Percentiles, what's it good for?

[virgil]

I actually don't know of a single system, except maybe a homebrew on this forum, that uses roll-over with their d% resolution.
Chaosium & Eclipse Phase are two of the more significant systems I know of in the market that use a d100. The former is well known as crap, and the latter is burdened with subsystems and Coleman warcrimes.

[...You Lost Me]

Absolutely nothing.

Sing it again y'all.

[Josh_Kablack]

I actually don't know of a single system, except maybe a homebrew on this forum, that uses roll-over with their d% resolution.

Rolemaster.

[wotmaniac]

I thought ChartRolemaster was d100+mod -> compare to chart?

[Username17]

I'll quote Wikipedia here, because it gives a more succinct rundown than I could.

An attacking combatant rolls percentile dice, adds his or her OB to the total, adds modifiers, and subtracts the defender's DB. The total is then applied to a table for the attacker's weapon. The attack total is cross-indexed with the type of armor (if any) worn by the defender and the result will be a number of concussion hits dealt, which are then subtracted from the defender's running total. If sufficient hits are dealt, the defender may go unconscious, but death seldom results purely from concussion hit damage.

In addition to concussion hits, however, a critical hit can be dealt by the result on the weapon table. These are described by type (slash, crush, puncture, etc.) and by severity (generally A through E, with E being the most severe). Critical Hits (or simply "crits"), can inflict additional concussion hits, bleeding (subtracted from concussion hits at the start of each new round), broken bones, loss of limbs or extremities, internal organ damage and outright death. If a crit is inflicted, a second roll is made on the appropriate critical table.

Needlessly complicated of course, but it is literally percentile roll over. No idea why the "roll over" is based on a series of charts rather than normalizing all bonuses such that your roll over target was 100, but whatever.

-Username17

[wotmaniac]

Well, that was about as clear as mud. I'm now reminded why I could no more than merely thumb through the books.

Besides, what would they then do with all those charts?
Duh.

[phlapjackage]

Warhammer Fantasy Roleplay?

[hogarth]

I actually don't know of a single system, except maybe a homebrew on this forum, that uses roll-over with their d% resolution.

The reason, of course, is that it's intuitive to interpret a skill range between 0% and 100% as your flat chance of success. If your skill is 50% and your target number is 130%, it's not really intuitive what 130% means in that context or that it equates to a 21% chance of success.

[Solmyr]

Warhammer Fantasy Roleplay?

That one has rolling under.

[Meikle641]

The reason, of course, is that it's intuitive to interpret a skill range between 0% and 100% as your flat chance of success. If your skill is 50% and your target number is 130%, it's not really intuitive what 130% means in that context or that it equates to a 21% chance of success.

I was under the impression that roll over was skill + roll vs TN 100. [Edit] How many systems actually list chance DC as 130% or whatever? Honestly curious.

EDIT: Meant to quote Hogarth, but was on a phone earlier. Also, added a bit of text.

[CCarter]

I think "Anima: Beyond Fantasy" is d100+mods.

[Username17]

I was under the impression that roll over was skill + roll vs TN 100.

That would be an obviously better way of doing things. Because then your total roll modifiers would be equal to your percentage chance of success. And it would still be way easier to do degrees of success or opposed rolls, because everything would come pre-normalized and you wouldn't need to do subtraction comparisons.

In practice, most d100 roll over systems use a floating target number like d20 does. I have no idea why they do this, when they could apply all target number shifts as bonuses or penalties to the roll instead and then have the previously discussed advantages.

Hell, Rolemaster not only goes with a floating target number, your target number is chart based. It's fucked.

-Username17

[OgreBattle]

riiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiifts

[Judging__Eagle]

I believe that Rifts is a mish-mash of D&D d20 + other Dice for combat + damage. Plus D% for skills.

Even having played it more than once; I can't remember clearly how it works.

Which is sad, because I learned how to completely break the Rifts magic limitations before the game even started with the first Rifts character I ever made.

This was a result of their being able to turn their existing magic energy into "mana balls" that could be drained for magic energy later (via a spell); turn their MDC into Magic Energy (via a spell); and then naturally regenerating their full MDC in ~5 minutes) they didn't have a "lot" of either magic energy or MDC; but the ability to create a power loop meant that they could have a backpack full of hundreds of points of magic energy before they arrived at their first combat encounter.

In the first adventure I was seriously considering blanketing a Coalition city with thunderstorms to give the party perfect cover; and completely wreck/ground any air support the CS would have sent in.

This would have cost in the 100's of magical energy to pull off (each Thunderstorm cost some large amount of mana as well; enough that casting more than one with my natural pool would leave me almost dry); but with the mana-storage spheres spell; kill-self for mana spell; and natural regeneration of health at stupid speeds; it was a viable option.

Their psychic energy was normal, but the powers picked where cherry-picked as all hell.

While the second character I ever made was a weaker than a vagabond human.

It really is a kitchensink, even down to its engine.

[hogarth]

I was under the impression that roll over was skill + roll vs TN 100.

If the target number is always 100, then you might as well be using roll under. Frank worries about doing match for opposed rolls, but the latest version of Chaosium has that covered well enough (whoever rolls higher and still succeeds is the winner).

[Meikle641]

Does Chaosium still require you to use resistance charts for opposed checks? I saw the kickstarter for the newest CoC but I didn't recall seeing any mention of edition changes.

[Username17]

I was under the impression that roll over was skill + roll vs TN 100.

If the target number is always 100, then you might as well be using roll under. Frank worries about doing match for opposed rolls, but the latest version of Chaosium has that covered well enough (whoever rolls higher and still succeeds is the winner).

You realize that that is bullshit right?

You're still reporting two numbers, degree of success and literal roll. That's objectively worse than using roll over TN100. In exactly the same way as THAC0 is worse than BAB, and for the same reason.

Roll under is an extra step, whether it be an extra math step or an extra reporting step (or both) as regards TN 100 roll over. It's mathematically identical, but TN100 roll over is provably superior.

-Username17

[Nath]

I don't find the extra step.

Roll over
#1 Add Skill+Modifier
#2 Roll D100
#3 Add (Skill+Modifier)+D100 Result
(#4 Trivial) Subtract 100-(Skill+Modifier+Result)

Roll under
#1 Add Skill+Modifier
#2 Roll D100
#3 Subtract (Skill+Modifier)-D100 Result

An addition is faster to perform than an subtraction, which is what would make Roll over faster than Roll under, not the number of steps.

Roll under can be faster in situations where the system or the gamemaster don't care for the degree of success, as simply comparing (Skill+Modifier) to D100 Result to see if it's greater or smaller is faster than any addition or subtraction. That's the typical case in games like Call of Cthulhu, where most roll results in either "story advances" or "story doesn't advance" (whether that's a terrible game design or not is another debate).

Another issue with Roll under is that it is counter-intuitive: people naturally tend to see larger numbers as better results than smaller numbers (unless your into numerology, in which case it becomes a lot more complicated). With Roll under, large numbers are good as skills but bad as rolls.

[Red_Rob]

Also, if you care about degrees of success roll over is easier.

Quick, you rolled 37 and your skill is 73, how much under are you?

Quick, you rolled 63+73 and your target number is 100, how much over are you?

Roll under is easier in the specific circumstance of "compare roll to skill, no modifiers". The more extras you add to this the more attractive roll over becomes.

[wotmaniac]

I don't find the extra step.

Subtraction is empirically and objectively harder than addition.

[Nath]

Which is the thing I meant when I wrote "An addition is faster to perform than an subtraction, which is what would make Roll over faster than Roll under, not the number of steps."

Subtraction is a more complicated and longer step than addition, but it is nonetheless still only one step (actually, four steps with two-digits number). Unless we delve into a bit of neurological science to count the number of neurons involved, the difference between addition and subtraction, and thus Roll over and Roll under, is not a number of step, it is the complexity and time taken to resolve these steps.

The fact that not all step resolutions are equal is a key factor in game design.

[wotmaniac]

Which is the thing I meant when I wrote "An addition is faster to perform than an subtraction, which is what would make Roll over faster than Roll under, not the number of steps."

My bad -- evidently I missed that part.

[hogarth]

I was under the impression that roll over was skill + roll vs TN 100.

If the target number is always 100, then you might as well be using roll under. Frank worries about doing match for opposed rolls, but the latest version of Chaosium has that covered well enough (whoever rolls higher and still succeeds is the winner).

You realize that that is bullshit right?

You're still reporting two numbers, degree of success and literal roll.

There's no degree of success other than "which number is bigger?". If you need to do subtraction to figure out which of two numbers is bigger, you're doing it wrong.

I think you're just confused as to how the system works.

[shadzar]

any system can, if you know the range and can do the math to exchange the die request for d%

[virgil]

There's no degree of success other than "which number is bigger?". If you need to do subtraction to figure out which of two numbers is bigger, you're doing it wrong.

I think you're just confused as to how the system works.

In which case, it's like blackjack, and the character with the smaller degree of success wins.