Using fireball on a grid

[Doomwhispo]

Hello. We always play dnd using a grid. I read the fireball description. Am I correct that it would take up a 8x8 square assuming we are playing with a 5x5ft grid? So it basically affects 64 squares. Seems OP as he'll so I just wanted to double check

[Kryx]

Entirely depends what system you use - 5e prescribes none.

http://i.stack.imgur.com/AoXda.gif

Could be a good option. In that system it's 44 squares.

[Doomwhispo]

But it really should be a square no? I mean 20 ft diagonally is 4 squares as well. If you don't make it a square this means that someone standing withi the 20ft range diagonally does Not get hit

[N810]

I couldn't tell without the book weather is supposed to be a square or circle (radius).

[PeteNutButter]

But it really should be a square no? I mean 20 ft diagonally is 4 squares as well. If you don't make it a square this means that someone standing withi the 20ft range diagonally does Not get hit

That's the point. As mentioned 5e doesn't lay out a grid like previous editions so your DM is free to run it however he chooses, but most people I believe use the 3.5 version. The spell says 20 foot radius sphere, so if someone is further than 20 actual feat from it's center it makes sense that they are out of its AoE.

[MrStabby]

But it really should be a square no? I mean 20 ft diagonally is 4 squares as well. If you don't make it a square this means that someone standing withi the 20ft range diagonally does Not get hit

If they are within 20ft they do get hit. It is just that they can be outside of 20ft and within 5 squares.

[tieren]

My last DM made paper overlays for the various spell effects (circles/cones, etc...). caster got to position the effect as they wanted (within reason, cone had to start in casters square). if a target's square was completely or mostly covered the effect hit, if their square was mostly not covered (or not covered at all) it did not.

[TheFlyingCleric]

But it really should be a square no? I mean 20 ft diagonally is 4 squares as well. If you don't make it a square this means that someone standing withi the 20ft range diagonally does Not get hit

Thanks to geometry, the diagonal of a square is approximately 1.4 times the length of its sides. This is important; four squares is, when measured vertically or horizontally, 20 feet, but when measured diagonally its closer to 35 feet.

A commonly used rule (and one that's shown as an optional rule in the Dungeon masters Guide) for approximating diagonals is to alternate between 5 feet and 10 feet for each diagonal space moved. So when moving, the first space of diagonal movement costs only 5 feet of movement, but the next costs 10 feet, the next one 5 feet, etc. I suggest that you use this rule, if you're not doing so already.

You can apply that same rule to circular/spherical areas of effect, such as that of fireball. You can see examples of that with the red shapes posted by Kryx.

If you're not using that optional rule (though I highly recommend that you do!) then fireball is indeed an 8 by 8 square.

[Feuerphoenix]

But it really should be a square no? I mean 20 ft diagonally is 4 squares as well. If you don't make it a square this means that someone standing withi the 20ft range diagonally does Not get hit

No they aren't. As written in DMG and PHB, the first diagonal move is 5 feet, the second time 10 feet. The next one is 5 feet again, and so on. So there is a difference.

[Grubble]

No they aren't. As written in DMG and PHB, the first diagonal move is 5 feet, the second time 10 feet. The next one is 5 feet again, and so on. So there is a difference.


That is incorrect. According to the PHB (pg192) each square on a grid represents 5 feet.

There is an optional rule in the DMG (pg 252) describing the method you mention, but it is not the standard.

[Slipperychicken]

That is incorrect. According to the PHB (pg192) each square on a grid represents 5 feet.

There is an optional rule in the DMG (pg 252) describing the method you mention, but it is not the standard.

That's why the variant rules are there: so that if that level of detail becomes relevant, the GM may implement the more precise rules. Keeping them as variants is part of a compromise central to 5e's design philosophy: the 'default' game is much lighter and easier to use, but groups may use the more complicated ideas if needed.


For another example: The default encumbrance rules might be seen as overly generous, with no intermediate states of encumbrance. But if granularity in encumbrance effects (gradually reducing speed for instance) becomes important to your group for whatever reason, then you're meant to use the variant rule that fixes it instead of complaining that the default rules aren't what you want.