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IDProjectCategoryView StatusDate SubmittedLast Update
0011772Dwarf FortressDwarf Mode -- Combatpublic2021-06-27 20:402022-03-18 19:01
Assigned To 
PlatformOSOS Version
Product Version0.47.05 
Target VersionFixed in Version 
Summary0011772: (Almost) Everything is 10 times as dense as it should be
DescriptionWeight in DF is weird. I went over [^] and noticed that the weight of everything is multiplied by 10 from its intuitive value (density * volume). Almost everything is therefore ten times as dense as you’d expect, with a few exceptions like weapons ( [^]) (7kg = 800ml of axe * 7.85 kg/litre, not 800ml of axe * 78.5 kg/litre).

I thought about this in the back of my head and realized that this is why falling objects are so incredibly dangerous (0005945): an ordinary piece of pig tail cloth is denser than real world lead when you multiply its density by 10 (1.52 g/cm^3 of plant fiber * DF factor of 10 > 11.34 g/cm^3 of real world lead). Even a seed (density 0.6 g/cm^3) is more than twice as dense as most stones (2.67 g/cm^3) when you multiply its density by 10. When you drop seeds and cloth on your dwarves, you're actually dropping stone and lead bullets on their heads.

But since everything in this game doesn't seem to be about ten times as heavy as it should be, I did some more digging. When I went over the size of objects, I noticed that they seem to be too small by a factor of 10. If you multiply each one by 10, you get a reasonable value: a statue is 60 litres, or the size of a dwarf, instead of being the size of three 2-litre soda bottles. A chest is 20 litres instead of being the size of a 2-litre soda bottle. A stone boulder is 100 litres, which means a wheelbarrow can fit one of those things instead of ten and a minecart five of those things instead of fifty. An anvil is now 10 litres instead of being half the size of a 2-litre soda bottle. A drink is now a 2-litre soda bottle’s worth of liquid instead of being less than a cup. Stuff like that.

In other words, as far as I can tell, DF includes two weird factor of 10 discrepancies that cancel out. Everything is ten times as small as it should be (except weapons and perhaps a few other exceptions), but everything is ten times as dense as it should be (again except weapons), so upon first inspection everything looks fine. But behind the scenes everything is ten times as dense as it should be, which makes cloth denser than real-world lead and seeds deadlier than real-world bullets. To fix that, just reverse the changes: multiply the size of almost everything by 10 and remove the hidden factor of 10 multiplier on density when calculating weight.

TL;DR: Make everything bigger but less dense to fix bug 0005945, the falling objects lethality bug.

(Originally posted at [^] & [^])
Steps To ReproduceLook at the weight of this galena bed: [^] It's 225 kg, or 10 times as much as it should be if the volume of a bed (3000 cm^3) was multiplied by the density of galena (7.5kg/litre). Now compare that to the iron axe from, [^] which weighs as much as you'd expect given its volume and density rather than 10 times as much. Clearly the effective density of in-game items is more than what you'd expect from their listed densities.
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spdx (reporter)
2022-03-18 19:01

i think this stems from a confusion of mass and weight? mass is a property of matter whereas weight is the force an object with mass experiences when in a gravitational field. weight = mass * gravity, gravity being the mystery 10 here. hope this helps

- Issue History
Date Modified Username Field Change
2021-06-27 20:40 WindComeCalling New Issue
2021-06-28 09:48 Flying_Teasets Issue Monitored: Flying_Teasets
2022-03-18 19:01 spdx Note Added: 0041234

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