[crossfire] Resistance calculation

[Mark Wedel]

Jochen Suckfüll wrote:

> * The damage factor from a vulnerability varies extremely, e.g. fire
> -10 doesn't hurt a newbie without fire protection (resistance 0) not
> much, but even breaks the fire immunity of a fireborn character.
> * Characters like the serpentman that start with cold -50 cannot get
> more than cold 50 even if they had a Cloak of Cold Immunity, since the
> maximum resistance cannot exceed 100-(accumulated vulnerability value).

  I believe those are intentional.

> * In general, even a little vulnerability hurts characters with a high
> resistance very much and renders the respective items almost unbearable.
> * Potions have to be treated separately, to overcome the penalty by the
> vulnerabilities.
> * The resistance cannot be less than -100, although there is no
> sane reason for this limit.

  That last point is probably more historical - I think at one point the 
resistance values where just in an 8 bit integer, limiting range to -127 to 
+127.  And it probably dates back to the days when discrete values didn't exist, 
but rather something with immune (+100), protected (+50) or vulnerable (-100), 
and no other values existed.

> 
> 
> I suggest to simplify the code and treat every protection or
> vulnerability the same by applying the accumulation formula above to
> both positive and negative resistance items.
> 
> Advantages are:
> * An item with resist -100 effectively doubles the damage taken, no
> matter if there was any resistance at all. Immune characters remain
> immune, a character with resist 30 will end up with resist 60, resist
> -10 will become resist -120.
> * That's very intuitive, because the resistance on the item tells
> exactly how the resulting damage is changed.

  Not sure I totally agree.  It makes more intuitive sense to me that if I have 
a resist +50 item and a resist -50 item, they balance out to 0.

> * We could have spells that reduce a monster's resistance without
> removing immunities. That adds another tactic element.

  That's an interesting idea.  I'm not 100% sure that the change is needed for that


> * We can even have powerful items with resist -1000 (ten times the
> current damage!) to counter other very positive features, without
> breaking the balance or making the item unusable.

  I don't think anything actually prevents a resist -1000 item right now, but 
such an item is clearly useless or meaningless.

  Off topic, but given items big negatives to offset the big positives they have 
may be an overused way to slip good items in the game.  Players are smart enough 
to use the right items at the right time, so all the negatives do is prevent it 
from being a general object that one uses all the time to an object used at 
specific times.

> * In general there is a better control over the effects of resistance
> values on items.

  Hard to really see how all this plays out.  And at a larger level, this all 
comes down to real damage.

  If my character has 200 hp, -50 racial fire vulnerability, under current 
system best protection I could get might be resist fire 40 (suppose I have items 
to get my positive resistance to 90)

  If I'm hit with a spell that does 50 points of damage, resist fire 40 means I 
take 30 points of damage.  However, under revised scheme, character would take 
15 points of damage, and if didn't have that -50 penalty, would only take 10.

  10 vs 15 sounds like a lot, but at 200 hp, not a big deal.  10 vs 40 is a lot, 
and really makes that resistance a handicap, which is its intention.

  If the resistance formula is changed, I think a lot of the races/classes may 
need rebalancing.

  Also, I haven't finished rebalancing the spells for crossfire trunk, and that 
will affect things also.  I certainly won't finish that before I go on vacation.

> The current resistance calculation is implemented in
> common/living.c:fix_object(). I would volunteer to make the required
> changes to the trunk version (2.0) if there is a common agreement.

  What you may want to try is put your no formula in, but do it with #ifdef 
NEW_RESISTANCE or something.  That provides an easy way for people to expirement 
with it and see the impact.  One of the things I learned with combat rebalancing 
is that it was often to just try something out and see what impact it is, vs try 
to speculate how things will get affected.