Experiment: Arma Obscura – Weapons Defined as Nomograms

Going Analog

Some time ago I started checking for alternate methods for analog devices to keep track of damage on traditional RPGs and I still don’t know why, I ended up with this way of defining weapons.

From Slide Rules to Nomograms

First, I found out about the slide rules thanks to the weird fascination that the guys at Numberphile have for these devices and digging a bit more it took me to know about their 2D relative: the slide charts, which have been used for the most varied purposes, from pregnancy week counters to horoscopes.

Numberphile videos about The slide rules:
· The iPhone of Slide Rules
· The Electric Slide Rule
· The Slide Rule

I fell in love with the these simple mechanical artifacts and one thing lead to another until I found out about the arcane piece that are Nomograms.

A Smith Chart.

Nomograms will allow you to have an aproximated output of complex calculations by just tracing a line on a chart. Probably the most geometrically beautiful of all is the Smith Chart for calculating impedances in electronics. I have to admit that I wouldn’t be able to use it nor understand it, yet with barely any decent knowledge of mathematics and in an(other) act of blind stubbornness I decided that these complex pieces of cardboard engineering would be awesome for a game, not to just keep track of simple counters or for calculating damages with modifiers, but to create an -almost- deterministic system of weapons for a game like a RPG or a Tabletop Dungeon Crawler. In this Weapon-as-a-Nomogram system almost all decisions are in the hands of the player and it would allow to be more simulationist (stats, params and modifiers) without the gameplay overhead of having to check several tables and ‘compute’ the outcome. Instead, the GD does the job and the player just traces a line.

First attempts

My barely usable division nomogram.

In fact, I wasn’t aware but it seems that Nomograms have been used in war-games for a long time as it can be seen in this wonderful article in ProjectRho and all of its bibliography. I read this and the Dead Reckonings articles about the matter and well… I didn’t understand much about how to do complex stuff. I manage to create my own version of some basic operations such as addition, subtraction or division, but from moment zero I was aware that I would rather brute-force the hell out of it rather than learning to create any polynomial function or work on non-linear or curved coordinates and stuff like that, because I don’t even know what I am saying. Also, I’m afraid of the hounds of Tindalos.

The mighty bow of brute force

So my first attempt on Weapons Defined as Nomograms was a chart for a bow which had some few contradictions here and there and was totally generic in stats and theme. Current prototype is heavily based on it, though.

If you are wondering which math function I used to map it the nomogram, it is called “designer’s brain mal-function” and it consists in moving lines around until everything makes some sense before bothering a friend that actually knows some maths.

The inputs would be:

  • POWER: the power that the player decides to use, capped by any of his stats (dexterity, for instance)
  • DISTANCE: determined by the context of the game. I decided to cap the maximum distance as a parameter of the weapon and also to set a minimum distance above the point-blank shot, beacause it didn’t fit well with an arrow and also created an interesting gap in the outputs.

The oupouts would be Accuracy and Damage which are mapped in opposite directions so it generates a trade between both:

  • ACCURACY: this would be mapped to a dice roll, I assumed that a d100 would work naturally as a way to express a chance of hitting the target.
  • DAMAGE: it would be the damage (later translated from percentage to actual Hit Points).

The device showed a property that I liked a lot. It offered the player 2 spaces of action, one focused on accuracy and the other, on damage. Within those continuum 2 spaces of action and given the distance, the player decides if he wants to trade damage for accuracy or the opposite and in which degree. It is the player that decides how much luck he wants to push in exchange of damage or how much damage he wants to potentially inflict in trade for its chances.

Distance was represented as a circle and lines needed to be traced tangentially to it. This fact multiplies the amount of unavailable Damage-Accuracy choices, making the player choices more extreme. In this way, shooting from a longer distance implies having to take more radical Damage-Accuracy choices.

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