Roll under vs. DC

[stripes]

So I was wondering which was "harder" and it occurred to me that roll under is very tightly tied to the ability score while DC is only somewhat influenced by it.

Which only made me more interested in the difference, so I gave in and made a rough graph.

If you have a hard time with the labels the left side is chance of success (0 is "never", 1 is "always") the bottom is the ability score from 3 to 18. The grey curve is roll under chance, the purple is DC5, the pink is DC10, the green is DC 15, the blue is DC20.

[GnomeBoy]

I think I'm seeing "roll under" as successful all of the time if you have an 18 Ability score. Hurunh??

I use roll under quite a bit, because it's simple, self-limiting and makes different scores actually mean something. For variance, sometimes it's "make it by 2 or more" or things like that, but that's still really simple. And it let's players instantly understand their odds.

[stripes]

Brain fart; I was calculating it as roll under on 3d6 not on a d20 (and it was equal or under). I'll make another graph later, the d20version will have more of a straight line.

[GnomeBoy]

...and it was equal or under...

I think that's normally how folks do a "roll under" check.

Looking forward to v2.