Armor as dice is a good way of simplifying and speeding some aspects of GURPS combat. It makes it pretty easy to determine if an attack penetrates armor – do the damage dice exceed the armor dice? If yes, injury occurs. If not, it doesn’t.
Simple and binary. Maybe too much so. In my Alien Menace game, when +Peter V. Dell’Orto or +Jake Bernstein got tagged by a blaster for 3d(5) against 10d armor there was no doubt as to the outcome – you were going to take 1d injury per shot. Period.
In that case, the chance of injury was 100%, and the average injury was caused by 3.5 points of penetration, maximum 6 points.
In rules-as-written GURPS you’d roll the 3d damage against 1/5 of DR 35 or DR 7. That’s about a 12% chance of no injury at all, average damage was 3.68, with a maximum of 11 points. You get an injury more than the maximum 6 points using armor as dice about 20% of the time.
If I increase the overmatch by as little as 1d (3d penetration vs 1d effective armor, or getting hit with 3d(10) instead of 3d(5), normality reverts itself, with 1% chance of getting by unscathed, and a tiny fraction of the time getting higher than the max Armor as Dice value of 12.
So this is really an extension of the edge case of when penetration is more than armor, but by less than about 1d.
I think the solution to the problem, such as it is, is that if penetration less armor is lower than or equal to 1d+1, add 1d-4 to the penetration and roll it. Sometimes it’ll come out as a non-penetration, sometimes you’ll get in a few extra HP . . . but mostly it’ll keep the right flavor. You either totally overmatch the armor and always cause injury, or the blow pings off and is no real threat.
But as it happens, the deliberate challenge I posed to my players – weapons that just barely overmatched their torso armor – fell right smack into an edge case.
Who’d a thunk it?
This post started as me wondering how to keep the mystery for the players. They know their damage rolls (usually but not always 6d for the rifles), but by only rolling injury, they know exactly how strong their foes’ armor is. That means I have to roll all damages (which is less fun for them) if I don’t want to give key bits of tactical data away, such as how strong the armor is.
That’s a real downside to Armor as Dice, since if you roll at all, you are either in the middle of the edge case or blasting through. Maybe that’s OK, but I like the feeling as a player of rolling my hit and damage rolls, then seeing the effect. In a +RPTools world, or +Roll20, this is often done as a macro: Bob rolls 10 against a skill of 14, succeeding by 4. He hits twice, and rolls 6d6 and 6d6 for 16 and 29 points of damage if his foe fails to defend. Very common MapTool and Roll20 macros there. When playing on a VTT, that sort of automation does speed the game.
For Alien Menace, I’m not too worried about metagame knowledge from my players – they’re long-time gamers, authors, and all-around good guys. But as a general case, while I like armor as dice for many reasons, this isn’t one of them.
A solution by +Luke Campbell offered by Varyon
Over on the GURPS Forums, Varyon comments that one thing that would fix this quite a bit is to change “roll injury as Nd” where N is the penetration dice less the armor dice to “roll injury as 1d x N, where N is still the same.
So the players, on any injury, are rolling 1d. No information need be given out other than the fact that armor was penetrated. Bonus, from my perspective, is it increases the variability of injuries. If you like grazes and hitting the vitals with a 1d roll . . . I wonder if it can be the same roll. If you slam down a 1, you check to see if it was a graze or not (with N being max damage), and if you roll a 6, you have hit something important, and can increase the damage as a result.
Bah. That’s another post. For this one, I think treating Nd+M as 1dxN+M is the answer I was looking for.