I had originally posted this on the old BG forums, but I figure it's time to relocate it here.
I’ve been annoyed with the template illustrations for cones in the 3.5 books ever since I first laid eyes upon them. Diagonal cones always had a smaller area than orthogonal ones. The notable first big offender is the DMG template page, where the cone templates for Burning Hands are horrifyingly small. Thankfully, someone at WotC actually took the time to fix the orthogonal cones when they printed the Draconomicon. Unfortunately, they did not bother to adjust the diagonal cones to try and cover the same amount of area. And so I went and recalculated them in such a way as to make both as equal as possible.
The math behind the orthogonal cone actually treats those first 2 squares adjacent to the attacker (C) as if they were diagonal movement. Everything continues from there, with that logic bringing out the end result you see above.
Squares Covered
Cone Size Orthogonal Diagonal
15’ 8 6
20’ 14 11
30’ 28 24
40’ 48 43
50’ 74 67
60’ 104 96
70’ 140 131
80’ 182 171
But the same logic is also applied to the diagonal template, which only has a single square adjacent to the attacker (C). This throws off the calculations, resulting in smaller cone areas in all sizes. To fix this, one must simply measure the initial square as if it were the result of an orthogonal movement, and everything suddenly changes!
With this new template, the diagonal cones cover the same size area almost exactly.
Squares Covered
Cone Size Orthogonal Diagonal
15’ 8 8
20’ 14 13
30’ 28 28
40’ 48 48
50’ 74 73
60’ 104 104
70’ 140 140
80’ 182 181
As you can see, only the 20’, 50’, and 80’ templates do not exactly match, and even then, are a mere one square short. And as an added bonus, the diagonal cones actually look rounded!
