What's "real positioning"?
It refers to a game where the mechanics rely on knowing your actual position. That may take the form of a grid (as 3/4e) or free-form (as in some previous edition and wargame play, using rulers, etc.). In such games, you can (at least in theory) know with relative certainty the distance between characters A and B and attach a "real" value to it (30', 150 m , etc.) This is different from an "abstract positioning" system, where characters are only "positioned" narratively, and play often proceeds with some notes about a battlefield, rather than a map. Of course, there are also systems that are somewhere in the middle, often using "zones" or some other mechanical contrivance to differentiate character positioning.
That's, at least, the context we've been talking about for this conversation.
EDIT: and I forgot to mention that many people played pre-WotC editions without very strict "real positioning", including IIRC a section in Combat & Tactics that was basically a zone system.
And IMHO d20 boils down to both d20 + mod vs. DC and incremental advancement of some sort (your call of how big/small the increments are).
I think the main reason it's so popular it's that the same core mechanic is used for very diverse characters/archetypes/whatever.
I can't see how.
I mean, boiled down to the die resolution method (as you mention),
most mechanics
can handle any archetypes, because rolling the dice tells you very little about who, what, or why the roll is being made. To some extent "character/archetypes/whatever" are just flavor to justify the modifiers. I would point out that including "incremental advancement" does, in fact represent a limitation on the archetypes accessible (although that folks find acceptable most of the time for playstyle reasons.)
Now, that doesn't mean that all dice mechanics are the same. There are a wide variety that do a lot of weird things. So, some features of the "d20 + mod" roll are:
- linear distribution i.e. each increment mod increases the range and distribution of results equally.
- small relative value of smallest increment. A "+1" is only 5% of the total range of the die roll. (Note that this does not translate directly to a 5% increase in character capability.)
Which is different from a "d6 + mod" system (and yes, I have seen such a system in the "wild"):
- linear distribution and range increases.
- very large increment: a "+1" is 17% of the total range
Which is different from a 4dF + mod roll from FUDGE/FATE (same as 4d3-8+mod):
- Strong "bell" curve distribution i.e. you are much more likely to roll "+0" than "+4". Although the range increases linearly.
- large relative value of a "+1". Its 11% of the total range of the roll.
Which is different from a Storyteller die pool. Where your traits grant dice (d10s) to roll against a difficulty and you count the ones that beat it.
- Distribution - erm...a little hard to predict overall, but not for a given roll. No changes to range for a change in difficulty, but a large non-linear change in distribution.
- Non-linear changes in both distribution and ranges for each die added.
Which is different from the way Cortex+ (as in MHRP) does it. A "Roll and Keep" system, where you build a die pool with dice (of variable size) added to the pool to represent traits contributing to the character's attempted action, and keep 2 of them after the roll to determine success.
- Distribution? - I don't even know what dice you're rolling, plus you wouldn't necessarily want to keep the highest roll each time.
- Can't even tell how good a +1d4 is. Especially if, as in MHRP, rolling a '1' is "bad".
So each of those will affect all sorts of design for the rest of the system, since that's where the mods (or dice) are coming from. This impact is both from a mechanical design perspective
and a psychological perspective of the players. For instance, the d20 method rewards the accumulation of numerous stacking bonuses (generally speaking going from +0 to +1 is the same improvement as going from +7 to +8). Also, adding a +1 for something is (by itself) hardly notable. This has players hunting for bonuses, so such a system can handle books filled with sources of tiny modifiers (and rewards the publisher for providing them, especially with additional bells and whistles). In the d6 and FATE methods, a "+1" is fairly large, so its disturbing to play to hand out a "+1" item, but its also extremely rewarding to collect even a temporary "+2" bonus. The FATE method also seems to emphasize skill differences more, both as an effect of the smaller range
and the centrality of the distribution (a "+4" is much more rare than a "natural 20". The MHRP system has you going over your whole character sheet to find traits to build into an action, which means you need to reflect the character's traits in your resolution narrative. etc. etc.
The strange-in-a-marvelous-way thing, to me, is that these things don't depend on genre very much at all. I could see playing a "Vampire" style game using any of them. The same is true for Fantasy, Supers, etc. (In fact, I think each of those methods has at least one incarnation that can be played in that genre.) The difference ends up being reflected more in play styles and table flow, rather than genre trappings that can be attached to the mechanics. So, even if I can make a game of FATE provide a narrative that's indistinguishable from a similar narrative from a session of D&D, it will likely feel very different at the table. I can't say that I think "d20 + mod vs DC" has any particular advantage over the other ideas, except that its a D&D "Sacred Cow".
