GURPS Scale and SM (spinoff from +1/-1 to hit)

[Anthony]

A concept which has appealed to me for a while is a scale setting switch or advantage. The core concept is that in a Scale X game, you can just build PCs as normal SM +0 characters, and then the game's scale will take care of making them interact properly with the environment. The general likely components of scale are:

• Damage: multiplies damage/divides damage taken. Affects DR, HP, etc.
• Hexes: adjusts the definition of a hex. Multiplies ranges, areas, etc.
• Turn Length: multiplies how long a turn takes.
• SM: adjusts the zero point for SM. Often the same as hex scaling.
• Weights: multiplies weight lifted or affected.

A fairly consistent scaling for giants (which makes things like falling and collisions work correctly) is

• Pick a base SM (say, +10 for a Kaiju game with 200-300' tall monsters)
• Damage scale is 1.5x SM (in our Kaiju game, +15 means 300:1)
• Hex Scale is equal to SM (in our Kaiju game, +10 means 50 yard hexes)
• Turn Length is equal to SM/2 (in our Kaiju game, +5 means 1 turn is 7 seconds). This means a Move 5 Kaiju is moving 250 yards in 7 seconds, or about 70 mph.
• SM is (obviously) equal so SM (our Kaiju have a +0 modifier to hit other Kaiju... but -10 to hit a single human, unless we use our body parts as area attacks)
• Weight is generally 3xSM (so +30... multiply weights by 100,000, so BL 20 becomes BL 2 million or 1,000 tons).

The trick is converting creatures from one scale to another. In general:

• Damage: for attacks below 1d, +1 scale is +1 damage. Once 1d is reached, multiply by the scale ratio (so 1.5x, 2x, 3x, etc). Do this in reverse for reduced scale. Thus, if our Kaiju is doing a basic punch for 1d-2, but we're operating in human scale, 2 levels of scale get that up to 1d, then the remaining 13 levels of scale get it up to 150d. In the reverse direction, a LAW doing 35d(10) gets reduced to 1d by 9 levels of scale, then to 1d-6 for another 6 levels scale.
• Hex: a creature operating on a larger hex scale has (+relative scale) to hit, but this bonus cannot more than negate modifiers for range (this combines with the SM rule, see below); a creature operating on a smaller scale has (-relative scale) but can compensate by getting closer. Area effects are multiplied as normal. (kaiju example deferred).
• Turn Length: treat as altered time rate (so our Kaiju have ATR(1/7)).
• SM: a creature with a higher SM scale has a penalty to attack and perception equal to the SM difference. The combination of SM and Hex may cancel out, turning into a minimum range penalty (our Kaiju have a -10 to hit a SM 0 target, but they stay at a -10 penalty out to 100 yards). Note that it may be more realistic to do this based on the SM of the target (so attacking a SM +10 target has a +10 modifier, but that modifier is only applicable to negating range penalties).
• Weights: if using KYOS, add (10/6) weight scaling to contests of ST (so our Kaiju, with weight scaling +30, have +50 to grapple/etc).

It's possible to use a log scale other than standard GURPS SM (+6 per x10). If you're doing that, you'll probably want to convert to a linear scale before figuring out effects on attack rolls.

Point value... aii. Off hand:

• A level of damage scaling is probably worth some between [50] and [100]. I have an attachment to [500] for D-scale, so [500/6].
• A level of hex scaling gives +1 to negate range modifiers, but also increases area effects (at least [10]).
• A level of turn length scaling, based on ATR, is probably about [-50]
• A level of SM gives a general-purpose -1 to most DX and Per rolls, probably [-20].
• A level of mass scaling is 1.67 lifting ST in KYOS ([35/3]).

A useful combined scale is

• +3 Damage scale [250]
• +2 Hex scale [20+]
• +1 Turn scale [-50]
• +2 SM scale [-40]
• +6 mass scale [70]

Total value is 250; our Kaiju have 5 levels of this for [1250].

Note that the above is cinematic giant scale, which ignores the square/cube law. A pure square/cube formulation is instead

• +1 damage scale [83]
• +1 hex scale [10]
• +1 turn scale [-50]
• +1 SM scale [-20]
• +2 mass scale [23]

Total value is 46. Realistic animals actually scale somewhere between these two, for a package more like

• +5 damage scale [417]
• +4 hex scale [40]
• +3 turn scale [-150]
• +4 SM scale [-80]
• +10 mass scale [117]

Total 343 for 4 levels SM. Note, however, if you're not using cinematic giant scale, things like collisions and falls start behaving differently.

[Pursuivant]

This is a potentially elegant approach.

In the past T-Bone has put a lot of thought into alternate GURPS Scales with his GULLIVER rules for GURPS 3E. It also dig into the mechanics of mass vs. SM mostly by riffing off of the old GURPS 3E Bunnies & Burrows rules.

One of my house rules is that hits that do 0 HP or less still inflict 1 HP of damage on creatures at least one Size smaller than the attack scale itself. That means that regardless of the damage roll, a human always inflicts enough HP with a weapon attack to kill a tiny creature like a mouse or insect. It gets rid of silliness like a ST 8 human not being able to reliably kill a fly with a single punch.

[pawsplay]

Originally Posted by Pursuivant

This is a potentially elegant approach.

In the past T-Bone has put a lot of thought into alternate GURPS Scales with his GULLIVER rules for GURPS 3E. It also dig into the mechanics of mass vs. SM mostly by riffing off of the old GURPS 3E Bunnies & Burrows rules.

One of my house rules is that hits that do 0 HP or less still inflict 1 HP of damage on creatures at least one Size smaller than the attack scale itself. That means that regardless of the damage roll, a human always inflicts enough HP with a weapon attack to kill a tiny creature like a mouse or insect. It gets rid of silliness like a ST 8 human not being able to reliably kill a fly with a single punch.

So does a cockroach have 2 hit points? I've seen those take a hit or two...

[Anthony]

Originally Posted by Pursuivant

One of my house rules is that hits that do 0 HP or less still inflict 1 HP of damage on creatures at least one Size smaller than the attack scale itself. That means that regardless of the damage roll, a human always inflicts enough HP with a weapon attack to kill a tiny creature like a mouse or insect. It gets rid of silliness like a ST 8 human not being able to reliably kill a fly with a single punch.

Well, by these rules a SM -15 fly probably has a damage scale between -15 and -22, and a 1d-4 punch scales up to at least 70d fly-scale.

Btw, added some edits on how less cinematic scaling works.

[Pursuivant]

Originally Posted by pawsplay

So does a cockroach have 2 hit points? I've seen those take a hit or two...

Remember that GURPS assumes that people reduced to HP x -5 die instantly, rather than dying slowly and messily like they do in real life (e.g., agonal breathing and instinctive neurological reactions after an untreatable, soon-to-be-fatal head injury).

Unless a cockroach can still go about it's normal business rather than just scuttling off to die one human-sized stomp equals one cockroach-sized funeral.

[Pursuivant]

Originally Posted by Anthony

Btw, added some edits on how less cinematic scaling works.

It occurs to me that GURPS Spaceships might be a starting/comparison point for scaling large objects simply, since each +1 to SM works out to approximately a 3x increase in volume. How dDR scaling for armor works and the way that HP are calculated might be useful, if only as a comparison of your system to RAW.

[Anthony]

Originally Posted by Pursuivant

It occurs to me that GURPS Spaceships might be a starting/comparison point for scaling large objects simply, since each +1 to SM works out to approximately a 3x increase in volume. How dDR scaling for armor works and the way that HP are calculated might be useful, if only as a comparison of your system to RAW.

GURPS Spaceships is just pure square/cube scaling (other than not using turn scaling)

[Culture20]

Originally Posted by Pursuivant

This is a potentially elegant approach.

In the past T-Bone has put a lot of thought into alternate GURPS Scales with his GULLIVER rules for GURPS 3E. It also dig into the mechanics of mass vs. SM mostly by riffing off of the old GURPS 3E Bunnies & Burrows rules.

One of my house rules is that hits that do 0 HP or less still inflict 1 HP of damage on creatures at least one Size smaller than the attack scale itself. That means that regardless of the damage roll, a human always inflicts enough HP with a weapon attack to kill a tiny creature like a mouse or insect. It gets rid of silliness like a ST 8 human not being able to reliably kill a fly with a single punch.

The reverse (allowing reduction to zero for cutting/impaling if the target is larger) could also help with the housecat versus peasant problem, but it does feel like giving away free DR at human/slightly taller human scale.

[Anthony]

Originally Posted by Culture20

The reverse (allowing reduction to zero for cutting/impaling if the target is larger) could also help with the housecat versus peasant problem, but it does feel like giving away free DR at human/slightly taller human scale.

Human skin definitely has non-zero protective value, though its true DR might be fractional.

[Varyon]

Originally Posted by Pursuivant

It gets rid of silliness like a ST 8 human not being able to reliably kill a fly with a single punch.

I mean, an ST 8 human typically won't kill a fly with a punch unless there's something to prevent the fly from being knocked back, but that's a bit difficult to work out for an RPG.

Originally Posted by Anthony

Human skin definitely has non-zero protective value, though its true DR might be fractional.

I often assume 0.5 DR for human skin. This probably overstates the effect but it gives a jumping-off point at least. The "minimum 1 point" rule for cutting and impaling is a resolution issue; it largely goes away if you replace GURPS' linear HP with something logarithmic. Which I think would work well here - something that is SM +2 and average Strength for its size could basically be run as having ST 10 but have incoming damage at -2 steps and cause damage at +2 steps.