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Author Topic: SCIENCE: Quantifying minecart physics  (Read 21470 times)

Friendstrange

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Re: SCIENCE: Quantifying minecart physics
« Reply #15 on: July 07, 2012, 11:09:30 am »

Dont we have a "How does Minecart" thread?
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expwnent

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Re: SCIENCE: Quantifying minecart physics
« Reply #16 on: July 07, 2012, 11:48:26 am »

Posting to watch.

Dont we have a "How does Minecart" thread?

This looks like it'll be MUCH more detailed and quantitative.
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darkrider2

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Re: SCIENCE: Quantifying minecart physics
« Reply #17 on: July 07, 2012, 02:09:02 pm »

Dont we have a "How does Minecart" thread?
This looks like it'll be MUCH more detailed and quantitative.
I think that thread went off the rails at some point.
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Ivir_Baggins

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Re: SCIENCE: Quantifying minecart physics
« Reply #18 on: July 07, 2012, 02:11:46 pm »

Dont we have a "How does Minecart" thread?
This looks like it'll be MUCH more detailed and quantitative.
I think that thread went off the rails at some point.

Ba-dum TISH
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Snaake

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Re: SCIENCE: Quantifying minecart physics
« Reply #19 on: July 07, 2012, 05:01:56 pm »

Dont we have a "How does Minecart" thread?

I'm fairly certain I mentioned this at some point:   my experiments posted here are inspired by (a few posts in) that thread, but the focus is pretty different.
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krenshala

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Re: SCIENCE: Quantifying minecart physics
« Reply #20 on: July 07, 2012, 05:21:42 pm »

For those wanting to do tables of aligned data, use the {tt} tag (I'm using braces here instead of brackets due to BB code). Its the typewriter looking icon next to subscript in the button selection above the text box for post submission.
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Quote from: Haspen
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Zepave Dawnhogs the Butterfly of Vales the Marsh Titan ... was taken out by a single novice axedwarf and his pet war kitten. Long Live Domas Etasastesh Adilloram, slayer of the snow butterfly!
Doesn't quite have the ring of heroics to it...
Mother: "...and after the evil snow butterfly was defeated, Domas and his kitten lived happily ever after!"
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Snaake

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Re: SCIENCE: Quantifying minecart physics
« Reply #21 on: July 10, 2012, 07:01:58 pm »

...Your conclusions about order are also valid.  For example, do you take the friction value from the tile you started in or finished in?  Do you decrease speed from friction before or after you move?  I believe I have all those things done correctly in the python program, as it exactly matches my experimental observations.   I do have a spreadsheet of raw results if you want to PM me your email address.
...
As far as the initial push, I used the per-tile delay data on the straight track to solve for the unknowns: starting position, starting velocity, and per-tick friction.  I had to try a few different assumptions about order of effects, but eventually it matched exactly.  So the reason for 0.5 is because the numbers fit and it made sense.   (Speculating about DF's internal implementation, it seems positions are tracked as floating point numbers but tiles are defined at integers, so whenever something gets built or placed it probably gets put at an exact spot "in the middle" of the tile )

I'll send you a pm with my email address, but would you mind explaining the basics about the python program (seeing as you already posted the code anyway), or rather, describe the calculation steps (done per tick?), and their order, so others could understand it better too?


So yup, 2nd minecart science fort: 2x16 embark, forested island, right next to some elves, hopefully no goblins (didnít remember to check, but most of the island was inhabited by the elven civ). 2x16 means the embark is a bit under 100 tiles wide, but I now have a N/S tunnel 766 tiles long.

Testing #9-10 (down ramps, ramp friction):
Spoiler (click to show/hide)

Testing #10 (up ramps):
Spoiler (click to show/hide)

I also think itís noteworthy that due to my impatience and lazyness (to disable the push command for the short while dwarves were doing modifications), at least 4 dwarves have received various fractures and at least as many others some bruises (one got hit 3 times because he took so long to carve tracks). One was unlucky enough to get a piece of skull jammed through his brain, and died. SoÖ feather wood minecarts: maybe safer than iron ones, but donít bet on it?

For the next update, I think I'll test how much energy highest rollers give (finishing up #13), then maybe continue with the rest of the roller questions. I think I'll try and split up the SCIENCE into smaller chunks from now on (well, this post is already implementing that idea, but the reasoning for the earlier megaposts is I didn't want to just make a post with all the research questions, then have people wait several days before giving any results).
« Last Edit: July 10, 2012, 07:24:04 pm by Snaake »
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DrKillPatient

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Re: SCIENCE: Quantifying minecart physics
« Reply #22 on: July 10, 2012, 09:11:27 pm »

Here's something perhaps worth investigating, if at some point the tests branch off into physics of creatures in minecarts: if a dwarf swings his melee weapon at an enemy while riding past it in a minecart, will the momentum of the minecart add to the force of the swing? I'd guess that the best way to test this would be with hammers hitting low-weight creatures. If the force of the swing is at all affected, it will likely cause the creature to fly farther. This probably cannot be quantified by injuries to the enemy unless the effect is so extreme as to yield radically different types of wounds.

EDIT: Two more points of interest:
- Can enemies strike at a dwarf in a minecart, and if so, do they suffer any penalty for doing so?
- If a weapon is embedded in a minecart-riding dwarf, will it be yanked out of the wielder's hands and carried along? If not, will it be pulled out of the dwarf by the advance of the minecart?
« Last Edit: July 10, 2012, 09:22:56 pm by DrKillPatient »
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Snaake

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Re: SCIENCE: Quantifying minecart physics
« Reply #23 on: July 11, 2012, 05:36:45 am »

Here's something perhaps worth investigating, if at some point the tests branch off into physics of creatures in minecarts: if a dwarf swings his melee weapon at an enemy while riding past it in a minecart, will the momentum of the minecart add to the force of the swing? I'd guess that the best way to test this would be with hammers hitting low-weight creatures. If the force of the swing is at all affected, it will likely cause the creature to fly farther. This probably cannot be quantified by injuries to the enemy unless the effect is so extreme as to yield radically different types of wounds.

EDIT: Two more points of interest:
- Can enemies strike at a dwarf in a minecart, and if so, do they suffer any penalty for doing so?
- If a weapon is embedded in a minecart-riding dwarf, will it be yanked out of the wielder's hands and carried along? If not, will it be pulled out of the dwarf by the advance of the minecart?

I think it would be difficult to test even with the knockback, since that can be quite random too. I've had cats fly a few tiles, or not fly at all, when getting hit by a cart (of approximately the same speed). That said, cavies/bunnies.would be pretty ideal test subjects I think. And I think we know so little of the exact statistics of combat mechanics and skills (cprrect me if I'm wrong) that figuring out any sort of penalty that might result from the speed would be nigh impossible.

Regarding the other two points, there was an example in the dev logs where a dwarf was riding a cart that was launched through the air and it's flight path passed near a goblin on the ledge. The goblin swung at the dwarf as he passed by, and the dwarf dodged out of the cart and onto the ledge.

Not going to do it any time soon (since I still have several of my original points untested), but I'd probably test this by pitting some the target(s) in a something*3 area, and engineering a cart to pass through the middle (preventing gobbos from getting out somehow - probably easiest just with gaps in the floor).
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WanderingKid

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Re: SCIENCE: Quantifying minecart physics
« Reply #24 on: July 11, 2012, 02:58:53 pm »

Just to add in a little extra data, I believe you're correct that 'highest friction' is roughly infinite.  I currently have a minecart build that gets guided up about 30 z levels and gets pushed back for marble rock movement up to the main smelting area (I've got a ton of coal in this fort).

That cart's return path is simply a series of slopes back down to the pickup zone.  If it's picking up 500 Urists (roughly) per level, it's at (at least) 15,000 Urists when it hits the turn near the bottom (walled for guidance) and then the friction stop.

A way to test this might be to use simple floor friction.  Don't use the track after a certain point and see how far it goes on the floor.  Hm.  My current embark isn't wide enough to try that.

Snaake

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Re: SCIENCE: Quantifying minecart physics
« Reply #25 on: July 11, 2012, 03:14:24 pm »

A way to test this might be to use simple floor friction.  Don't use the track after a certain point and see how far it goes on the floor.  Hm.  My current embark isn't wide enough to try that.

Definitely a good way to test it, once floor friction is known :P. You mentioned that the track stop is after a turn, what about if you move it to right at the bottom of the 30z ramp? Of course, I think we can only call it "effectively infinite" if it's tested on something like a straight set of ramps down a mountain slope and underground all the way to SMR, and a highest track stop there, immediately. That could net something like 300z at least, for about 150 000 Urists. Effectively infinite, since that's the highest-energy setup I can think of that's achievable with regular worldgen (oh, you can add a set of highest rollers at the top I guess, but that's only a couple of thousand Urists more, probably).
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Reese

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Re: SCIENCE: Quantifying minecart physics
« Reply #26 on: July 11, 2012, 03:57:02 pm »

I am so glad people are quantifying these things, I have been having so much trouble figuring this stuff out on my own.

The how does minecart thread was so disappointing and lacking in !!science!!, and the wiki doesn't have much info yet either.
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WanderingKid

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Re: SCIENCE: Quantifying minecart physics
« Reply #27 on: July 11, 2012, 04:02:35 pm »

Definitely a good way to test it, once floor friction is known :P.
I thought earlier in the thread it was tested out at 16 Urists?

Quote
You mentioned that the track stop is after a turn, what about if you move it to right at the bottom of the 30z ramp?
Not in that particular setup, I can't.  I'm relatively sure I'll be making another 'long hauler' cart shaft down to the caverns eventually to bring up random goods, I'll try it then.


Quote
Of course, I think we can only call it "effectively infinite" if it's tested on something like a straight set of ramps down a mountain slope and underground all the way to SMR, and a highest track stop there, immediately. That could net something like 300z at least, for about 150 000 Urists. Effectively infinite, since that's the highest-energy setup I can think of that's achievable with regular worldgen (oh, you can add a set of highest rollers at the top I guess, but that's only a couple of thousand Urists more, probably).
I'm expecting there's a max-Urist speed for minecarts, otherwise they'd eventually catch on fire from air friction.  Though, I have to admit, using that as a weapon into your HFS entry could be hysterical, if you can control it to be a single path outwards.  Clown Smear by Cart.  Joy.

Snaake

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Re: SCIENCE: Quantifying minecart physics
« Reply #28 on: July 11, 2012, 04:54:35 pm »

Definitely a good way to test it, once floor friction is known :P.
I thought earlier in the thread it was tested out at 16 Urists?

That's what I got from one non-repeated test (since it was actually an accident). xmoffit quoted a figure of 20 Urists in the other thread, though, iirc. Something in that range, probably, but the exact mechanics are still less certain.

Quote
I'm expecting there's a max-Urist speed for minecarts, otherwise they'd eventually catch on fire from air friction.  Though, I have to admit, using that as a weapon into your HFS entry could be hysterical, if you can control it to be a single path outwards.  Clown Smear by Cart.  Joy.

I also think it's possible there's a general max speed, hence it's inclusion in "later research."
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Snaake

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#13-14, plus bonus question
« Reply #29 on: July 12, 2012, 04:52:22 pm »

#13-14:[/u]
Spoiler (click to show/hide)

tl;dr version: Posting some results now: Highest rollers are 1250 Urists (I think; see the full text), as per my previous guess. Having several 1-tile rollers just gives the same speed as with only one 1-tile roller. Longer rollers not yet tested.

Started testing a new question: how much energy does a minecart need to skip over a 1-tile "open space" channel? Answers so far:
p=.== or R.== both work, that is to say, if a dwarf pushes (the p) a cart, it needs to have 1 tile between the channel and the hauling stop with the push, but if rollers are used, the gap can be adjacent. Testing for energy required is ongoing (didn't have time to play today, just writing up what results I got yesterday evening).
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