PDA

View Full Version : Unified Game Mechanism for Force?

FreakyCheeseMan
2013-02-13, 03:17 PM
So, I'm in the process of putting together a rule system to go with my world building project, Planets of Magic (http://www.giantitp.com/forums/showthread.php?t=271255).

I'm trying to keep the rule system as realistic as I can, without over-complicating things or slowing down game play. As part of this, I think I want to come up with a unified game mechanism for dealing with Force. As a lot of combat takes place aboard open-air spaceships, getting thrown off into the void of space is probably going to be a big thing; plus, there's an entire school of magic focused on raw kinetic force, martial classes trying to push each other around, etc.

So, what I want to do is come up with a basic system of force that could cover everything from strength checks to open a door, fighters pushing each other back and forth, mages creating artificial gravitational fields to keep fighters away from them, maybe some stuff with lightning bolts or like charges knocking people back...

I figure I'll need a quick notion of instantaneous force (force spell hits you, boulder slams into you), as well as force-over-time (Gravity, maybe strong wind effects). Right now, I'm figuring I'm going to use an earth-like gravity as the basic unit of force, but past that, it's all open.

Has anyone seen a system like this? Am I insane to attempt to incorporate it into my game? It seems like D&D has a lot of the same stuff, but it's always on an effect-by-effect basis (Strong winds, bull rushes, etc).

Jormengand
2013-02-13, 03:20 PM
I've seen a system which does this, but it's literally just adding and subtracting forces to see how far you move. It also involves a lot of calculating moments and working out what the gravitational constant of [insert planet here] is.

FreakyCheeseMan
2013-02-13, 03:36 PM
I've seen a system which does this, but it's literally just adding and subtracting forces to see how far you move. It also involves a lot of calculating moments and working out what the gravitational constant of [insert planet here] is.

Hrrm.

I was thinking that, while downward force would be there, so long as it was 1G, it would never be referenced. Higher Gs might impose movement penalties or strength checks to move at all. 0G would... well, 0G would be kinda weird, but hopefully rare, and most characters would either have flight or some way to cling to walls/floors. There might also be something about upward force, but I doubt it'd be worth the trouble.

Not sure how I'd handle flying- that might be worth working out in terms of pure forces, especially as "Flight" spells come from the "Force" school.

Mostly, I wanted a system for forced pushing parallel to the ground, to answer questions like:

"There is X units of lateral force acting constantly against you; what happens? (Slowed to a crawl, pushed back, knocked over, etc)"

"There is a sudden X force applied to you unexpectedly; what happens? (Knocked over, pushed back, thrown against the far wall for some units of damage)"

"There is an object that is moving/needs to move. How many units of force does it take to move it, and how many can each character generate?"

Oh, and maybe "X units of force are applied to your weapon - are you disarmed?" or "X units of force are continuously applied to your weapon, away from the target - Can you hit them?"

Grod_The_Giant
2013-02-13, 04:36 PM
Might be worth taking a look at the kinds of things you can do with this (http://www.d20herosrd.com/6-powers/effects/effect-descriptions/move-object-control). Basically, it treats telekinesis as ranged strength. So, everything you can do in arm's reach, you can do at a range. The benefit of treating strength and force magic as roughly the same thing is that you get a unified set of mechanics. Knocking someone back? Bull rush. Forcing someone to the ground? Trip. And so on-- basically, you'd either be rolling Force Magic against Force Magic or Force Magic against Strength.

FreakyCheeseMan
2013-02-13, 04:39 PM
I like that. My system is nothing like D&D - it isn't even a D20 - but I could see that having potential.

...I got the sudden mental image of a group of riot-cop mages clearing an angry mob out of a street with gravitational forces, or one officer using force magic to hold a group of perpetrators against a wall while his partner frisks them down. I like these images.

BarroomBard
2013-02-14, 01:17 AM
Well, let's look at it independent from your system.

F = M x a

Which also means

a = M/F

Which means that if you hit an object with mass M (which would essentially be a stat in your system which is affected by Gravity) with a Force F, you divide the two and get an acceleration value, or how the object is affected.

Essentially, if you make Mass into a stat in your game, you can use it as a kind of armor against Force effects. I hit you with a telekinetic push, and it knocks you back based on how strong my push is and how heavy you are. In a tug-of-war situation, you subtract the opposing forces from each other, and apply the Net Force as the Acceleration, in whatever direction wins.

FreakyCheeseMan
2013-02-14, 01:25 AM
Well, let's look at it independent from your system.

F = M x a

Which also means

a = M/F

Which means that if you hit an object with mass M (which would essentially be a stat in your system which is affected by Gravity) with a Force F, you divide the two and get an acceleration value, or how the object is affected.

Essentially, if you make Mass into a stat in your game, you can use it as a kind of armor against Force effects. I hit you with a telekinetic push, and it knocks you back based on how strong my push is and how heavy you are. In a tug-of-war situation, you subtract the opposing forces from each other, and apply the Net Force as the Acceleration, in whatever direction wins.

I doubt I'll go so far as to have mass be a stat, beyond just size category- though, I suppose I might have some creatures/objects have a tag that says, for the issue of force effects, they count as a category higher or lower.

Acceleration is kinda a problem, cause acceleration means momentum, which is just confusing in a turn-based game; mostly, I figure that a force effect will just push a character back a number of squares, and possibly deal damage if it drives them into an object.

BarroomBard
2013-02-14, 01:56 AM
Well, acceleration is just distance over time, essentially.

In a more abstract/let's-make-real-physicists-cry way of looking at it: every exertion of Force - spells, winds, punches, falling, etc. - has a number. This number is, more or less, the Force involved.

This number is manipulated somehow by the object the Force is acting on. The result is how far the object may be moved in one turn.

Generally, you wouldn't have to think of rules for causing something to go flying for several turns, unless a very large amount of force was involved, or the local gravity is quite a bit under Earth standard.

FreakyCheeseMan
2013-02-14, 02:48 AM
Well, acceleration is just distance over time, essentially.

In a more abstract/let's-make-real-physicists-cry way of looking at it: every exertion of Force - spells, winds, punches, falling, etc. - has a number. This number is, more or less, the Force involved.

This number is manipulated somehow by the object the Force is acting on. The result is how far the object may be moved in one turn.

Generally, you wouldn't have to think of rules for causing something to go flying for several turns, unless a very large amount of force was involved, or the local gravity is quite a bit under Earth standard.

Acceleration is distance over time, which is why I didn't want to deal with it. But, yeah, as a basic system, it's gonna be something like you describe. There are still questions, though. How do I deal with immediate vs sustained force? Upward and downward force? Damage from slamming into a wall vs. skidding along the floor? Force on flying targets? A person trying to push forward against a force? A person trying to move with the force at their back?

BarroomBard
2013-02-14, 12:46 PM
For damage from hitting something: you say that a Force of X does Y damage (A punch of Force 1 does 1d4 damage or something). If you hit a solid object, you take damage as if from a Force moving your "acceleration". If that's enough to destroy the wall, you keep going, at diminished force.

FreakyCheeseMan
2013-02-14, 12:50 PM
For damage from hitting something: you say that a Force of X does Y damage (A punch of Force 1 does 1d4 damage or something). If you hit a solid object, you take damage as if from a Force moving your "acceleration". If that's enough to destroy the wall, you keep going, at diminished force.

Well, I'm using a wound system, so I need to figure out what body parts get hit. Also, I'm ulikely to say that the force itself does damage, unless maybe there's an extra strong (I'd say at least 4 or 5 g) force holding you against an object. The rest of the time, you're just getting jerked around.

Plus, the way my schools are currently divided, Force mages have a lot going for them - battlefield control, defenses and utility. Their spells are harder to cast to compensate, but still, I want to keep their offense a bit limited.

sreservoir
2013-02-14, 05:14 PM
acceleration is rate of change of rate of change of distance with respect to time. if you push a thing, it will keep going until something else does forces on it. feh, physics.

FreakyCheeseMan
2013-02-14, 08:35 PM
acceleration is rate of change of rate of change of distance with respect to time. if you push a thing, it will keep going until something else does forces on it. feh, physics.

Well, yeah. But, game systems are an abstraction, so when you push something along a floor, you need a quick abstract system to see how far it goes.

Plus, unless it's actually in space, you probably don't want to have multi-turn slides. That would just be annoying.