Has anything changed about the terrain damage formulas, over what's written about the OG in UFOpaedia?
The reason I'm asking this is that I've broken terrain damage in some way, and since I'm not exactly sure what the current formulas are, I'm not able to fix things I don't understand.
Specifically, I've changed all Alien(-inspired) explosives to ResistType: 5 (plasma). The end result is, these explosives now do their nominal damage against terrain, resulting in hilarity like blowing the whole top off a Terror Ship with a Blaster Bomb.
Fiddling around with ToTile damage modifiers, I can resolve this on a weapon-by-weapon basis. A bit hackish, but fine. As a corollary, I tentatively conclude that terrain has 50% armor against explosives and 0% against plasma.
Now comes the weird part. I have two plasma projectile weapons, one with 100 power and the other with 120, both using the 2d100 damage model. If UFOPedia is to be believed, neither should be able to pierce outer UFO walls (armor 100), since 120 * 0.75 = 90 < 100. In practice, the 120-damage weapon pretty much obliterates UFO walls at will and the 100-damage version does so with great regularity, maybe 50-60% of the time as a guesstimate.
I've also seen Dioxine claim that projectile damage is 2/3 - 4/3 of nominal damage. That would make it 50% and 75% chance to blow holes in flying saucers, respectively. Given that I did not do any rigorous testing, this is pretty consistent with my experience. So far, so good.
I then changed the ToTile damages to 60%, making these two weapons effectively do 60 and 72 damage against terrain. Dioxine's formula now disallows any UFO wall destruction: 100*0.6*4/3 = 80, 120*0.6*4/3 = 96, both less than 100. UFOpedia obviously does so as well. But in reality I was still blowing away walls, a small trial run gave me 4 penetrations/28 hits and 7 penetrations/29 hits, making the destruction chances of vvery roughly 10% and 25%.
Since my base is Solarius's X-COM Files, an extensive mod in itself, plus a lot of fiddling with parameters I don't apparently understand well enough, it's entirely possible that there's another factor here that I'm not aware of that screws up the calculations. I'd really like to understand what exactly is going on, though. I'm unable to post ruleset snippets right now, but can do so tomorrow if requested.
Oh, and all these plasma weapons have ToArmorPre: 0.1, but as I understand it, walls and other terrain don't really have any armor values that this would apply to.