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Simulationist Pitfalls: The Mixed Fidelity Ruse

Articles like this "Clunky Mechanics in 5E", "Flank You Very Much: Tactical Play in D&D", and others, start to address tactical, aka simulationist concerns in the new D&D Next / D&D 5e ruleset.  One particular rule, flanking, has been a controversial subject since the beginning.  I'm going to pick on this particular example to explore an important aspect of simulation, namely fidelity.  Simulation is one of the few areas I would consider myself an expert in, so I think this discussion is warranted.

Simulation is the representation of a specific system using a series of mathematical relationships.  Simulation allows us to predict the outcome of the system without having to have a real system.  Fidelity is the level of detail that we include in a simulation.  Up to a point, fidelity can decrease the uncertainty in the prediction we make.  At some point, however, too much detail in a simulation simply clouds the uncertainty of the result with all of the uncertainty in the parameters used as inputs to the simulation.  Picking the right fidelity is usually key when putting together any kind of simulation so the right answer can be attained with the least amount of resources of computation.

Mixed fidelity is when we simulate certain aspects in great detail while we gloss over the details in other areas.  Mixed fidelity is a danger, because the low fidelity uncertainty can easily swamp out the detailed simulation, resulting in an imbalance of prediction.  The result is a simulation that may not predict anything realistic.

So let's jump back to our example.  Back in D&D 3.5 / Pathfinder we could get a +2 attack bonus for flanking.  However, in both D&D 5 and 3.5/Pathfinder, there is no facing. Without facing, we can now start to get unrealistic scenarios like the following:
Here we have four blue attackers all getting flanking bonus off a single partner, the blue guy in the center.  The reality of the situation is that the blue guy in the center is in serious trouble and not a really good flanking partner.  No worries -- he's also getting a flanking bonus for all 4 of the red guys that can attack him from his 4 blue attackers.  Without facing, it's easy to see that flanking bonus becomes unrealistic.  And why does this happen?  Because we have chosen to include one high fidelity component, i.e. flanking, when we didn't include another element of similar element of fidelity, i.e. facing.

Ultimately, this is what makes rule systems like D&D 5e better.  They have eliminated some of the fidelity that was both overwhelming and unmatched in the rule system.  The new streamlined rules allow for complete segments of rules to be swapped in and out, per the DMG, in order to change the fidelity, while trying to balance the overall fidelity in each approach.  I think GMs need to keep this in mind as they start tinkering with rule systems so they an understand the pitfalls of various changes they may make.  I also think looking at this example illustrated the elegance of D&D 5e and how it has fixed some of the mixed fidelity pitfalls of previous editions.

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