What does a cone look like when fired straight down?

[Elricaltovilla]

What kind of area does a cone shape cover when fired from above at maximum distance? Would it look like a circle on the ground map or a line or what?

[Vaz]

It's a Cone. Yes, it's a circle.

[Jeff the Green]

A point, actually. It's not so much a cone as an eighth of a sphere, so at maximum distance it'll only hit one square (depending on exact size, thanks to rounding error).

[dascarletm]

Yeah, If horizontal cones ended up looking like triangles on the grid, you would get a circle. However they are merely pieces of a sphere in actuality as Mr. Green stated

[Elricaltovilla]

So then if you had a 30 ft cone, how far above the area should you be to get "maximum coverage" and what size would the area of that coverage be?

[da_chicken]

Well, look at the shape of cone areas:

http://i.imgur.com/f9JDZ.jpg

It looks like it would be a 10' x 10' area to me.

[Jeff the Green]

So then if you had a 30 ft cone, how far above the area should you be to get "maximum coverage" and what size would the area of that coverage be?

~20' up and a circle 40' in diameter.

Edit:
The way you get that is dividing the "size" of the cone by SQRT(2) to get the distance from the ground and multiplying that by 2 to get diameter of the circle.

[Vaz]

Draconomicon has lots of lovely information on breath weapons. There is a topic here (http://www.minmaxboards.com/index.php?topic=3594.0) which has a lovely picture detailing cones (ignore the rest of the rules, they're homebrew, but the picture is correct). On an Orthagonal angle, as the text puts it, the maximum width of a 30ft Cone is 8 squares, or 40ft wide, which occurs at 20ft out.

The widest points are as follows;

15ft Cone, Widest point @10ft, Covers 20ft
20ft Cone, Widest point @15ft, Covers 30ft
30ft Cone, Widest point @20ft, Covers 40ft
40ft Cone, Widest point @30-35ft, Covers 50ft
50ft Cone, Widest point @40ft, Covers 70ft
60ft Cone, Widest point @45ft, Covers 80ft
70ft Cone, Widest point @50-55ft, Covers 90ft
80ft Cone, Widest point @60ft, Covers 110ft

There is a rough pattern you can work off.

In this instance of a 30ft cone, it would be a 40ft diameter (20ft radius) circle.

There are a couple of ways to do it. Basically, if playing on a battle grid, I do it where provided the radius includes a square, it's hit by the effect. I think that's RAW, but cannot check. That's basically the majority rule listed here (http://www.superdan.net/gaming/dnd3/spellar/spellar1.html) - use the "Radial Areas (Centered on an Intersection of Lines).

[OldTrees1]

So then if you had a 30 ft cone, how far above the area should you be to get "maximum coverage" and what size would the area of that coverage be?


Well, look at the shape of cone areas:

http://i.imgur.com/f9JDZ.jpg

It looks like it would be a 10' x 10' area to me.



Size of Cone
1520304050607080
Distance to maximum shadow
10152025-30354045-5055
Radius of maximum shadow
1015202535405055


@Vas you got some of the distances wrong I think

[StreamOfTheSky]

I've always just liked to think about it as "the diameter at the ground equals the length of the cone" so if you have a 60 ft cone and point it downwards from 40 ft up, it'd be a 40 ft diameter (the rest of the cone is blocked by the ground and "wasted") circle on the ground, and for each 5 ft cube in height you go up from ground level, the diameter shrinks by 5 ft.

I am aware that's not the correct RAW way cones are shaped, but...conic shapes in D&D are just crazy and weird and it hurts my head trying to think about them too much.

[OldTrees1]

I've always just liked to think about it as "the diameter at the ground equals the length of the cone" so if you have a 60 ft cone and point it downwards from 40 ft up, it'd be a 40 ft diameter (the rest of the cone is blocked by the ground and "wasted") circle on the ground, and for each 5 ft cube in height you go up from ground level, the diameter shrinks by 5 ft.

I am aware that's not the correct RAW way cones are shaped, but...conic shapes in D&D are just crazy and weird and it hurts my head trying to think about them too much.

This is a fairly good approximation. It fits the RAW maximum shadow almost perfect. It does end up enlarging the cone beyond the RAW maximum shadow but that is a reasonable cost for the ease of use.

[Vaz]

Yeah, go by Oldtrees1's maths', I fubar'd, spent too long judging the IC and staring at a screen.

[nedz]

In principle you should be able to generate any Conic Section, but by RAW you just get the quarter circle segment.

As to rounding, see the notes in my signature.