Wally DM

I Cast Fireball

A major rule you will come across a lot is something called Area Of Effect(AoE). I will only be covering grid based maps and not hex based maps. The rules here are based on 5E and the images that follow come from Xanathar’s Guide To Everything. Other RP systems may have different rules than listed here and are beyond the scope of this article. This article is meant to help those playing in person. Most virtual tabletops have tools added in to deal with AoE.

Lines, Cones, Circles, Spheres, Cubes Or Cylinders?

In D&D 5E, there are different coverages for spells. This list mostly applies to spell effects but things like a dragon’s breath attack can follow these rules as well. In addition to the 6 AoE listed in the header, there is also the range/target of self, and touch. This is important because all spells have a point of origin and unless otherwise stated, cones and lines originated from the caster and are very important for measurements. Touch range requires you to be within 5 foot of a target or “melee range”. Also note that even though the maps are a 3D space, you may be playing on a 2D map, vertical measurements may be needed to deal with flying enemies.

Tools?

At minimum you don’t need tools to measure, as you can easily count squares on the map. If you don’t have grid lines, a ruler is your best option. For different shapes you can measure and cut out paper, or clear paper sheets. Xanathar’s guide suggests using D6s to form the shapes or lines as well. There are several pre-made options if you shop around on-line to really speed up your games as you don’t have to take time to measure. It is easy to make your own reusable templates and decorate them as you see fit.

Draw The Line

The easiest AoE is a straight line as long as it’s along the X or Y axis, you simply count from where the caster is, out to the total feet listed in the spell. Diagonals get very complicated as do odd angles. Most electrical based magics tend to use a line.

Keeping in mind that standard maps use a scale of 5 feet for every grid space. If your line is 30 feet long and 5 feet wide, you count out 6 squares. Follow the rules listed on the spell and everyone on that line must make the appropriate save or action as needed. A thing to note here is that walls or obstacles can block the full AoE. These attacks tend to stay in the boxes but they can straddle between two squares and as long as ¼ to ½ of the box is covered.

An example of a 10 feet wide line.

Cones Without The Rods

Cones are something dragons know all too well and they are tricky because we are dealing with 2 lines now. Cones can be on average a cone of 30 feet or 60 feet.

You start still focused at the caster and measure out 6 spaces forward just like the line. If you are using a ruler, shift it to the left or right, aligning the edge of the ruler to the corner of the square infant of the caster. Make note of where the line falls and do the same for the opposite corner. This is the easiest way to get the perfect cone shape.

In this screenshot, dice are used to form the cone. In this example an angle is much easier to figure out. In the straight cone the dice are staggered to provide the full cone area.

Circle, Circles, Dot… And Cylinders & Spheres.

Circles, domes, spheres, and cylinders are all measured from the point of origin directly centered in the shape. If you remember your geometry, you will double the number listed. A radius of 10 means you will count out 2 squares in every direction. Cylinders, domes and cylinders have height to worry about as well.

So Square

Lastly, cubes are similar to circles except the point of origin is on a corner. Above is a 20 ft cube. These also have height to consider. The second example shows the area disrupted by an obstacle.

Concluding the Geometry Dash

There’s a lot of information to keep track of and this is something that can trip up anyone and slow down games. As a tip, these AoE do not need to be directly lined up with the grid to work.

I hope you enjoyed this article and as always leave a comment here and join WallyDM’s discord to join in the conversations.