Toughness

Below is a revised Toughness trait for GURPS that represents resilience from thick muscles. It’s as good as DR against crushing damage, letting a hero laugh off weak punches. Yet Toughness isn’t DR; a weak knife slash will still cut you, and a stab to the heart can kill.
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The rule:

Purchase Toughness in levels, like DR. (See Cost of Toughness below.)

Toughness absorbs impact, and so protects only from crushing, cutting, impaling, and piercing damage types. It doesn’t protect against hazards like poison, disease, acid, or fire. (When in doubt as to whether an attack causes damage due to impact or not, make a GM call or use half Toughness, rounding down.)

For impacts, follow standard GURPS procedures for handling damage: Subtract DR, and multiply the remaining basic hits for damage type and location.

Now reduce final damage by the smaller of your Toughness or the impact’s basic hits (after DR). The effect: Toughness subtracts from only the basic “impact” hits of the blow, and not the extra hits from edges, location, or other multipliers.

Examples:

Example: You have Toughness 3. That lets you shrug off up to 3 points of punch or other blunt damage. A punch for 5 points of damage inflicts only 2 points on you.

But a 2-point edged attack will still cut you. It deals 2 points of basic impact plus an extra point of damage from cutting. Toughness absorbs the 2 points; you take the extra 1 point as damage.

Next you take a 5-point stab to the vitals, which is tripled to 15 damage. Your Toughness subtracts only 3 hits from those initial 5 basic hits. You take 2 points of those basic hits, plus all 10 extra points from the stab, or 12 damage total.

Next it’s a 4-point crushing blow to the neck. Multiply by 1.5 for target location, to get 6 points of damage. Toughness subtracts 3 points; you take 3.

You now don DR 1 armor, and take a 5-point punch to the torso. DR subtracts 1 point of damage, then Toughness absorbs 3; you take only 1 point.

Next comes another 5-point stab to the vitals. DR subtracts 1 from basic hits, leaving 4. Multiply these by 3 for vitals: 12 damage. Your Toughness absorbs only 3 of the 4 basic hits; 1 basic hit gets through, as do all 8 hits of the extra impaling damage. You take 9 damage.

Setting Toughness:

An appropriate default level of Toughness for any creature is ST/5, rounded down.

The upper limit is up to the GM; twice the default level is reasonable. Unnatural or alien flesh may allow higher levels (or even require it as part of the racial template).

The eyes have no Toughness.

The skull has DR instead of Toughness – essentially, its Toughness is converted to DR. (You might want to set brain DR to ST/5, the same level as suggested Toughness.)

Cost of Toughness:

Toughness is less useful than DR. Treat it as a -40% limitation on DR, or 3 points per level.

Toughness essentially replaces the Tough Skin and Flexible limitations on DR (BS 47). It (and Edge Protection) act as alternate ways of handling similar effects.
Variants and options
Balancing Toughness and damage

Toughness makes it a bit harder for characters to hurt each other. That’s not a big problem in play. Those characters have paid points for the defense, and it’s notably inferior to DR: no matter how much Toughness you sport, a stab in the right place will leave you dead.

But with many characters stocking up on this new form of defense, you’ll want to consider combat balance. If you want to boost overall combat damage a bit to compensate for common Toughness, here are suggestions:

Encourage more strong AOA attacks, bone-crushing techniques, and bigger weapons. Also remind players that ST is more important than ever for breaking Toughness-enhanced foes!
Use Toughness together with increased ST-based damage (see New Damage for ST below and the linked article New Damage for ST).
See other suggestions in the above article for boosting damage, under Expanded Damage Table.
See the options immediately below that reduce Toughness for some damage types and locations.

Toughness and damage types:

Impaling or piercing damage with a multiplier of x1 (impaling to a limb, piercing, etc.) or x0.5 (small piercing) can interact oddly with Toughness (among other rules). This is an artifact of the strange ruling that these flesh-penetrating attacks cause damage equivalent to or less than non-penetrating blunt attacks.

To address this, halve Toughness versus small piercing attacks; this can be explained as exceptional penetration versus muscle. It helps prevent Toughness from erasing the attacks’ small final damage.

Example: You have Toughness 3. You’re hit by a small-caliber bullet which, after DR, inflicts 6 basic hits. Damage is halved to 3 for small piercing. Now Toughness kicks in, but only half your normal amount, rounded down to 1. It absorbs 1 point of the damage; you take 2 points.

For impaling or piercing attacks with a x1 multiplier, you could proceed as usual, subtracting Toughness from final damage (which will be the same as basic hits). That makes Toughness as useful as DR versus these attacks. But if that seems unrealistic, halve Toughness as above. This provides some wounding benefit over blunt attacks.

Toughness and location:

For more detail, modify Toughness as follows (at least for humanoids):

Halve Toughness (round up) in the hands, feet, groin, and nose. There’s less flesh and muscle there to protect delicate stuff. (The throat would qualify too; treat as the neck with an extra -2 TH, or -7 TH total.)

Conversely, give Toughness a 50% bonus (round down) against torso attacks from the rear, thanks to big back and buttock muscles. (Drop that bonus for targeted attacks to the kidneys, spine, etc.) The same could apply to the upper chest, upper arms, and upper legs, if the attack were specified to hit those locations.

That extra Toughness is why a boxer unable to dodge blows will at least try to catch them on sturdier locations. (It’s also why you’d curl up and expose your back to passively take a rain of blows. It’s better than being kicked in the front… a little, anyway.)
Toughness and shock

The default way to handle shock from blows is also the easiest: Compute shock as final damage times any appropriate multiple (such as doubled vs the groin). If Toughness absorbs all damage, then there’s no shock.

Another option is to calculate shock from damage before Toughness, and then subtract Toughness from shock. That’s a little more complex, but allows high-shock attacks (hello again, groin!) to inflict shock even when Toughness shrugs off actual injury.
Free Toughness

As Toughness is an optional purchase, you can design oddities such as the PC with all the bar-bending muscles and Hit Points of his ST 20, but who chooses to buy none of the expected Toughness to go with it. Or build small, wiry (even rubbery) PC who laughs off kicks and punches with unusual Toughness.

Alternately, the GM could include Toughness as a free, innate component of ST. Under this option, Toughness equal to ST/5 (rounded down) is automatic for all creatures, at no cost. Additional Toughness is still available, as above. (Or, if by chance you use some alternate scheme for ST (like this), set the cost of added Toughness to 30% the cost of added ST.)

This option offers a nice consistency in character abilities: Any creature of a certain strength will be certain to sport an appropriate and generally predictable resistance to impacts. But it also adds benefit to ST for no extra cost, so use it with caution. (Be sure to also consider the issues discussed under Balancing Toughness and damage.)

Required Toughness:

As a middle ground between optional purchase of Toughness and the above built-in Toughness, you can charge the suggested point cost for any and all Toughness (no freebies!), and require that all characters purchase the suggested level (or higher). That too offers consistency in character design, though it also tells players where to direct some of their character points.
When to use it

Toughness is a tool for those GMs who want a little extra combat detail. Using it consistently across characters and creatures adds a very realistic element. At the same time, hefty levels of Toughness are a fantastic way to build cinematic heroes that shrug off all sorts of bone-cracking blows, without the invulnerability of DR.

Toughness in an action hero has effects different from extra Hit Points. A few points of the latter will let the hero take an extra blow or two, but that’s it; until he’s healed up again, he can’t take any more blows than if he hadn’t bought those extra Hit Points. A couple extra points of Toughness, however, may let him take dozens more mook-level punches than he could have taken otherwise. Then again, it won’t avail him much against a bullet.

Toughness

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