D&D 5E Blade Barrier Math Question

[eryndel]

So, I had plenty of time to poor over the D&D 5th Starter Rules and Basic Rules pdf while traveling to an ASME conference this past week (important background on why I'm asking a math question ) and plotting a game for my kids. The only nit I had was in the dimensions of Blade Barrier. As stated in the basic rules, you can either make a linear wall of 100 ft by 20 ft (5 ft thick), or a cylindrical shell of 60ft diameter. Isn't that cylinder roughly 2x the surface area of the linear wall? (since circumference = pi*diameter)

I'll probably rule it to be a 30' shell in my games (seems fair for a 6th level spell). Unless there's a good reason I'm missing for the cylindrical area to cover a lot more real estate than the wall.

My apologies for worrying about a minor math nit... I blame the conference

 

[MarkB]

The spell doesn't have to work out mathematically - it's magic. It may simply be that a circular wall is more efficient to conjure than a linear wall, and can thus be of greater magnitude.

 

[Ruzak]

For a linear wall the blades have to go back and forth, changing direction at each end. For a cylinder they can continue to spin around (always counterclockwise). This is why the cylinder is more efficient.

 

[Henry]

First, a minor correction: To read something exhaustively is to pore over it. Apologies for my own pedantism.

But no, you're dead-on; however, the guiding principal should probably be utility for the power of the spell slot, in which case I'm not sure if most players would find it worth a 30' cylinder. Maybe 40 feet?

So, I had plenty of time to poor over the D&D 5th Starter Rules and Basic Rules pdf while traveling to an ASME conference this past week (important background on why I'm asking a math question ) and plotting a game for my kids. The only nit I had was in the dimensions of Blade Barrier. As stated in the basic rules, you can either make a linear wall of 100 ft by 20 ft (5 ft thick), or a cylindrical shell of 60ft diameter. Isn't that cylinder roughly 2x the surface area of the linear wall? (since circumference = pi*diameter)

I'll probably rule it to be a 30' shell in my games (seems fair for a 6th level spell). Unless there's a good reason I'm missing for the cylindrical area to cover a lot more real estate than the wall.

My apologies for worrying about a minor math nit... I blame the conference

 

[eryndel]

First, a minor correction: To read something exhaustively is to pore over it. Apologies for my own pedantism.

But no, you're dead-on; however, the guiding principal should probably be utility for the power of the spell slot, in which case I'm not sure if most players would find it worth a 30' cylinder. Maybe 40 feet?

You're quite correct Henry, and if I'm allowed my pendantism, you're allowed yours

I like the explanation on minimization of energy in the cylindrical shell configuration. Not that I want to mix my science with my fantasy too much, but it can explain the mismatch in surface areas.