View Full Version : Thunderwave spell, positioning of cube shape on a grid

November 17th, 2014, 22:22
This came up in a game Sunday, just wanted to get an exact explanation of positioning the cube for the Thunderwave spell on a 5 foot grid map. How is it positioned with a 15ft cube on a 5ft grid map?

Is the cube centered on the caster? Is the cube in front of the caster? Is the cube wherever he wants? Is it in front of him but on the face of the cube 15ft from him and every enemy within the 15ft is effected? So starting 15ft from the caster on the face of the cube and working back to the caster, which is what we went with since it says sweeping out from you, and enemies in the cube.

I read this debate on the link below, I guess there are several thoughts on how exactly it is used. Please only reply if you know for sure without speculating, since we are already doing that :confused:

I think this topic would be a great video for the vid guys, along with all the other shapes of spells.


Thunderwave Spell
1st-level evocation
Casting Time: 1 action
Range: Self (15-foot cube)
Components: V, S
Duration: Instantaneous
A wave of thunderous force sweeps out from you. Each creature in a 15-foot cube originating from you must make a Constitution saving throw. On a failed save, a creature takes 2d8 thunder damage and is pushed 10 feet away from you. On a successful save, the creature takes half as much damage and isn’t pushed. In addition, unsecured objects that are completely within the area of effect are automatically pushed 10 feet away from you by the spell’s effect, and the spell emits a thunderous boom audible out to 300 feet.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage increases by 1d8 for each slot level above 1st.e spell

Moon Wizard
November 17th, 2014, 22:44
There seems to be a lot of opinion from the couple of places where I saw this discussed. As in most 5E instances, it's completely up to DM in situations like this.

The wizard in my play test group will be very happy, since I originally ruled that it had to be centered on him which he found to be generally useless (i.e. he had to expose himself in middle of melee and try not to hurt allies). Given all the reading, I think I'm going to go with the close blast 3 interpretation (i.e. 4E style) from here on out for my group.


November 18th, 2014, 00:52
That's it then! for my group at least, thanks for the confirmation, It is still good for the player because the 15 ft are in front of him and not centered, and it still adhears to the rule that it emanates from him. If anyone wants to visualize it go to this link for close blast 3 which works great with Thunderwave.
Thanks MW :)

November 18th, 2014, 03:58
Cube area spells are a little weird, at least from a 3.5 player's perspective, because their origin is on one side of the shape. The 4E comparison picture pretty well covers it accurately. For a more official explanation, from the 5E PHB, pg 204:

You select a cube's point of origin, which lies anywhere on the face of the cubic effect.

As noted, the range for the origin is self, so effectively these combined mean you can place the cube anywhere such that any part of one edge (probably including a corner, but the GM could potentially get particular about that) is located somewhere on the caster's space. Generally this will be on the edge of the caster's space and aligned with the grid, but there's no rules reason I know of that it can't be skewed. It's just simpler to put it with the grid. As for moving targets away, the GM and player could probably decide between moving straight away from the caster/origin (more to the letter of the spell description) or straight away from the side the origin is on (easier to do on the grid).

November 18th, 2014, 05:02
whatever is ruled by the gm, it just need to be consistent through and through for the life of the campaign. i would go with whatever the gm rules.

academically speaking, one may approach this as:

1. sound -- in this case, thunderwave -- could be imagined as detonated explosives, emanating from a point, sending the sound waves indiscriminately and equally in all directions (assuming nothing blocks its path in any direction :-P).

in this case, the "cube" emanation visualization makes no sense except for game mechanics, i.e. setting the limits of squares/creatures affected by the spell. i imagine during brainstorming for 5e development, wotc decided "sphere" proved too egregious due to reports of arguments breaking out mid-game to figure out what square (and how much of it) would be caught within (or without) the sphere. i digress...

with this ruling then, A wave of thunderous force sweeps out from you. Each creature in a 15-foot cube originating from you... would have to be interpreted as the caster plus all squares immediately adjacent to him -- e.g. linearly speaking: 1 square in front + his originating square ("from you") + 1 behind him = 15 ft. -- are affected. this makes the spell worse than useless. hey - they created a melee spell!

2. waves -- in this case, thunderwave -- could be imagined as single-directional, like a laser beam (light/heat waves) projecting from one point, emanating away from that point. in this case, the "beam" is more wide but has limited range. so, a ...15-foot cube originating from you... is like a fat "sound beam" projecting from one point (the caster), emanating away (15ft.) from that point. where it originate from the caster doesn't matter; however, the cube does need to be adjacent to the caster's square.

to support that last point, 5e phb's definition of the cube area effect states: You select a cube’s point of origin, which lies anywhere on a face of the cubic effect. The cube’s size is expressed as the length of each side. A cube’s point of origin is not included in the cube’s area of effect, unless you decide otherwise. (illus, p. 204)

the other thing about all this is the infancy of 5e and wotc's attempt to simplify/streamline ruling (notice the "quick build" sections in every class, and the rule to rule all rules: "specifics beats general") to move the game along. without objective and standardized definitions, phrases like "emanating from you", "originating from you", and "sweeps from you" are ambiguous and meant for flavoring. the interpretation becomes subjective: i.e. emanate from you -- as in you being the originating square, like an aura; or originating from your hand, which can be directed in any direction? or sweeps from you -- as in like a broom with a narrow path; or a fan with a wide swath?

anyway, i digress again... :-P

November 18th, 2014, 07:12
Yep, I agree with your #1 point centering the caster in the cube makes the caster to vulnerable. Your number 2 point is inline with what makes more sense to me and like the picture above. I imagine a clap of the hands in a certain direction and the the waves go in that direction effecting creatures in a fifteen foot grid square/cube in front of the casters square in the direction the caster chooses. So lncluding the casters square it's 20ft for our campaign.

El Condoro
November 18th, 2014, 08:24
Another discussion source (without a definitive outcome) (http://community.wizards.com/forum/rules-questions/threads/4154491)

November 18th, 2014, 18:09
Another discussion source (without a definitive outcome) (http://community.wizards.com/forum/rules-questions/threads/4154491)

Very interesting conversation El Condoro thanks. I do disagree with some of them saying the caster can't be pushed also if he wants to be. For instance I can imagine a caster needing to get up to a second story window, so claps his hands downward towards the ground targeting the top part of the cube, the cube rotating underground, and launching himself upwards towards the window ledge:ninja:

He will probably wake up and aggro all the neighbors, and he better make his Dex check on the window ledge or fall to the ground taking bludgeoning damage :p

November 19th, 2014, 00:05
I have allowed the wizard to place themselves either on a corner or a face of the cube.