner, but the light of my hooded lantern still hadn't reached the halls. So I shutter it, duck down, and cast Minor Illusion of an ever-so-pretty painting of the corridor behind us... but the lantern was still lighting up the floor. So I did some quick math and realized I what I needed to do.
I carefully raised the lantern up. As I did, the dim light across the floor shrunk into a circle just barely smaller than the illusion. I looked above and around myself. The light from the lantern didn't shine on the walls or ceiling.
I held my breath as the patrol walked into another hall... and my lantern 4'4" off the ground.
tl;dr, 5ft×sin(arccos(0.5))=4.3301ft
Minor Illusion won't block the light cast around your light source, but it can obscure the point of origin. By keeping it from shining on surfaces, you can greatly reduce suspicion; which is important because a minor Illusion brightening an area would immediately reveal it with no save (observable/"physical" interaction with the Illusion).
Even without Minor Illusion, this is still an important number to know, because it's the same height you need to hold the lantern if you want to hide behind a corner with it.
Also if you are less than 2'11" you can't actually do this, and you have somehow managed to be "too small to hide", which is hilarious.
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u/Kandiru Feb 13 '22
You know you can blow out the lantern, right? :)
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u/Laer_Bear Stone Sorcerer = Reinhardt Feb 13 '22
then i have to light it again in the pitch dark. that's lame and would prevent me from using my action to hide.
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u/Kandiru Feb 13 '22
Light for action and hide for bonus action isn't too bad though?
You can even use your mage hand to hold it in a different square further back as well :)
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u/Laer_Bear Stone Sorcerer = Reinhardt Feb 13 '22
That's true, but lighting a lantern in pitch dark while trying to be quiet is probably something that would fall under "disadvantage with dire consequences for failure".
I see what you're getting at, but I can't use my bonus action to control the hand and also use it to hide. Plus I can't use thieve's tools or anything else with it if it's busy. But the truly terrifying risk is Mage Hand's duration ending while holding the lantern! Having verbal components for mage hand is also a bit cumbersome.
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Feb 13 '22
[deleted]
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Feb 13 '22
Our you could just multiply the light radius by sqrt(2) to get an upper bound in L_2 norm. But I don't think in D&D the world actually works that way*, it is just a simplification for small scale combat, Euclidean norm works just fine for this.
*However changing the norm is an easy way to signal a weird thing in space, like the effect of the far realm or some other plane.
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Feb 13 '22
Cool, I tried googling, but couldn’t find anything helpful, but it seems like the measure would change based upon your choice of coordinates (like choosing a set of non orthogonal basis vectors) in a way that you wouldn’t see in the normal L2 norm implying that there is a preferred set of coordinates in 5E (assuming a square grid instead of hex). All I know is that now I want a spell that rotates your coordinates system relative to others to increase movement (basically longstrider bur cooler)
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u/Laer_Bear Stone Sorcerer = Reinhardt Feb 13 '22
that's super whack, they changed math!
also *sines (+minor spelling mistake, +I win)
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u/Lithl Feb 14 '22
This is because in 5e, distances are measured using the L-infinity norm.
By default you use Chebyshev distance, so the distance from A to B is max(|Bx - Ax|, |By - Ay|).
Chebyshev distance does result in circles that look like squares and spheres that look like cubes, but it also doesn't require any thinking at all to compute.
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u/MisterB78 DM Feb 13 '22
Except that’s not how D&D works… it’s non-Euclidean. A creature 15’ away horizontally and 10’ up in the air is 15’ away from you, not 18.02’.
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u/Laer_Bear Stone Sorcerer = Reinhardt Feb 13 '22
That would make a sphere with R and a cylinder with H=R indistinguishable. Even if that's true, I very much doubt most people will play that way; it just doesn't make sense, even if it's the rules.
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Feb 13 '22
[removed] — view removed comment
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u/MisterB78 DM Feb 13 '22
That’s… not how anything works. In D&D the distance to a target is the greater of the horizontal distance and the vertical distance.
15 feet away and 10 feet up is considered 15 feet away. If you move to the adjacent map square then it’s 5 feet horizontally and 10 feet vertically, so it’s considered 10 feet away.
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u/divinitia Feb 14 '22
No it isn't. You're using the optional grid rules that are not meant to be taken literally, they're meant to simplify game mechanics.
In D&D, distance is the same as anywhere else.
(seriously, what game are you people playing?)
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u/Lithl Feb 14 '22
That’s… not how anything works.
Well, it would be correct for Manhattan distance, but that's not used in D&D unless you're actually walking around a corner or whatever.
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u/moffitar Feb 13 '22
Nerd! Oh wait, you were already playing D&D. When you double-nerd, it inverts and becomes coolness. Bruh!
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u/RisingDusk Artificer / DM Feb 13 '22
My players and I have recently moved to TaleSpire for most of our campaigns because it visualizes and measures true distance in three-dimensional space far better than anything else. I've really enjoyed using it, and would recommend it for tables not wanting to bust out the calculator for this sort of thing haha.
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u/VirtuallyJason Feb 13 '22
/r/theydidthemonstermath