Rework of explosive damage

[chaosvolt]

Is your feature request related to a problem? Please describe.

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Currently, explosives have been reworked to be basically useless against terrain. C4 no longer works against mundane walls, even mininukes do very little to terrain. On top of that, the damage also has a severe effect on their usefulness against monsters. Mininukes again are a good example, dealing a level of damage that isn't even enough to kill a hulk.

While obviously fixing their damage would increase how dangerous most explosives are to the player, I feel like this isn't undesirable. Explosives that give shrapnel damage instead of blast damage are ALREADY extremely dangerous to players, NPCs, and monsters alike, so it would be reasonable and consistent for powerful blast-damage explosives to be something you don't want to play around with. Plus, the upper end of blast-focused explosives still deal enough damage to be nasty for the player to face, disproportionately so compared to their usefulness against monsters. That same mininuke that many top-tier monsters will survive would still be powerful enough to kill just about any PC, for example.

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One first needs an idea of what type of terrain any given explosive should actually have at least 50% odds of destroying when 1 tile away (i.e. set right next to a targeted wall). I'll list as many suggested values as I can here, any other suggestions and additions will be added to the table as they come up:

Item	Target
Pipebomb	Standard windows
Grenade	Closed doors, possibly boarded up doors
Dynamite	Mundane domestic walls
C4	Brick walls, possibly concrete
Dynamite bomb	Solid rock
Mininuke	Metal walls, possibly whatever is the absolute strongest wall in the game

I'd suggest we start by referencing DDA's realismic values for explosive power in grams of TNT, and convert it back to damage by dividing it by the damage factor that seems to be in the hardcode: 2/15 (or 0.1333). This gives us a rough starting point to test on whatever we feel that explosive's desired target should be.

If it can't destroy its desired target terrain reasonably often then buff until it does, if it's tested and found too effective against significantly stronger terrain meant to be a different explosive's primary target, then lower it until the value works best against the target terrain. If possible damage should also favor an amount that makes it reasonably worth the effort of obtaining/crafting it against monsters.

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[Relgar]

DeltaEpsilon / @acssimpson has mentioned that the reason why it appears weak is that the explosion is being stopped from being propagated the moment it runs into a tile. After this has been done all that needs to happen should be tweaking damage of the explosives to be outside the max bash damage range, I'm guessing. See below:

Cataclysm-BN/src/explosion.cpp

Line 169 in c15e143

if( g->m.impassable( pt ) && pt != p ) {

I would also like to take this opportunity to suggest splitting explosives up by material so that they have differing strengths. Right now you can use multiple explosive types to make an improvised explosive, but there is no universe where a heap of match stick powder can produce the same power as RDX.

Edit: Turns out this was working as expected, only problem was that this one liner that was quartering the amount of bashing force for some unknown reason aside from the tile the explosive was on. I'm looking at the terrain vs explosive data if this is reverted to full force as we can control for the bashing power with radial damage dropoff.

Cataclysm-BN/src/explosion.cpp

Line 181 in c15e143

const float bashing_force = force / 4;

[Relgar]

BFN has also previously implemented radial damage so that dropoff occurs once you're 50% away from the epicenter. This can be rolled into your proposed framework so that walls near the epicenter get blown apart, but the further away they are the less likely this is to happen.

[Relgar]

To check the math, here is a selection of the more common walls and doors. The way bashing damage works is that if your bash / explosion damage is between the min and max (inclusive) that'll be your chance / max to bash the terrain. As such, midpoint (rounded down) should represent a 50% chance of destroying the terrain.

Terrain	ID	STR_MIN	MID (RD)	STR_MAX
Window	t_window	3	4	6
Glass Door	t_door_glass_green_c	6	13	20
Wood Door	t_door_c	8	44	80
Boarded Up Doors	t_door_boarded	15	47	80
Reinforced Wood Door	t_door_glass_green_c	18	59	100
Brick Walls	t_brick_wall	60	110	160
Normal Wall	t_wall	30	120	210
Reinforced Glass Door	t_reinforced_door_glass_c	40	125	210
Metal Door	t_door_metal_c	80	165	250
Concrete Wall	t_concrete_wall	70	235	400
Solid Rock	t_rock	100	250	400
Metal Wall	t_wall_metal	200	400	600
Resin Wall	t_wall_resin	250	475	700

In comparison, here is the list of explosives that we have:

Name	JSON Dmg.	Curr. Dmg	Prop. Dmg	50% Dmg	Ex. Range	50% Range	Shrap Dmg.	Shrap. Rng.	Hardest Terrain at Epi	Hardest Terrain at 50%+ Distance
Can Bomb	0	0	0	0	0	0	50	5
EMP Bomb	50	12	0	0	7	3	0	0
Improvised Pipe Bomb	20	5	20	10	4	2	70	8	Glass Door	Window
Small Improvised Frag Device	50	12	50	25	6	3	150	20	Glass Door	Glass Door
Improvised Grenade	40	10	80	40	3	1	40	6	Boarded Up Doors	Glass Door
Grenade	40	10	80	40	3	1	80	6	Boarded Up Doors	Glass Door
Dynamite Bomb	70	17	100	50	6	3	100	10	Reinforced Wood Door	Glass Door
Dynamite	100	25	210	105	6	3	0	0	Reinforced Glass Door	Reinforced Wood Door
Improvised Demolition Charge	150	37	250	125	6	3	0	0	Metal Door	Reinforced Wood Door
C-4 Explosive	200	50	400	200	8	4	0	0	Solid Rock	Brick Walls
ANFO Charge	250	62	500	250	12	6	100	20	Solid Rock	Metal Door
Improvised Barrel Bomb	200	50	600	300	15	7	80	20	Metal Wall	Metal Door
Mininuke	300	75	1000	500	20	10	0	0	Resin Wall	Solid Rock

So we can immediately see that currently, a mininuke can't even begin to damage solid rock and onwards. To address this I would first suggest removing the bashing_force = force / 4 line as it is the main culprit in reducing dmg vs terrain. It will be more consistent to use the same damage values in JSON vs terrain as well as vs monsters.

Secondly, to bring this up to the 'expected' things the explosives can do as initially outlined, I would first buff damage to more than 50%, perhaps even closer to 100% as the last thing you envision an expertly planted C-4 bomb to do is failing to blow up the wall it was planted on. The way we would control overdoing the damage would be with the damage dropoff that was initially coded as 50% dmg once the explosion has reached 50% of the distance from the radius. A more nuanced approach could be taken such as 100%, 80%, 60%, 40% corresponding with distance. This would mean, even at the furthest edge, an increase of 160% vs what is currently occurring (400% * 40%).

I'll sleep on this for a bit and tweak the numbers, but please have a look at the initial proposed damage values, keeping in mind that we'll use damage falloff to prevent overbashing.

[chaosvolt]

Looks like a good start, yes. Sorry that I haven't had time to try to tinker with this myself, been busy with offline things that keep coming up.

[Coolthulhu]

I'm working on a general "terrain being bashed" update, so I'll handle it there.

[Relgar]

Some additional bits: there are also ammo effects that need to be considered, and what they are envisioned to do. I just loaded some of these like the RPG-7 and LAW, and they barely dent a normal car. See below values, these will need to be 'upgraded' to actually take out vehicles for some weapons. Maybe an EXPLOSIVE_AP flag:

Name	JSON Dmg.	Curr. Dmg	Prop. Dmg	50% Dmg	Ex. Range	50% Range	Shrap Dmg.	Shrap. Rng.	Hardest Terrain at Epi	Hardest Terrain at 50%+ Distance
FRAG_SMALL	0	0	0	0	0	0	30	3
FRAG	0	0	0	0	0	0	50	5
FRAG_BIG	0	0	0	0	0	0	100	7
EXPLOSIVE_TINY	20	5	40	20	2	1	0	0	Glass Door	Glass Door
EXPLOSIVE_SMALL	40	10	80	40	2	1	0	0	Boarded Up Doors	Glass Door
EXPLOSIVE	50	12	250	125	3	1.5	0	0	Metal Door	Reinforced Wood Door
EXPLOSIVE_BIG	70	17	400	200	5	2.5	0	0	Solid Rock	Brick Walls
EXPLOSIVE_HUGE	100	25	600	300	8	4	0	0	Metal Wall	Metal Door

Ammo Effect	Ammo	ID
EXPLOSIVE_HUGE	152mm ATGM HEAT	atgm_heat
	84x246mm HEDP rocket	84x246mm_hedp
EXPLOSIVE_BIG	84x246mm HE rocket	84x246mm_he
	PG-7VL 93mm rocket	RPG-7_ammo
	66mm HEAT	66mm_HEAT
EXPLOSIVE	PG-7VR 64mm/105mm rocket	RPG-7_pg7vr
	TBG-7V 105mm rocket	RPG-7_tbg7v
	explosive homemade rocket	explosive_hm_rocket
EXPLOSIVE_SMALL	explosive arrow	arrow_exploding
	explosive crossbow bolt	bolt_explosive
	Boeing XM-P plasma rifle	plasma_rifle
	PPA-5	plasma_gun
EXPLOSIVE_TINY	20x66mm buckshot	20x66_shot

Then there is also the problem of holes being randomly generated (as discussed with @Coolthulhu) when the roll hits min-max instead of radiating from the epicenter in a clear, connected, logical way. This affects the pothole-effect you can get from explosions as below (mininuke in a evacuation center basement w/ 700 dmg @ full bash force):

[Coolthulhu]

they barely dent a normal car

The problem is with car values, not explosives. They have massive armor.

[Relgar]

That's fair, another rebalance to do!

[Relgar]

I've updated the numbers - BFN prefers a 50% dmg dropoff so I'm trying to make it so our little nuke can take out anything and still cause a respectable amount of damage at falloff. Please have a look at let me know if the numbers seem off.

[chaosvolt]

Important side note though: remember that the damage probably needs a look too, removing the arbitrary quartering of effect on walls is only part of the problem. The way that a grenade can potentially be more lethal to monsters than most high explosives because fragment explosives still have massive damage while blast-focused explosives don't is still a discrepancy.

[Relgar]

Yeah I've taken a quick skim of the monsters - aside from the 10k debug monsters, the highest I found was mechs (550) and triffid hearts / trapped tendrils (500). The new damage values for the following can kill them in one shot, if they are at the epicenter:

• Huge Explosions (epicenter, tank shells)
• Mininukes (any range)
• ANFO charge (epicenter)
• Improvised barrel bomb (epicenter)

These explosives are rare enough / difficult enough to make that you wouldn't use them for no reason.

EDIT: You're also right about shrapnel / frag damage though - those will have to be taken in account together with the blast damage. And I got to rebalance the meme that is 'small improvised frag device'.

[chaosvolt]

Seems like that's a good start then, nice.