How to get an easy 40ft radius from a 60ft cone

[ryeookin]

My google FU didn't show any other threads revealing this technique so I thought I'd share what I discovered on my own (there must be some others who thought of it though).

Anywho if you want to get a 40ft radius from a 60ft cone (such as cone of cold), you'll need to be able to fly (or fly spell). Fly 40ft off the ground and center youself above the area you want to blast. Now cast your cone straight down on those below. At the bottom of the 40ft, the cone hits its largest coned area of effect which will be 80ft in diameter (40ft radius).

Note: To make this even nastier if you used the mm feat "widen spell" and applied it to a 60ft cone you can create a 80ft radius (160ft diameter) blast radius from 80ft above ground casting the cone straight downwards. This allows one to pretty much fry an entire battlefield.

Archmage's ability to avoid certain squares for aoe spells works great with this tactic imho.

So does this help or did you figure this out on your own already too? :)

[Jeraa]

(Edit: After a bit of math and playing with a grid, looks like it does work. I was wrong.)

Also, Widen Spell does not apply to cones. Widen Spell increases a spells area, while the size of a cone is based on its range. And Enlarge Spell doesn't work, as cones don't have ranges of Close, Medium, or Long.

[Cruiser1]

Cones are as wide at their end as they are long. A cone 40 feet long is 40 feet wide total, not 40 foot radius. You would affect a 40' diameter circle this way, not a 40' radius circle.
No, it works because cones are wider than that. "A cone-shaped spell shoots away from you in a quarter-circle in the direction you designate. It starts from any corner of your square and widens out as it goes." (PHB page 175). A quarter circle cone is a 90 degree area of a circle when considered from the ground. At the end of the range, from side to side the cone covers a distance 1.4 x the range. For example, a 60 ft cone spans over 84 feet (from say the point 60 feet north of you to 60 feet west of you, if you aim the cone northwest). Fly up about 40 feet (or 60 feet divided by 1.4) and aim the cone downward, and you indeed get an 80 foot diameter area covered! :smallcool:

[Jeraa]

I corrected my post as you were typing. Do note, however, that you do not need to be flying for this to work. A cone always covers that area. Its just that most of the time most of the area is either the ground, or open sky.

[ryeookin]

No. Cones are as wide at their end as they are long. A cone 40 feet long is 40 feet wide total, not 40 foot radius. You would affect a 40' diameter circle this way, not a 40' radius circle.(Edit: Which, despite what I though, is not said in the book, so may be incorrect. A 40' cone affecting an 80' diameter circle doesn't sound right, though.)

Also, Widen Spell does not apply to cones. Widen Spell increases a spells area, while the size of a cone is based on its range. And Enlarge Spell doesn't work, as cones don't have ranges of Close, Medium, or Long.

Firstly you are mistaken that a cone (being cast straight forward, not on an angle) is as wide as it is long (in 3.5). As you can see from this pic here showing all the aoe blast radius templates (http://uploadpic.org/storage/2011/jeKZugZgUTmKNdpMQsXsxh7Q3.jpg) a 60 ft cone (not an angle cone) is clearly the widest at 40ft down the line.

Also, the key is not that it's a 40ft cone, it's a 60ft cone cast above the ground at 40ft up being cast straight down on those presumabley standing on ground level. Cast straight downwards from 40ft up it does hit a 80ft diameter (40ft radius) area.

As for "widen spell" I see it works on busts and "Cone of Cold" is a cone shaped burst. I guess it is up to who interprets what is written.. in my interpretation it is still a 'burst" just one shaped as a cone. Depends on your interpretation or dm I guess. I think it would fly.

[Jeraa]

As for "widen spell" I see it works on busts and "Cone of Cold" is a cone shaped burst. I guess it is up to who interprets what is written.. in my interpretation it is still a 'burst" just one shaped as a cone. Depends on your interpretation or dm I guess. I think it could fly.

There is no interpretation about it. Look at cone of cold again.


Cone of Cold
Evocation [Cold]
Level: Sor/Wiz 5, Water 6
Components: V, S, M/DF
Casting Time: 1 standard action
Range: 60 ft.
Area: Cone-shaped burst
Duration: Instantaneous
Saving Throw: Reflex half
Spell Resistance: Yes
Cone of cold creates an area of extreme cold, originating at your hand and extending outward in a cone. It drains heat, dealing 1d6 points of cold damage per caster level (maximum 15d6).
Arcane Material Component

A very small crystal or glass cone.


You can alter a burst, emanation, line, or spread shaped spell to increase its area. Any numeric measurements of the spell’s area increase by 100%. A widened spell uses up a spell slot three levels higher than the spell’s actual level.

Its area is listed as "cone-shaped burst". There is no numeric measurement in its area to double. Its a shape, but doesn't give it a size. Instead, a cones size is determined by its length, in this case 60 ft.

[ryeookin]

Hmm. I see good point. Technically that wouldn't work then as per raw it appears. The cone straight down works as advertised however.

Now as for a cone always effecting the full area, what do you mean? If you were on the ground and cast the same cone (CoC) with the same angle area template down it would only effect two square as I see it.

Assuming you are implying it's otherwise, what's your source if you don't mind me asking?

[Jeraa]

Only if you cast it down. I was talking about casting it normally. Horizontally, not vertically. The cone still covers the same area, but most of that either hits the ground, or goes off into the sky.

You don't have to fly and cast the spell down to affect an 80' diameter circle. The spell can do that if cast horizontally as well. But unless there are a lot of flying creatures there, only the area next to the ground actually matters. Most of the area is wasted, but its still there.

[ryeookin]

Ah, I see what ya mean. Technically if cast horizontally it would only effect 40ft above as assuming below you is ground (so it can't go expand down). However I see your point. :)

[nedz]

What you are doing is taking a conic section.
These can be circles, elipses or parabolas.
The one you are most used to using is called two-lines, and resolves to a circle-segment when filled.
You can also achieve a line or a point - though these are tricky unless you are fighting two dimensional opponents.

As for the maximum size of your circle - you can work this out by Pythagorus.
sqrt(60x60+60x60)/2 = 42.4 foot radius.

[Tokuhara]

Always remember: D&D technically is in 3 dimensions. So it may fill a 40' semicircle, but it also covers it in 40' in all directions. Hence why a flying wizard's Cone of cold affects a larger area than a non-flying wizard's

[Godskook]

So does this help or did you figure this out on your own already too? :)

This is standard Dragonfire Adept tech. Helpful for dishing out 60d6 AoE in the worst possible shapes.