Add damage reduction component

[NikkoJT]

GM dramatically increases our chances of playing missions with high-calibre weapons and zero body armour.

As a result, we should implement a component that can reduce incoming damage to players, most likely by event handler. This will allow us to survive more than one shot and have more fun. This component may also be useful in vanilla missions.

Requirements:

• Affects all incoming damage types on players
• Optional, either by mission-internal parameter or host parameter, or both
• Not interfered with by Safe Start
• Consider impact on vehicle damage
• Don't affect damage to AI (possibly a parameter to do so)
• Probably around a 40% reduction in damage but needs evaluating

[shadow-fa]

code snippet for later (so I don't forget):

_x addEventHandler ["HandleDamage",{
    params ["_unit", "_hitSelection", "_damage", "", "_projectile", "", "", ""];
    private _oldDamage = _unit getHit _hitSelection;
    (_oldDamage + ((_damage - _oldDamage) * 0.60))
}];

[darkChozo]

Not totally tested code snippet for making vehicles unblowupable. Note the !isNull driver _unit; should probably be count crew _unit == 0 for general use, or just removed entirely.

_x addEventHandler ["HandleDamage",{
	params ["_unit", "_selection", "_damage", "_source", "_projectile", "_hitIndex", "_instigator", "_hitPoint"];
	_od = _damage;
	if (alive _unit && !isNull driver _unit) then {
		if (_hitPoint == "") then {
			if (_damage > .7) then {
				_damage = .7;
			};
		};
		if (toLower _hitPoint in ["hithull"]) then {
			if (_damage > .7) then {
				_damage = .7;
			};
		};
	};
	_damage
}];

EDIT: turns out i'm dumb and the original event handler didn't work properly, this one is a bit more up to date.

[darkChozo]

Attempt at a properly scaled damage event handler:

this addEventHandler ["HandleDamage",{
  params ["_unit", "_selection", "_damage", "_source", "_projectile", "_hitIndex", "_instigator", "_hitPoint"];

  _currentDamage = damage _unit;
  if (_selection != "") then {
	_currentDamage = _unit getHit _selection;
  };
  _hitSize = _damage - _currentDamage;
  _newDamage = _damage;
  if (_hitSize > 0) then {
	_newDamage = _currentDamage + (.2 * (_hitSize ^ .4));
  };
  
  systemChat format ["%1 | %2 | %3 | %4",_selection,_currentDamage,_damage,_newDamage];
  _newDamage
}];

Probably needs tweaking but works reasonable well on AI. If I had to guess it probably reduces damage too much, but it does do a good job at scaling down heavy hitters like .50 cals while also keeping small stuff like 9mm useful.

[shadow-fa]

Is there a good reason for the non-linear scaling? I experimented with a few values and found that's it's pretty hard to get the exponent right, so that it doesn't end up increasing the damage if the incoming damage is small. I think linear scaling makes more sense and is easier for missionmakers to understand and tweak.

[darkChozo]

I came up with the formula by doing a regression of experimental damage values against how much I thought the weapon should do (basically 5.45 is a three hit kill, 7.62x51 is a two hit, .50 just barely doesn't kill you). That relationship ended up being nonlinear; basically a .50 cal round or even a 7.62 round does so much more damage than 9mm that if you reduce damage linearly so 7.62 is capable of wounding, 9mm becomes so plinky that it takes 10-15+ rounds to kill.

That being said, I'm doing some testing now and I'm not sure that my experimental numbers were all that accurate (they're kind of hard to measure). However, playing around with a linear reduction handler, I'm running into another issue; it creates a huge disparity between killing by hitpoint damage and killing by overall damage. Basically, using a linear damage handler with a 1/18 multiplier, you get pretty reasonable results when shooting one hit point, but shooting multiple hitpoints significantly increases shots to kill.

https://www.youtube.com/watch?v=xojq6suAn_Y

I think the nonlinear handler inadvertently helps with this issue by reducing the usually-higher hit point damage by more than the usually-lower overall damage, bringing them closer together. But all this definitely needs testing since it's mostly feel-based.

It's also worth noting that the nonlinear handler seems to work well even with armored targets. I've tested this even less but I suspect a linear handler would make body armor wayyyy too effective.

Regarding the exponent, I don't think there's a simple function that has the shape we'd want and also doesn't increase low damage amounts. In practice I don't think it matters; it only increases very small amounts and not by much.

I also don't think that this is something that should be user-tweakable, since it's very dependent on the particulars of Arma's damage system. We could offer several options for different levels of damage reduction, though.

[darkChozo]

Current state of the damage handler: https://pastebin.com/58ytEu1E

I think this should receive a few enhancements before being properly integrated into F3. These are:

1. Add in a headshot damage multiplier. In vanilla AFAIK the only benefit to headshots is that the head is usually poorly armored, but with the damage handler it feels a bit weird to tank a bunch of shots to the face.
2. Investigate low-end damage. 9mm feels a bit too plinky IMO, it may be prudent to make it a liiitle more impactful.
3. Add in options for the level of damage reduction. My thought would be to have a lite/lower reduction option, a higher reduction option, and a tank-like/superhuman option for silly scenarios.
4. Add in a parameter for damage handling. The reasoning here is twofold; first off it can be used to make missions easier for lower player counts. Second, if BI changes revive and breaks it in the future, this would allow us to turn it off of it's a problem.
5. Modify the script to take in units as arguments, similar to assignGear_AI/setSkill. The use case here is if you want to make AI more durable for whatever reason. This should also allow you to specify the level of reduction as an argument, the superhuman reduction being particularly relevant.