Sunday, November 16, 2014

Code Red - Dev Diary 8: Vehicle Destruction

Hello again and welcome to another iteration of our dev diary series!

Todays topic is Vehicle Destruction.

Image source:
The reason why I call it vehicle destruction rather than vehicle combat is simple: we´re focussing on destructio, as that´s the major area of change and the most important field to talk about.

In Force on Force, vehicles where destroyed by rolling firepower pool, pairing off successes against the defenders defense pool which was defined be the vehicle armor. If the attacker scored more successes than failures, he could roll on the damage chart and inflict some damage.

In my opinion this approach has several downsides. First problem is mixing all the relevant factors and steps into the firepower pool. As the firepower pool represents both hitting the target and achieving some terminal effect on the enemy, it can be very confusing to interpret.  Weapon systems with more damage potential (i.e. higher firepower) are much more likely to "hit" something (i.e. score some amount of successful die rolls) but may not inflict much damage by doing so as the result can b canceled out.  This produces a very strange picture of the events transpiring, with a lot of hits of very destructive weapons causing no effect on the vehicle.
On the other hand, it also means more destructive weapons are actually more likely to hit ANY target.  Firing with a big gun on a very light target yields a very high chance of destroying it, not just because the damage potential is higher, but because its much more likely to produce enough successes on a higher number of dice (which will usually be enough to trigger damage vs. low amount or armor dice)

Small example:
A TOW with Firepower 9D8  or so  is so much more likely to actually hit the target (expected amount of successes on TQ D8 = 5-6 dice or just a 0,026% chance to fail all 9 dice) than a 30mm autocannon with just 4D firepower  (average: 2-3 dice,  chance to fail all dice = 2,5%).
If you just look at the chance to fail all dice you´ll notice that a factor of 100 divides these cases.

So interpretting any successes as "hits" is not only the wrong interpretation, it´s also a problematic game design aspect. If anything, shouldn´t the 30mm cannon be much more likely to hit a target?  Less likely to penetrate it may well be, but hitting something is certainly easier with a lot of ordnance flying towards the target, which the autocannon can certainly do better...
Part of that problem is remedied by the different weapon damage and vehicle armor classifications, but it still plays a strong role.

Second problem with the FoF-approach is damage resolution. FoF features many tables with effects of different guns vs. vehicle types (which is another problematic aspect but I´ll not discuss this in full length...) but ultimately yields a stochastic result. We´ve seen Abrams shooting a T55 and the T55 survived unscathed because the Abrams rolled a 1 on his D12. Several times in a row...

You can never argue about luck or bad luck, but maybe the distribution is not ideal if my chances to escape certain death by a high end tank is still almost 50%? Only a 6+ on the relevant damage table results in immediate destruction of the tank, everything below that will only damage components...  

Anyway, I won´t go into too much detail here as FoF vehicle combat has so much subtleties and hidden pitfalls that make it hard to explain my point. In my opinion, the results feel wrong, and while in theory the mechanics should work and some measures have been taken to balance out the worst anomalies, the empirical evidence from gameplay is such that I think a change is required.

So what have we done with vehicle destruction for Code Red?

First of all, we´re split the process up again. You first have to hit the target, if you do so, you have to penetrate the armor. This immedialy reduces the amount of trouble caused by different weapon systems and their characteristics.

The to-hit roll is resolved like any other fire from heavy weapons and a rather trivial check. If you fail to hit your explosive charge might land elsewhere and cause damage in the area around your original target, depending on how bad your shot was.

Once you´ve hit, it´s all about penetration.  In my opinion that I generated by some basic research penetration relatively close to an all-or-nothing thing.  Either the vehicle is penetrated and some degree of damage is caused (with exponential effects as the level of penetration increases - minor penetration might just be survivable, major penetration will almost always kill the crew or the electronic systems and render the vehicle entirely inoperable)  - or it isn´t.

To check if a vehicle is penetrated, the attacker substracts the armor value from the penetration value (AT-power of the weapon). The result is a modifier that depends entirely on armor and penetration.

This modifier is then used to roll on a damage table, added on top of 2D10 (negative modifiers are thus substracted)

2D10 generate a nice bell-curve thingy with average results of 10 and 11 respectively.  Serious damage happens at 14+.  Assuming equal penetration and armor, the attacker thus has about 30% chance to knock out the target with a single hit. If the penetration exceeds armor, this might very well be much higher.

There´s also a very simple solution for critical hits, which is again kept secret to encourage you to look at the full ruleset once finished ;)

If a vehicle is hit and survives the damage, the crew must take a morale check - again, this check is modified by the modifier calculated earlier, so very small calibre weapons are very unlikely to scare the crew of a heavy tank, while something potentially dangerous might make them think twice!

Of course, things are always best explained by an example.  So let´s take an extreme case of a TOW vs. T55 from start to finish.

The TOW-gunner declares his activation against the T55, wins his reaction test and fires. The first shot misses the tank, but due to a bad reaction test the T55 hasn´t spotted the TOW team properly and is only able to put fire in the rough direction, to little effect.
The TOW then fires again in the next turn, this time hitting the T55.
A TOW(-I) has a Penetration of 15, whereas the T55 only features a front armor of 7.

The armor is substracted from the penetration value (15-7 = 8), which results in a total bonus of +8.
Now, 2D10 are rolled and +8 are added.  We roll a 16, add the 8  and get a 24.
Cross-referencing the damage table we can quickly guess that the tank explodes in a ball of flame, with munitions cooking off and parts and debris flying all around the place. 

And a second example, just to show some more variety:

A T72 fires on an M60A3 Patton, hitting it (otherwise the example would be quite pointless). With a penetration of 13 the basic T72 has slightly more penetration value than the M60 has on his front armor (10).
The total modifier is thus +3  (13-10),  2D10 are rolled for penetration. Result is an 11, which is barely enough to produce a 14 with the modifier applied. The M60 is penetrated and disabled. The crew has to take casualty checks for each member- two of the crewmen are dead, the remaining two bail out and get to cover somewhere nearby.

1 comment:

  1. Good AAR/Batrep. I make tank crews roll to hit, with crew bonus (+1 die to account for commander and gunner) and then roll damage. Each successful penetration gets 1d6 on the FoF damage table. With more than two penetration rolls, add the best two together.