What is the volume of a Fireball?

[Hypersmurf]

My group has definitely house-ruled volumetric fireballs, but then, we've got a physics major and a physics minor in the house, so we love doing that kind of math. Our fireballs fill tight corridors for quite an extensive distance.

Yeah - many people tended to forget that even on a wide-open plain, a volumetric fireball tended to expand a quarter larger than its listed radius... since you generally cast it centred at ground level, so you get a hemisphere with the same volume as the theoretical sphere...

-Hyp.

 

[Methos of Aundair]

I've always felt the fireball spell should be expanded due to specific conditions. Such as casting it in a 5' hallway, or into a 20' square room that the pc's are not in. I never understood why they wouldn't expand. The problem arises though when players state things like "I'm going to put the point of origin as close to ground level as possible, so the fireball will expand outward since it is unable to go below the ground." This makes sense, since effectively you would only be creating half a sphere, or hemisphere. I believe this is WizCo's reasoning, rather than recalculating the area of effect due to terrain conditions, it simply covers a 20' radius spread, no matter the conditions. It makes things easier, though not logical.

 

[Asmor]

Hehehehehe...

This thread gave me a fun idea...

Gnomish cannon.

Very, very heavy iron/steel/adamantium/whatever chamber, of say 3' radius, totally enclosed except for a 1' tunnel.

Same basic concept as a gun or rocket engine. Toss a delayed blast fireball down there, throw a cannon ball in after it, and wait.

Actually, might make a good engine for an airship, if they can manage to keep from blowing themselves up.

 

[MarauderX]

If you want to get technical per the RAW, the volume is exactly 23,000 cu. ft.

Here's a hemisphere, using the diagonals rule:

   oo
 oooooo
 oooooo
oooooooo
oooooooo 44 x 5' cubes = 5500 cu. ft. 
 oooooo
 oooooo
   oo


     
  oooo 
 oooooo
 oooooo 
 oooooo  32 x 5' cubes = 4000 cu. ft.
 oooooo
  oooo 
     

     
       
   oo  
  oooo  
  oooo   12 x 5' cubes = 1500 cu. ft.
   oo 
       
     

     
       
       
   oo 
   oo    4 x 5' cubes = 500 cu. ft.

Multiply that by 2 and you get 23,000 cu. ft.

Rounding out those diagonals really makes you lose volume. I'll have to lodge a complaint with Wizards...

Andargor

I get 17,500 your way. You don't multiply by two, as the midsection only occurs once.

 

[BSF]

The main problem now is proving this in layman's terms to a DM who flunked geometry... I wish I had a 3-d hologram map.

Tabletop RPGs of the future will rock.

One word for you - Legos

 

[The Souljourner]

I get 17,500 your way. You don't multiply by two, as the midsection only occurs once.

Actually, you do, because you always place the origination point on a vertex of the grid (in this case a 3D grid).

Turn the 20' area on it's side and pretend the midpoint of the (now vertical) circle is on the ground. You'll see that there's just as much area above as below.

Besides, I already mentioned his charts were a bit off. Assuming the 20' and 15' areas are correct, it comes out to 32,000 exactly, which is a pretty darn good approximation, given the granularity.

-The Souljourner

 

[Patryn of Elvenshae]

I get 17,500 your way. You don't multiply by two, as the midsection only occurs once.

Actually, it occurs twice.

Once just above the plain of the fireball, and once just below.

This happens because Fireball, being an area of effect spell, is centered on a grid intersection, rather than the center of a square.

Therefore, the "normal" fireball distribution's first slice is 20' in each direction and 5' thick.

The first layer below that is equidistant from the center, and so is still 20' in each direction and 5' thick.

The fireball is centered at, in Cartesion coordinates, (0,0,0), not (0,0,2.5).

 

[andargor]

Besides, I already mentioned his charts were a bit off. Assuming the 20' and 15' areas are correct, it comes out to 32,000 exactly, which is a pretty darn good approximation, given the granularity.

You're probably right, I just used the diagonals rule, and lowering by 5' radius at every slice. It's probably a bit different in 'reality'.

But it's a fun thing to do at work.

Andargor

 

[The Souljourner]

Yeah, well, their 20' radius circle is a little wonky...

Yuh yuh yuh. Know exactly what you're talking about. If our code built faster, I'd have less time to calculate the volume of a random D&D spell which, as has been pointed out, has absolutely no bearing on game play (not that it makes it any less fun to do).

-The Souljourner

 

[Christian]

... it's just that 95% of the time, it gets cast on a plane (flat surface, not the flying thing) ...

Geez, thank the gods for that. The airline security rules would absolutely suck to enforce ...

"Sir, is that bat guano in your carryon? ... I'll have to ask you to step over here, please. And don't make any sudden moves or arcane incantations."