In case it wasn't noticed, the Opening Post was updated to include the Shield Protection Factor parameter and associated conclusions. I've also tested other parameters, in accordance with Replier suggestions.
Observations
- Bucklers provide almost the same level of protection as shields. The largest differences lie at low skill levels, where shields may add up to 15% more blocking chance.
- At high levels of the Shield User skill shields are superior to bucklers by only a few percents of blocking chance.
It might be worth trying to directly modify the BLOCKCHANCE values in the raws to see what effect they have - in the stock raws, bucklers have a BLOCKCHANCE of 10 while shields have a BLOCKCHANCE of 20. It would also be useful to see how the MATERIAL_SIZE and UPSTEP values affect shield performance.
Here are the results, all collected with Marksdwarf = 10 and Shield user = 3, since in unmodded shields this results in a 50% Probability of Blocking:
From the data, it appears that neither UPSTEP or MATERIAL SIZE have any effect on the effectiveness of shield protection.
BLOCKCHANCE seems to be the only parameter of relevance. Shields with the same BLOCKCHANCE as bucklers had similar blocking capabilities, namely a PoB of 43% vs the buckler's PoB of 40%. The 3% difference between samples is within the range of predicted error.
If someone were to equip enough shields/bucklers, would they be impervious to all forms of attack?
Inspired by Urist da Vinci's suggestion, I made a very simple modification by giving Arena Dwarves the body_default of HUMANOID_6ARMS instead of plain HUMANOID. This effectively allows dwarves to carry up to 6 pieces of equipment and carry the test further. The results are given below.
The shield's PoB values follow a curve which supports the hypothesis that the penalty is reapplied recursively i.e. it is applied again to each additional shield on top of the earlier penalties. However, the the PoB values do not confirm the penalty to be 50%. According to
itg's calculations, a 50% penalty would lead to a maximum PoB of 71.1%. Since the PoB rose above 84% with 6 shields...
I made a few guess-based calculations, and I am estimating the penalty is somewhere between 40% and 33%. That is, each additional shield has a PoB which is from 60 to 67% the value of the previous one. I'll refine my calculations when I have some spare time. To summarize, equipping a lot of shields will not be amazingly useful if Your Shield User skill level is very low to begin with, due to the hypothesized recursive penalty. If at a given scenario You have a base 1-shield 10% PoB, then an additional 5-6 percent isn't all that notable (int terms of SPF). At high Shield User skill levels, however, multiple shields will upgrade Your already amazing blocking ability to insanely amazing.
Rather than a dual wielding penalty, it might be an off-hand penalty.
i.e. your dwarf might block better if he's wielding the shield in his primary hand. Since the second shield goes in the off hand, it gets a penalty.
Try equipping your victims with a shield and a weapon. (can you pick which hand the shield goes in? Try both ways if you can!)
This was an interesting take on the problem, so I tested it out. One test was with dwarves wielding a battle axe and a shield, and the other with a shield and a battle axe. This was confirmed to allocate the shield to different hands. The results are shown below:
It appears that dwarves are ambidextrous, at least as far as shielding is concerned. There are no significant differences between using the shield right-handedly or left-handedly. Wielding a weapon in addition to the shield also makes no difference on shielding ability, since the results are the same as in the case of dwarves wielding shields alone.
this should go on the wiki, there isn't even a shield page on the wiki
The wiki page doesn't have a page for any protective equipment. They are all discussed on the collective "Armor" page. I'll make a small update on the wiki on shields and the Shield User skill, if no one else will.