Alternity System Die Roll Macro

In the alternity system there is a variable degree of success based on attributes plus skill rank. Let me slightly explain for those that don't know. If you have 1 skill point in melee weapons and 12 strength you would have 4 outcomes to the roll with a 13 or less you would have a ordinary success, with a 6 or less you would have an good success, with a 3 or less you would have an amazing success. The d20 is effectively reversed where a 1 is a critical success and a 20 is a critical failure. Is there a way to run a macro on this where you could do some if statments to show success rate first of all. Secondly there is a variable die roll added or subtracted from the d20 each roll to increase or decrease the chances for success based on the difficulty of the task the person is performing.

I don't think this system is possible without the API (a mentor feature). The macro system does not have support for if statements. It can compare a roll to a value (for example: /r d20<13 would tell you "1 Success" if you rolled 13 or lower), but it can't compare one roll to multiple values ( /r {d20<13}<6 would tell you "1 Success" if you rolled 13 or lower, because d20<13 reports 1, which is below 6). You could do something like [[d20<13]] (Regular), [[d20<6]] (Good), [[d20<3]] (Amazing) , and treat the best result of the three as the "real" result (and if the best result is a 1, it's a crit). It's still 5% crit, 10% amazing, 15% good, 35% regular, but it does clutter up the chat a little bit.

I would use the second method. Much cleaner and similar to how I've handled advantage/disadvantage in D&D Next.

Just be aware that if you roll 3 dice and then pick the best (aka lowest) the chance for one of them being low is much higher. For example to get a failure you have to roll: First die 14 or higher, second one above 7+, third die 4+. That results in a failure chance of (0,35*0.70*0.85) = 21% instead of 35% as it should. Unless I misunderstand what you're trying to do there. Even if you say "Regular has to be a success, otherwise it's a failure. Then if Good is also a success it's a good success, and if Regular, Good and Amazing are successes are then it's an amazing", it doesn't work too well. You'll now have the failure probability right, but good and amazing are now too low. For Amazing Success you'd need 13 or lower on the first, 6 or lower on the second and 3 or lower on the last die. (0.65*0.30*0.15) = 3% instead of 15%. Hm, that gives me an idea. [[d20<13]] (Regular), [[d13<6]] (Good), [[d6<3]] (Amazing) and it would have to be like I said above, only if all 3 show 1 then it's a amazing success. If Regular and Amazing are but Good isn't, then it's just regular. If Regular is 0, then it fails, no matter what the other 3 show. I don't think you can automate that step unfortunately. It's not super easy to understand why, but the probabilities are still the same. 35% for failure, 35% for regular success, 15% for Good success and 15% for amazing success, just as it should be. (if you really wanna know I can try to do the math here for you) (Basically you already checked if it's 13 or lower on the first die, and only if it is you look at the second die, so you can now ignore 14+ on that one as those are impossible results, instead on a full d20. Then you see if it's also below 6, and so on)

Ok, because I was bored I tried around and actually came up with a formula that does it all in one. It's not pretty, but it works. [[ {d20<13} * floor( ( {d13<6+1} * (1 + {d6<3*0.5}) ) ) ]] It returns 0 on a failure, 1 on a regular success, 2 on a Good one, and 3 on an Amazing Success.

Thanks for all of the replys guys.