Lightweight and Heavyweight Rulesets

Eric Heimburg recently wrote a very nice piece on how 4th edition D&D rules simultaneously reduce the value of loot and make it a part of the mundane mechanics. Brian Green picked up on this and took the angle of how this is a case of MMOs affecting the design of pen and paper RPGs instead of the other way around. He went on to discuss how modern MMO (and some PnP) rulesets are a consequence of the constraints of software logic.

I can see the logic behind this, but I have to disagree that all of the options must be hardcoded. Let me try to explain my position a bit further.

First edition Dungeons and Dragons (1E) was what I would refer to as a “lightwieght” ruleset. Sure, by the time the transition to 2E, those rules had grown to thousands of pages of supplemental material with a potentially complex, ponderous and schizophrenic ruleset. The point was that all of these supplemental rules were optional and the DM could cheery pick from them. In fact, the at least half of the original DM Manual was a codex of tips for DMs to run campaigns, more than a rules manual. In 1E, DMs were expected to either make up rules on the fly, use house rules or both. You could think of it as the common-law legal system used in Anglo-Saxon and Commonwealth countries; where law is messy, murky and based on precedent.

Computer based rulesets (and 4E D&D, though 3E already had a tendency towards this) by contrast, traditionally assume that whatever is not explicitly in the ruleset is disallowed. These are “heavyweight” rulesets that try to form a complete, self contained game. You could think of these as Napoleonic Code based legal systems, where the law is based on theory and tries to be predictive of the future. The problem is that you can’t predict everything and emergent gameplay will happen. Due to their complexity, heavywieght rulesets are also prone to emergent gameplay; but this is often of the “unbalananced” or “exploit” variety. The fundamental difference between a lightweight ruleset and a heavyweight one is that the former embraces – even requires – emergent gameplay while it is often a QA issue for the latter. The freeform emergent gameplay of lightweight rulesets requires a quick thinking GM.

Except that it might not.

Think of all of the different kinds of judgment calls that a typical GM made in old school pen and paper RPG sessions. I vividly recall a session that took place in San Diego a quarter century ago. A cousin and I had a ranger and a fighter in a low level dungeon. Another cousin was DMing. We were fighting a pair of goblins. I rolled a 1 on a two hit roll and the cousin that was DMing declared that my sword broke. Suddenly the situation looked desperate. We had just picked up a loot bag with two hundred copper pieces in it a short while before. So I announced that I would grab the loot bag and swing it around, wielding IT as a weapon. The next round, my playing cousin scored a killing blow with his weapon and the DM asked me to roll to hit. As luck would have it, I got a natural 20. My DMing cousin rolled some dice and then announced that I had walloped the last goblin so hard that not only did I kill it, but that the bag ripped open showering the corridor with coins.

Consider the kinds of judgments that my cousin had to make as DM:

  1. Was the bag wieldable as a weapon? His sense of naive physics told him that you could indeed wield a loot bag as a flail like object.
  2. His other judgment was that the burlap bag was not strong enough to withstand the stresses associated with impact and would rip open.

In short, he was making judgments about physics. Most GM judgments involve either NPC psychology (the AI) or physics. Can that PC actually swing from the chandelier and knock the NPC over? AI is hard. We have 50 years of AI research and precious little to show for it in terms of creating artificial personalities. Physics, on the other hand, is comparatively simple. Yes, you are reading me right. Physics is comparatively simple. What is not simple is the usual approach to adding more and more physics to games. It mostly consists of adding more and more special rules. This introduces complexity in a geometric fashion. The fundamental problem here that that the traditional reflex action is that of a “game designer”. The game-designer twitch moves us towards heavyweight rulesets.

This is a real (albeit paraphrased) conversation I once had about encounters for a NWN2 server:

Me: Y’know, we have a situation here where it is highly likely that we want no encounter to occur, an encounter to occur some of the time and sometimes there are a bunch of encounters. Why don’t we solve this in an elegant way using a Poisson distribution. Let lambda be the most likely number of encounters for a given area and something settable by the dev. K (rounded down) will be the actual number of encounters.
Other Individual: *looks at equation* no way! Too Complicated!
Me: Huh? One value set by the builder per area, one calculation and a nice fluidly scalable…
Other Individual: Okay, if the PC is below 10th level, then we use this table here. We roll a D6 and add one to the roll. If it is below 4, no encounter, above 6, multiple encounters. Then we roll on this table over here to see how many encounters there are. If the person is above 10th level, we add 4 and use a different table. If there are low levels traveling with high levels, we’ll add d6 to the original roll instead and then flip a coin on the table to use.

I am a software engineer by trade. By education, I’m a physicist. Physics is not about creating big, complex things, but rather simplifying and clarifying based on “first principles”. Depending on the level you detail you want to work from, there are perhaps two dozen fundamental rules that could use to describe the world around you. That world is the ultimate lightweight ruleset. It has no formal game rules. Everything is emergent gameplay from the physics. Chapter four is my far my favorite one in Bartle’s Designing Virtual Worlds.

It is possible to implement a platform where lightweight rulesets are viable on the computer. The first thing we need is a clean vocabulary for defining naive physics. As I said that the top of this post, this is near and dear to my heart. Memotica is all about making it possible to build the underlying physics of worlds in a clean way. The second and more important thing we need to do is get rid of the game designer paradigm and replace it with a “set designer” paradigm. A game designer creates a game. This is appropriate for someone creating a boardgame. A set designer is creating a themed space and the props to go with it where the kinds of gameplay that arise are not always explicitly created by the designer. As long as designers eschew realism in one breath and then add a hundred special cases to their heavyweight ruleset the next, MMOs will always have a “what not expressly allowed is forbidden” feel.


About Dave

I’m a 38 year old American who has lived the past 9 years in Germany and India.
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6 Responses to Lightweight and Heavyweight Rulesets

  1. You’ve fallen into the “Physics can solve everything!” trap. It’s a really beautiful delusion for some people. Physics isn’t easy to implement. Perhaps easier than human-like A.I., but that’s like saying I’m more sane than Charles Manson.

    The joke we had about Physics when I took my year in college was that the knowledge was invaluable, if we lived in a world with lots of infinite, frictionless surfaces and no air resistance.

    The main problem here is that once you start including something in the rules set, it is no longer as interesting or as fun. Would your story about using a money bag as a weapon be as interesting if the PHB had listed “burlap bag of 200 copper pieces” in the weapon table? Probably not. The same thing happens if you start taking a “physics” based approach to things. If wielding anything can work as a weapon, then everything gets considered as a weapon in a game. If a bag of coins does better damage than a longsword, I might use a bag of coins as my primary weapon. (I might get a stronger material for the bag, though.)

    Also, consider what the GM in your example did when he ruled about the bag splitting open. He wasn’t just applying physics, he was considering what would make an interesting scenario. The image of hitting a goblin over the head with a bag of coins as the bag bursts open is kinda interesting. It also provides a new problem: how do you get your coins out of the dungeon now that the bag is ruined? It also provides some game balance so you don’t decide to go dual-wielding bags full of 300 coins. The warning could be taken as, “If you try to wield that as a weapon, the bag may break. Use a real weapon, unless you absolutely have to improvise.”

    Or the DM may have just liked having you have lots of broken weapons. 😉

    At any rate, the whole “world determined by physics” has been tried in numerous text MUDs. Almost none of them were ever released. The problem is that even if you can write a good simulation of physics, it makes world building that much harder. Sure, I can say the longsword is made of steel, but what are the physical properties of that steel? Was it high quality steel, or did it have too many impurities and imperfections? How do those factors affect teh brittleness of the steel? And, do those factors change if I use the sword in different ways, such as striking with the flat of the blade.

    Add on a graphical system on top of this and you have a mess. Despite the marketing hype, physics in single-player games is still lots of “good enough” simulation and frustrating gameplay.

    Feel free to prove us all wrong, though. Sometimes it’s good to have someone show up the conventional wisdom.

  2. Michael says:

    The answer to all your questions about the blade can be answered with a handful of equations. I like some of the points you have made though, especially about wanting to wield the weapon that deals out the max damage. I think you can get around this by either using a graphics system where the damage is shown rather than told through numbers, or you come up with a textural system such as “The sword sliced an artery” or “The strike delivered a surface wound.” I personally liked numbers, but I was swayed by the counter arguments of immersion and now I see their worth. That being said if you varied the creatures and people in the realm with different type of defenses then there would be no one true uber weapon. Someone wearing some sort of thick plate armor would be vulnerable to smashing weapons, while a slicing weapon would almost useless. This could be covered by the force per square inch formula of the weapon vs the hardness and absorptive properties of the plates. Now you can have an elephant step on the same plate creature and even with little momentum the pure pressure equation will immediately work. There will be times where pure physics will not be handy in very complicated situations, or for magic (unless you develop a physics of magic, something I would love to do) and those are the times you look stuff up. Otherwise there is a lot of this knowledge out there, and the computers now have the horsepower, why not turn them free. I’ll stop babbling now. :>)

  3. You missed my point. Admittedly, it was hidden in a lot of other words, but here it is again:

    “The problem is that even if you can write a good simulation of physics, it makes world building that much harder.”

    In M59, I define a new weapon by defining 5 values: damage type, magical damage type, quality type, weight, bulk. These values derive a few other values as well that affect gameplay. On the other hand, consider if I were to create a weapon in your proposed world using physics to define everything. I would need:

    * Material type (including specific things like impurities) for each part.
    * Physical dimensions (at least 3 in most cases) for each part.
    * Shape (sword blade vs. axe blade, etc.) for each part
    * Condition (sharp, dull, corroded) for each part
    * How all the parts fit together, relative to the weapon wielder.

    I could probably re-define all of Meridian 59‘s weapons before you could finish coding the description of even one weapon in your system. Now consider a game like WoW that has literally thousands of different weapons.

    At this point you might be tempted to take some shortcuts and standardize some elements. All swords are roughly the same size, right? We’ll assume people always stand about the same distance from each other in fights, so we don’t have to calculate different angular momentum for different locations on the blade being swung. We’ll standardize on a few material types. Keep going and you’ve circled back around to defining the four characteristics like I do in M59, but now you have a complicated physics-based backend that is only being fed limited information to keep things easy.

    This doesn’t even touch the technical issues you may have. In M59, a combat to-hit and damage are two equations with about a dozen different queries (weapon, armor, and player stats). Assuming you don’t take the shortcuts I described above, for a single swing in a physics-based combat system, you’ll need many more equations: angular momentum of the weapon, impact of the weapon against the target, effect on the target, the ability of the target to withstand the damage, etc. Now multiply this by thousands of people on a server and you start to have computation problems in an MMO.

    I meant what I said in my previous comment, though; don’t let me stand in your way if you’re absolutely convinced. It’s just that others have tried and nobody has yet been able to make this approach work right. Perhaps you have the mojo needed to make it work, though. If so, good luck. 🙂

  4. Michael says:

    I understand now. Yes you are right. No matter what you are going to have to take some short cuts. You are also right in the world building aspect. Creating weapons from scratch is sucky unless everything is based on a few templates. Maybe a blended approach would be a good medium. If you create a limited number of weapons (I know we said everything will be a weapon, but I can come back to that in a minute) that is your starting set in the world. Now you give the content users, the players, a tool to mold their own custom weapons. Here’s the catch, the weapons perform based on the physics of the weapon they make (and the smith’s skill, but that’s getting too specific). The more realistic or different with respect to physics, the more they can add and subtract from the amount of knowledge needed to create the physics behind the blade. There would have to be a bare minimum (sort of like the table of stats you referred to for the weapons you develop in your system), but since we are using the user’s PC to do all the fancy calculations then I can receive a fully formed object to look at and decide if we want to release it into the wild. That’s just the start since now the person who gets said weapon will have to train with it to learn it’s balance and maybe change their fighting style because of it. It would give a lot to experimenting which as a player I would love. Is this a perfect solution, no and your solution with tables is still faster to implement and supplement from a single source perspective. I think the approach outlined here is more of an evolutionary step than a revolutionary one.

    As for objects being weapons. Here is the worst assumption of all. Unless otherwise stated all objects inflict blunt damage and use the calculated moment of inertia around the most logical (as determined by the object’s creator) place to grab said object.

    I hope this works. It may be as you said a fools errand (paraphrasing. You gave it much more respect, but I understand the undertaking could very well be a boondoggle) , but every year people get closer and closer to a truer alternate reality (whatever that really means) and maybe we hit it at the right time. I can hope it will be the better mouse trap, but only time and hard work will tell. Thank you for your comments. It gives us something to reality check against. 🙂

  5. Dave says:

    As a hobbyist whose focus is small worlds, I have the luxury of not caring about scaling for a large MMO and I have the luxury of not having to have a shipping game on such and such a date that can pay back the investors plus profit by such and such a date. So I can act like a bright eyed, bushy tailed kid.

    Let’s take the example of defining a weapon. What are the critical elements? If it is a western style sword, it will have a pommel, grip, tang (sometimes the tang is called hilt, sometimes the tang+grip is the hilt) and blade. It will be made of something and that material will have various properties, the most important of which will be hardness and density. If you are using a 3D engine, you can run a script on your models to approximate the moment of inertia, presuming that it is held at the handle. If it is a text MUD, that would be a back of the envelope calculation or possibly a hand waving number.

    That’s it.

    Damage is about converting kinetic energy to heat. That kinetic energy will be translational (i.e., based on how fast the object was moving when it hit) and rotational. The latter can be pre-calculated. If you have various swing styles, you can create kinetic energy profiles and then just plug in things like character strength, skill, weapon mass and moment of inertia.

    I do think that it is doable. At the end of the day, I think it will add simplicity for the designer. The trick is knowing when to approximate the horse as a sphere.

  6. Pingback: The Deep Physics – Intro « Dancing Elephants

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