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[Wyrm]

Okay, this is not making sense. When I look at the raw for iron, the *_ELASTICITY arguments do not line up with what we know about it. The units can't be in kilopascals, since those figures are in the hundreds, and typical moduli are in the gigapascals. Also, the modulus -> elasticity score doesn't seem monotone:

Modulus (GPa)	ELASTIC SCORE
82	150
170	635
211	62

As you can see, the score goes up, then down.

Can someone help me unravel this mystery?

[Ramirez]

I believe the elasticity is related to the deformation at the yield stress, or it might be the breaking stress, I'm not sure. See adamantine, as it has 0 for all of the elasticities.

[CaveIn]

I have problems understanding what most of the *_YIELD, *_FRACTURE and *_ELASTICITY tags are for, tbh. It might just be me not doing the right searches on Google though!

[Wyrm]

Yeah, which means that adamantine is perfectly rigid (which violates special relativity, but that's another discussion). My first thought was that it was some scaling of of the strain at yield stress (given that is what would be available at large), but it doesn't work. The scaling factor is wild and wooly, varying by a full order of magnitude between their respective compression and tensile values, although noting that the tensile and shear values in the same material vary by only a few percent, but not between materials.

I have problems understanding what most of the *_YIELD, *_FRACTURE and *_ELASTICITY tags are for, tbh. It might just be me not doing the right searches on Google though!

I'm making the assumption that *_YIELD is the yield strength of the material — that is, the stress of the material at its elastic limit, while *_FRACTURE is ultimate tensile strength. Those are pretty straightforward, and consistent with what I know about the materials. It's *_ELASTICITY that is the oddball here.

What we need is Arrkhalz to explain how he balanced the materials in his mod.

[derigo]

It's not all THAT important what those values actually mean, unless you're researching to find accurate values for some custom material or something.  What's more important is what they DO.  I can tell you from loads of testing that the _YIELD values have everything to do with blunt weapon attacks, and nothing to do with edged attacks.  In the vanilla raws the only materials with valid _YIELD values are skin, rock, metal, and bone (maybe wood? I can't remember).  All the other materials are wrong.  By wrong I mean toady copied them from skin, and didn't remember to put some semi-valid placeholder there. 

This is why animal bite attacks don't hurt.  Bite and Claw attacks are blunt, and the _YIELD values for tooth, horn, and nail (and shell), are all the same as skin.  In essence, teeth are as "soft" as skin, when dealing with blunt attacks.  If you copy the _YIELD values from bone onto nail,tooth, horn, and shell, natural weapon attacks all of the sudden start working. 

[Ramirez]

I believe that it is the impact yield that determines impact damage (possibly affected also by the impact fracture and impact elasticity). Shear values are used in edged combat and I don't know what the torsion, tensile and compressive strengths are used for.

[Bishop36]

Is everyone who plays this game some kind of Physicist/Geologist/Artist ect?

[Zangi]

Is everyone who plays this game some kind of Physicist/Geologist/Artist ect?

No, but I suppose it attracts a fair share of em.

A lot of this stuff goes over my head too, so don't worry about it.  Well, you do have to at least understand the very basics to get some advanced modding going.

[Shaostoul]

Well, when I run into stuff I don't understand, I read up on it quite a bit and I do what I can to help me understand what it means. Mostly because of how much I do modding in this game.

[Wyrm]

It's not all THAT important what those values actually mean, unless you're researching to find accurate values for some custom material or something.

Well, this thread is in the modding forum, is it not?

[derigo]

What I meant was, you can estimate your values based off the values already in place and your knowledge of what the values DO TO THE GAME rather than trying to do research and find values on the internet.  If toady's sources are different then yours, you might end up with wildly different numbers, and not get the results you want.  This is especially true if you're trying to add a material that doesn't exist in the real world. ;p

@ramirez
Yes I'm sorry, I replied to the post from memory instead of actually checking what values were being discussed.   IMPACT_YIELD, IMPACT_FRACTURE, IMPACT_ELASTICITY determine blunt damage in combat, not _YIELD tags in general.  My bad.

Toady is pretty explicit about what the values are used for in his comments in the raws, at least in a general sense.  Maybe dividing them up so its easier to read will help?

"       Not used."

   [MOLAR_MASS:36000]
   [COMPRESSIVE_YIELD:120000]
   [COMPRESSIVE_FRACTURE:120000]
   [COMPRESSIVE_ELASTICITY:100]
   [TENSILE_YIELD:15000]
   [TENSILE_FRACTURE:15000]
   [TENSILE_ELASTICITY:100]
   [TORSION_YIELD:15000]
   [TORSION_FRACTURE:15000]
   [TORSION_ELASTICITY:100]
   [BENDING_YIELD:15000]
   [BENDING_FRACTURE:15000]
   [BENDING_ELASTICITY:100]
   [ABSORPTION:100]

"   Used for blunt-force combat, measured in KPa.  Data scattered around the net (used compressive strength).  All very spotty."

   [IMPACT_YIELD:120000] used marble
   [IMPACT_FRACTURE:120000]
   [IMPACT_ELASTICITY:100]

   Density information.  Not used for very much, but it comes up in inventory weight and fighting.
   [SOLID_DENSITY:2670]
   [LIQUID_DENSITY:3300]

"   Used for cutting calculations in combat, measured in KPa.  Data scattered around the net (used tensile strength).  All very spotty."

   [SHEAR_YIELD:15000] used marble
   [SHEAR_FRACTURE:15000]
   [SHEAR_ELASTICITY:100]

So 2/3 of the values aren't used for anything at all and can be ignored. 

[Djohaal]

Is everyone who plays this game some kind of Physicist/Geologist/Artist ect?

Smart games attract smart people

[Wyrm]

What I meant was, you can estimate your values based off the values already in place and your knowledge of what the values DO TO THE GAME rather than trying to do research and find values on the internet.

In many ways, this is exactly my problem: I don't know what *_ELASTICITY does in the game — not in the detail I need. If I did, then I'd be able to figure out the relationship between *_ELASTICITY and the corresponding elastic modulus.

Because I do know something about materials science, I'm able to translate Toady's comments concerning *_YIELD and *_FRACTURE into effects in the game. That they happen to line up with sources on the net is a big help.

If toady's sources are different then yours, you might end up with wildly different numbers, and not get the results you want.

Those are Toady's numbers! He was helpful enough to put what he believed the bulk, Young's, and tensile moduli of iron right there in the raws. It still doesn't make any sense!

This is especially true if you're trying to add a material that doesn't exist in the real world. ;p

Some of the materials I'm modding in do exist in the real world, and I want them to have realistic behavior.

[derigo]

What I meant was, you can estimate your values based off the values already in place and your knowledge of what the values DO TO THE GAME rather than trying to do research and find values on the internet.

In many ways, this is exactly my problem: I don't know what *_ELASTICITY does in the game — not in the detail I need. If I did, then I'd be able to figure out the relationship between *_ELASTICITY and the corresponding elastic modulus.

Oh god,  I'm sorry again, lol.  I totally misunderstood the premise of your post.  The lack of modulus identifiers in your original post threw me for loop and I totally misunderstood what you were saying.

Now that I'm on the same page as you, I still have something to say.  Nevertheless its important to be aware that the only the IMPACT_ELASTICITY and SHEAR_ELASTICITY values are (according to the comments) actually used by the game.  In the comments Toady says that the IMPACT_* values are based on the compressive strength.  A quick glance at the metals raws shows that he copied the IMPACT_ELASTICITY values straight from the COMPRESSIVE_ELASTICITY values (the bulk modulus).  And comparing the various values, its pretty clear its just an inverse relationship of some sort, I'm not going to find the slope(if its linear) here.  Here's a bunch of values sorted into order to make the relationship clearer

Code: [Select]

gold
[COMPRESSIVE_ELASTICITY:600] bulk modulus 180 GPa
Iron
[COMPRESSIVE_ELASTICITY:635]  170
copper
[COMPRESSIVE_ELASTICITY:771] 140
silver
[COMPRESSIVE_ELASTICITY:1080] 100
Zinc
[COMPRESSIVE_ELASTICITY:1542] 70
tin
[COMPRESSIVE_ELASTICITY:1862] 58

The SHEAR_ELASTICITY relationship is much less clear.  The values are clearly not directly proportional.

Code: [Select]

iron
[SHEAR_ELASTICITY:159] shear modulus 82 GPa
gold
[SHEAR_ELASTICITY:185] shear modulus 27 GPa
silver
[SHEAR_ELASTICITY:333] 30

SHEAR_ELASTICITY is either a derived value from some function using the moduli, or toady ignored the real world modulus values and pulled the numbers out of thin air to make the combat system make some kind of sense.  Here are some sample points.  If someone can figure out a relationship to derive the SHEAR_ELASTICITY from the 3 moduli, sweet.  It may or may not involve all 3 moduli. 

Code: [Select]

metal  Shear ELasticity        bulk mod(gPA)             young's mod(gPA)           shear mod(gPA)
Nickel         26                 180                        200                       76
zinc           116                 70                        108                       43
iron           159                 170                       211                       82   
gold           185                 180                       78                        27
bronze         200               180?(from gold)            110                       ???
silver          333               100                        83                        30
steel           500               160                       200                       ???
tin            66                  58                        50                        18
lead           179                 46                        16                        5.6               
aluminum       77                  76                        70                        26


At a glance, the comparison of nickel and iron, along with the suspiciously round numbers for bronze silver and steel lends weight to the "pulled from thin air" theory.  Nickel is an outlier, it doesn't seem to obey the same rules as the others, maybe its a typo?  If you're actually trying to find the relationship, I suggest throwing out bronze, steel, and maybe silver.  Here's the same list without the suspicious entries.

Code: [Select]

metal  Shear ELasticity        bulk mod(gPA)             young's mod(gPA)           shear mod(gPA)
tin            66                  58                        50                        18
aluminum       77                  76                        70                        26
zinc           116                 70                        108                       43
iron           159                 170                       211                       82   
lead           179                 46                        16                        5.6               
gold           185                 180                       78                        27

I poked at this a bit, but the relationship is not immediately obvious to me.