Homebrew rule: damage threshold mechanic

[knightofrubus]

For posterity as this was already up in the FB group. This is a tweak to the game to use a Threshold mechanic for damage. It still uses most the combat rules as is but might need some minor tweaks to make it work 'right'.

Comment and critique are welcomed!

https://docs.google.com/document/d/1odOuPzMnaeZVhfVn608KNyqTxB9pekF6LB3OT0UsFlQ/edit?usp=drivesdk

[mmartin798]

Just a couple of initial observations before I start digging deeper into this. First, the rules are quite clear for ballistic damage. How does this system deal with whole body damage from explosives, electrocution, collision/fall damage, etc? The second is how are you handling SP/BP recovery? Are you using the existing rules or something else?

In the meantime, I will just take a character and shoot at it a few times to see how it differs.

[knightofrubus]

I'll start digging into those next. I've got an inkling how Fire will work electrocution and falling not so much that will take a bit longer most likely. I might also tweak a few other things as I go.

[mmartin798]

My preliminary results are in and the results are a little mixed. This could be in part because I was a little unsure how to apply burst fire, so I did it resolving individual hits and using a single total for damage from the burst. I will summarize the 9 test cases. In all cases, the target had CON 20, FOC19. That gave the target, using the new rules, Threshold of 20, SP 20 and BP 20. The target was assumed to be wearing resistweave coveralls. The shooter was using an M4 at 200m with a Rifle skill of 74%. For comparison purposes, half the DoS was used to increase damage for the 4e rules results. Failed shock rolls for 4e will also be indicated.

Test set 1 - Single round

1) DoS 1
Hit location: Right Thigh
4e Rules
Failed shock roll
8 SP, 13 BP

New Rules
No damage

2) DoS 5
Hit location: Right Upper Torso
4e Rules
10 SP, 13 BP

New Rules
1 SP, 1 BP

3) DoS 4
Hit location: Left Upper Arm
4e Rules
9 SP, 9 BP (Exceeds SP of location rendering arm unusable)

New Rules
1 SP, 1 BP

4) DoS 12 (Exceptional success)
Hit location: Right Calf
4e Rules
Failed shock roll
13 SP, 13 BP
Limb dismembered
Critical Bleed

New Rules
Dead

5) DoS 4
Hit location: Abdomen
4e Rules
9 SP, 9 BP

New Rules
1 SP, 1 BP

Test Set 2 - 3 round burst

1) DoS 1 - 2 rounds hit
4e Rules
Hit location 1: Head
14 SP (Exceeds SP of head resulting in death)

Hit location 2: Left Upper Torso
Failed shock roll
8 SP, 13 BP

New Rules (Treating each hit individually)
Hit location 1: Head
0 SP, 1 BP

Hit location 2: Left Upper Torso
0 SP, 1 BP

New Rules (Adding each hit and using as a single hit)
0 SP, 1 BP

2) DoS 8 - 3 rounds hit
4e Rules
Hit location 1: Right Knee
Failed shock roll
11 SP, 15 BP (Exceeds SP of location rendering leg below knee unusable)

Hit location 2: Right Upper Torso
11 SP, 11 BP

Hit location 3: Abdomen
Failed shock roll
11 SP, 15 BP
Imparment
Critical Bleed

New Rules (Treating each hit individually)
Hit location 1: Right Knee
8 SP, 8 BP

Hit location 2: Right Upper Torso
8 SP, 8 BP

Hit location 3: Abdomen
8 SP, 8 BP

Note: Target dies from wounds

New Rules (Adding each hit and using as a single hit)
Dead

3) DoS 5 - 3 rounds hit
4e Rules
Hit location 1: Left Upper Arm
Failed shock roll
12 SP, 17 BP (Exceeds SP of location rendering left arm unusable)

Hit location 2: Left Hand
Failed shock roll
12 SP, 17 BP (Exceeds SP of location rendering left hand unusable)

Hit location 3: Right Elbow
Failed shock roll
12 SP, 17 BP (Exceeds SP of location rendering right arm below elbow unusable)

New Rules (Treating each hit individually)
Hit location 1: Right Knee
1 SP, 1 BP

Hit location 2: Right Upper Torso
1 SP, 1 BP

Hit location 3: Abdomen
1 SP, 1 BP

New Rules (Adding each hit and using as a single hit)
Dead

There are some unusual results, but largely the rules seem to cause similar damage. The outliers are Test set 1 case 4 where the calf was hit. The proposed rule resulted in death, while the 4e rules only had a dismemberment with a critical bleed. While that will result in death unless treated in a timely manner, it is still a difference. The other outliers were Test set 2 cases 1 & 2. In case 1, the proposed rules had light while the 4e rules had that be a fatal headshot. In case 2, the proposed rules resulted in death while the 4e rules result in serious, but not necessarily fatal wounds. The critical bleed in the abdomen is serious, but you have time to treat and possibly correct the bleed.

The proposed rules do make for much faster combat, but the damage from Heavily wounded / Severe injury seems to scale too quickly from high and exceptional DoS making any such hit almost assuredly fatal. Scaling the damage down to half DoS in these cases might help.

The headshot doing so little damage also feels off. We should be able to rely on common sense rulings, but maybe not.

Those are my initial tests and comments. Hope they help.

[mmartin798]

I just realized that I did not do hit location properly for the proposed rules. I used the same location I rolled for the 4e hits as indicated on the chart. I did not just reverse the digits on the hit roll to determine the hit location. Though reversing the digits as the location does seem to mix up the locations, it does make headshots much more likely when the to hit roll is less than 30%. In that range, all torso hits are only twice as likely by reversing digits, rather than three times as likely using the chart by itself. Just something to consider.

[knightofrubus]

That's fair. I might need to tweak some things though I must admit it does technically do its proposed purpose.

The burst fire is definitely interesting. I was truthfully worried I had damage values on a wrong scale in terms of SP between the two but around ~10:1 was what I was figuring.

The head thing also strikes me as odd. That though interesting I'll need to mill on that.

[StainlessSteelCynic]

Just as a small point of note about electricity and damage from it, electric shock is probably the most common form of injury by electricity, when you start getting into electrocution you're talking death or severe injury.
Where it will get "fun" working out damage rules is determining the amperage of the electricity - "high voltage can harm you but high amps will kill you" sort of thing.

As a very rough first look, you could say that high voltage (e.g. 1000 or more) will injure someone and excessively high voltage (e.g. 10,000 or more) will kill them.
A current of just 10 milli Amps (i.e. 0.01 Amp) will give you severe electric shock and 100 mA (0.1 Amp) will cause severe contractions of the muscles and this can upset the heart beat which sometimes causes death.
2000 mA (2 Amps) will cause burning of body tissue and will cause unconsciousness along with muscle paralysis. The heart beat is interrupted and death is very likely.

What I have no clear idea of though, is how to go about modelling that in the rules (particularly as I am not very familiar with any of the rules, regardless of edition).

The following link describes damage from electric shock and from electrocution far better and has a useful chart for damage by Amps
https://www.scienceabc.com/humans/how-many-volts-amps-kill-you-human.html

[mmartin798]

Amperage is what the 4e rules use to determine electric damage, so the document you reference would be useful to help the conversion.

For these rules to work, we need to make sure all the types of damage that can happen are addressed in some manner. The list is:

Ballistic
Explosive
Impact (including hand-to-hand)
Electricity
Burns
Hyperthermia
Hypothermia
Starvation/Dehydration
Poison/Venom
Radiation

Some are more important than others, since you can arrange a game to almost ever encounter the problem, and others can be handled kind of trivially.

[knightofrubus]

So slight update(I'll try tackling various other horrible ways to die later). I tweaked Severe Injuries they now will do a flat 2SP/BP loss however they also inflict 'Traumatic wounds' which are kinda the middle ground between being upright and lying on the floor bleeding. Their severity is determined by the attackers DOS. I might also rejigger the math so there's no multiplier involved and Thresholds are resolved against straight E-factor DP.

[knightofrubus]

Amperage is what the 4e rules use to determine electric damage, so the document you reference would be useful to help the conversion.

For these rules to work, we need to make sure all the types of damage that can happen are addressed in some manner. The list is:

Ballistic
Explosive
Impact (including hand-to-hand)
Electricity
Burns
Hyperthermia
Hypothermia
Starvation/Dehydration
Poison/Venom
Radiation

Some are more important than others, since you can arrange a game to almost ever encounter the problem, and others can be handled kind of trivially.

Im thinking Impact damage will largely be handled the same as Ballistic that is it causes damage /end thought.

The others will need some reworking though. I might also stipulate hand to hand will only do Endurance damage unless they're trained in CQC.

[mmartin798]

The others will need some reworking though. I might also stipulate hand to hand will only do Endurance damage unless they're trained in CQC.

You may need to address the situation one of my groups used a lot, the knock-out attack. As stated on p97, this is a called head shot with a non-lethal weapon on an unaware target. Currently, if it is a hit on the neck or head, the attack does normal SP damage and 2X damage directly to Endurance. Since you are scaling back the damage to match the lower SP/BP, you will need to up the factor of damage to Endurance or they will never knock anyone out.

[knightofrubus]

You may need to address the situation one of my groups used a lot, the knock-out attack. As stated on p97, this is a called head shot with a non-lethal weapon on an unaware target. Currently, if it is a hit on the neck or head, the attack does normal SP damage and 2X damage directly to Endurance. Since you are scaling back the damage to match the lower SP/BP, you will need to up the factor of damage to Endurance or they will never knock anyone out.

Definitely something I gotta address. Hmmm I'll have to see what I can tweak there. Thoughts on the Traumatic wounds? I'll need to do some testing this weekend for sure.

[mmartin798]

First impressions on the traumatic wounds, I like them. I haven't run them through a simulation, but they seem reasonable on their face. I'll let you know if my opinion changes.

[knightofrubus]

First impressions on the traumatic wounds, I like them. I haven't run them through a simulation, but they seem reasonable on their face. I'll let you know if my opinion changes.

Glad to hear. I think they might be how I model various other forms of trauma such as Radiation sickness and hypothermia though I've gotta reread those entries and see what tweaks will be needed.

[knightofrubus]

So a rough Explosives rule. Addtionally, there's now a hard limit on how many Traumatic injuries you can suffer before being dead outright.(10's of CON attribute).


EDIT: added in clarity on what Traumatic wounds will do if left untreated, a hard limit on how many a character can handle andwhat to do when a weapon that uses Traumatic Force damage hits.

Explosive: weapons that deal explosive forms of damage are treated as such: divide the Damage by 10. (Damage÷10)
This is the Trauma Factor(TF). Characters hit by such weapons immediately suffer that many Traumatic wounds. On vehicles they reduce its Structure by the net damage ÷10, or divide the Explosive armor value by Ten and apply the net damage of the new value- Trauma factor.

If the weapon has fragments, roll for a location for each hit except the first. This will always be whole body damage.

[knightofrubus]

Changed some core math around(no need to multiply)
Added in what happens when you're lit on fire might need some further tweaks to that but should at least 'work'. The math changes came around after talking with the lead designer for 4th as it might be a direction the next edition eventually goes.

[knightofrubus]

Hyper and hypothermia rules are now in. Also, removed the penalty from SP loss.

[knightofrubus]

One last update as now Non-lethal damage is factored as is how automatic fire and a few other did bits operate. Calling it a tentative 'done' for now.