Note: Original change is from xNetHack by copperwater <aosdict@gmail.com>,
but this commit comes from HACKEM-MUCHE by Erik Lunna, with
some minor code formatting.
From xNetHack commit a0a6103bea:
'The original goal: nerf item destruction using a method I initially
proposed for SpliceHack, in which the number of items subject to
damage from any single source is limited by the amount of damage the
effect caused. The intent was to be more fair all around and prevent
aggravating situations where, for instance, a chest shock trap zaps
you for 4 damage and immediately ten of your rings and wands blow up.
Problem 1: no easy way to limit the items destroyed without biasing
heavily towards the start of the invent chain. The old code was able
to get away without bias by just indiscriminately destroying
everything eligible with a 1/3 chance. Here, I had to introduce
reservoir sampling in a somewhat more complex form than I've applied
it elsewhere, since there are a pool of potential items.
Problem 2: destroy_item no longer worked remotely like destroy_mitem,
which still destroyed 1/3 of items indiscriminately. Commence the
process of squishing them into one function that handles both the
player and monsters. (Which required making a lot of adjustments to
destroy_one_item, now named maybe_destroy_item, on nits such as
messaging and when to negate damage. An annoying consequence of the
merge is that in the player case, their HP is deducted and they can
be killed directly, but for monsters they need to add up the
destruction damage and return it.)
Unifying destroy_item and destroy_mitem has some advantages: in
addition to the obvious code duplication removal, it ensures monsters
now take the same damage as players for destruction (previously they
took a piddly 1 damage per destroyed item). Now when you hit
something with Mjollnir and their coveted wand of death breaks apart
and explodes, you at least get the satisfaction of knowing they took
the standard amount of damage from it. Monsters also now get
symmetry with players in having extrinsic elemental resistance
protect them from item destruction, and damage negation from item
destruction if they were appropriately resistant.
Problem 3: a lot of callers didn't preserve the "amount of incoming
damage" that this refactor relies on. E.g. if the defender resisted
that element, the local dmg variable would be set to 0. So I had to
do some wrangling with callers to save that original damage
value. The rule of thumb is: all *incoming* damage counts. So that
includes the player's spellcasting bonus if applicable, but not
things like half damage, negation due to resistance, or extra damage
due to being vulnerable to cold/fire.
Then I figured, while I'm here let's get rid of all those silly cases
where destroy_items is called multiple times for various different
object classes, and cut the object class parameter out of it. This
has a few minor effects:
- Places where different object classes previously rolled
independently for destruction to happen at all now roll
once. (Which, by my calculation, generally means less incidences of
destruction - a fire attack now won't have three separate chances
to hit your scrolls, potions, and spellbooks. On the flip side, a
lucky roll will no longer save an entire object class in your
inventory.)
- Callers can no longer specify different probabilities for
destroying different object classes. The only place this was really
used was to call destroy_item with a slightly lower probability on
SPBOOK_CLASS. With the nerf in this commit, less of them ought to
be destroyed anyway.
- A very edge case of where explosion-vs-monster damage was totted up
differently for golems, which could result in differences of a hit
point here or there.
- All object classes being processed in one go means that less items
are destroyed than would be if they were still processed
independently. This is not really visible compared to the old
baseline of just destroying 33% of everything, but would be a
marked difference versus a copy of the game that still called
destroy_items separately for different object classes. To
compensate, I adjusted my planned damage-to-destruction-limit
scaling factor down from 8 to 5.
Not done: merging in ignite_items(), though that would probably be
really easy now.'
Notes from porting from xNetHack:
- It might be necessary to reexamine at all the conditional checks for
calling destroy_items. Because item destruction is much more
restrained and uses the actual damage from an effect, we might now
need to check 'if (!rn2(3))' and similar in all the places item
destruction occurs.
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