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SR6 Mana Barriers

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penllawen

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« Reply #60 on: <08-31-20/1258:32> »
New rule of thumb: RPGs should never require you to know the value of pi. (This extends my previous rule that they should never require you to calculate the square root of anything. Looking right at ya, GURPs.)

That said:

2x2 metre plane = 4 m2

Surface area of a 2 metre diameter sphere = 4*pi*r2 = 4*3.14*12 = 12.5 m2

Sphere of 4 m2 area has diameter = 2*sqrt(1/pi) = 1.13 m

Stainless Steel Devil Rat

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« Reply #61 on: <08-31-20/1300:36> »
New rule of thumb: RPGs should never require you to know the value of pi. (This extends my previous rule that they should never require you to calculate the square root of anything. Looking right at ya, GURPs.)

That said:

2x2 metre plane = 4 m2

Surface area of a 2 metre diameter sphere = 4*pi*r2 = 4*3.14*12 = 12.5 m2

Sphere of 4 m2 area has diameter = 2*sqrt(1/pi) = 1.13 m

I suspected it wouldn't take long for someone to provide the math :D
RPG mechanics exist to give structure and consistency to the game world, true, but at the end of the day, you’re fighting dragons with algebra and random number generators.

Xenon

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« Reply #62 on: <08-31-20/1445:19> »

markelphoenix

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« Reply #63 on: <08-31-20/1534:04> »
would r be 1 or 2? Given it is LxW on the wall example, I assumed diameter would be 2, making r = 1. Was actually hoping for an obscure prior edition reference of the numeric values 2x2 having a specific rule for how they map to other shapes (i.e. for sphere, does r = 2?)

Sir Ludwig

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« Reply #64 on: <08-31-20/1536:40> »
Xenon,

I haven been putting to much thought into mana barrier. 

1.) Great site, thanks!

2.) I think a sphere would require you casting the very bottom a few feet under the floor/character. Otherwise your feet could be outside the barrier. 

3.) A Cylinder might be a better option for to trap/protection a humanoid.  I would say 1m r (radius) would be plenty (maybe 1m diameter if you don't move much and 2M (height)  From the same site: https://www.mathopenref.com/cylinderareamain.html

Best,
SL
Si vis pacem, para bellum

Xenon

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« Reply #65 on: <08-31-20/1555:57> »
Just make it into a series of 2x2 walls...

autXautY

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« Reply #66 on: <08-31-20/1613:01> »
Here're my approximations for surface area conservation
for a cube - edge lengths .8m for ever 2m the square would be (technically it's 2/sqrt(6))
for a cube without a top or bottom, edge length 1m for every 2m the square would be
for a cylinder or hemisphere, diameter 1.6 (cylinder has height .8m), for every 2m the square would be (technically it's 2/sqrt(2pi) and 1/sqrt(2pi))
for a circle, diameter 2.2m for every 2m the square would be (technically it's 2/(sqrt(pi))
for a sphere, diameter 1.1m for every 2m the square would be (technically it's 2/sqrt(4pi))

for a rectangle of height 2m, the length is half of the square of the ordinary side width (so 2m, 8m, 18m, 50m).
« Last Edit: <08-31-20/1616:55> by autXautY »