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[Aachen]

Moreover, once we define the mixture of, say, vinegar and sulfuric acid, how does that new liquid interact with ammonia?

[Draco18s]

Moreover, once we define the mixture of, say, vinegar and sulfuric acid, how does that new liquid interact with ammonia?

Indeed.

[King Mir]

A horizontal boundary would make a good default action. That does mean you need multiple liquids in a tile, and code to make liquid swap places if a dense liquid is a z-level above a light liquid, and for a liquid to spread out on top of another it the two are adjacent.

Forming a vertical boundary only makes sense for powders. That is something you want, but powders behave differently in other ways, so you do want a different system for them anyway. For instance, you want to have ramps of sand.

[Putnam]

Moreover, once we define the mixture of, say, vinegar and sulfuric acid, how does that new liquid interact with ammonia?

Full simulation of chemical reactions at the atomic level, of course!

Ain't it obvious?

[harborpirate]

Some possibilities:
1. The two fluids block each other from flowing as if they had run into a solid.
2. DF is updated to track multiple liquids in a given tile and the tile gets about half of each. (3 of one and 4 of the other).
3. Both tiles form a default compound, like "sludge" or somesuch.

And those would have to be coded in the RAWs as well.  Very very VERY (if any) few liquid interactions in the real world do 1 (form a vertical boundary).  Most will either mix (3ish*) or layer on top of each other based on density (2).  2, however, is very easy to code, as it can be implied based on the material definitions.  3is is harder, but possible as it depends on what type of material each is (a water-soluable liquid won't mix with a lipid-soluable liquid, even if both are the same density).

It's the acid/base, water/magma type reactions that are extremely difficult to code as every liquid likely interacts in some way to large numbers of every other liquid.  I.e. vinegar and ammonia would both (in large quantities) turn magma into obsidian.

The trickies reactions of all are the ones that involve three or more liquids.  I.e. one is a catalyst for a chemical reaction of the other two (I do not know of any that exist in pure liquid states).

*By which I mean two liquids mixing homogeonously into a "new" liquid.  I.e. water and milk.

Keep in mind that I'm only talking about the default reaction, when a reaction is not explicitly defined in the RAWs. The point is to support lots of liquids without having to define hundreds or thousands of interactions in the RAWs.

There is a fourth option for default reaction that I didn't think of until later:
Swap these two tiles.
If two liquid types with no defined reaction to each other interacted, you'd end up with a pool of "mixed" liquids, but each individual tile would only contain a single type. This would also make the interaction of 2 or more liquids a snap (it would just work automatically), and it would simulate pollution pretty well.

Example (Oil=o, Water=w)

Spoiler (click to show/hide)

wwooo
wwooo
wwooo

wowoo
wowoo
wowoo

owowo
owowo
owowo

I doubt #2 will be easy to code. The game is not set up to handle multiple liquids in a single tile - the game would likely need a new data structure and it could get ugly (especially in regards to performance) when more than just 2 liquids interact. Could be a real CPU hog.

As for #3, the "sludge option", my assumption was that if it was the default to create sludge, most things interacting with sludge would just form more sludge. So you don't have to worry about whether things without defined reactions mix, because they'll just turn into sludge. You could always define how some material reacts with sludge, which would apply no matter what previous interaction created the sludge in the first place. Not very realistic, but easy.

Let me give a little more detail about why I'm advocating the options that I am: I'd like to see other liquids get into the game soon. Pie-in-the-sky perfection takes forever. If we can get something interesting and useful that requires 80% less effort, I'd like to see Toady go for that.

To be honest I think the default of "swap tiles" would be the best default option. You could end up with lakes that were part oil, part water, part whatever; all without doing heavy modifications to the game. Meanwhile, modders could go crazy defining every possible interaction to satisfy the desire for more detail.

[knutor]

I'm not so sure I'm prepared to replay a 4x4 embark region entirely engulfed in miasma because I broke a catastrophic aquifer.  At least not just yet.  Not until I can embark with a space suit for my hunting dog.  Ha!

Sincerely,
Knutor

[Draco18s]

As for #3, the "sludge option", my assumption was that if it was the default to create sludge, most things interacting with sludge would just form more sludge. So you don't have to worry about whether things without defined reactions mix, because they'll just turn into sludge. You could always define how some material reacts with sludge, which would apply no matter what previous interaction created the sludge in the first place. Not very realistic, but easy.

1/7 blood meets ocean.

Ocean becomes sludge.

[harborpirate]

As for #3, the "sludge option", my assumption was that if it was the default to create sludge, most things interacting with sludge would just form more sludge. So you don't have to worry about whether things without defined reactions mix, because they'll just turn into sludge. You could always define how some material reacts with sludge, which would apply no matter what previous interaction created the sludge in the first place. Not very realistic, but easy.

1/7 blood meets ocean.

Ocean becomes sludge.

Good point, another one of the reasons #3 is problematic.

[harborpirate]

The more I think about option #4, "swap tiles when no reaction is defined", the more positives I see for it.

When tiles full of different liquids are on multiple z levels, the denser of the two could be swapped to the bottom (again as the default, when no reaction is defined).

It also allows reactions to continue to take place in the presence of inert substances.

Here's an example of Ammonia, Vinegar, and Water (and Foam representing ammonium acetate).

Spoiler (click to show/hide)

This uses a very simple left to right non match replace method for the default reaction (which I wouldn't recommend for implementation, but works here since its easy to follow). For the purpose of this example, the only defined reaction that we're concerned with is A+V=F.
AAWWVV

AWAVWV

WAFFVW

AWFVFW

WAVFFW

WFFFFW

[antymattar]

As for #3, the "sludge option", my assumption was that if it was the default to create sludge, most things interacting with sludge would just form more sludge. So you don't have to worry about whether things without defined reactions mix, because they'll just turn into sludge. You could always define how some material reacts with sludge, which would apply no matter what previous interaction created the sludge in the first place. Not very realistic, but easy.

1/7 blood meets ocean.

Ocean becomes sludge.

Not true. If you remember what I mentioned before, I said that water would be the purification liquid. Anything that is in water can "somehow" be purified by letting it flow (Ie, dumping it in a river). The sludge would eventually turn back into water if propper actions are taken. If not then it will probably evaporate.

Moreover, once we define the mixture of, say, vinegar and sulfuric acid, how does that new liquid interact with ammonia?

Full simulation of chemical reactions at the atomic level, of course!

Ain't it obvious?

Not quite. What I am saying is that if this system is built in then yes, someone MIGHT actually make something close to a full set chemical reactions for all sorts of fluid. As of now all we need is for alcochol, milk, blood, booze, vomit and oil(rock nut) to be in game. I dint see what is it with people trying to suggest ammonia and make it realistic to combine phosphorous with hypercooled liquid hidrogen to create gems of hydrofosphate or something other :p.

[King Mir]

With the horizontal swapping, what would you do if the liquids were at different levels? Like you have a shallow reservoir of oil, and open a floodgate of 7/7 water at the side. With naive horizontal swapping you'd end up with a few towers of 7/7 water scattered is a pool of 1/7 oil. Similarly vertically swapping 1/7 tile of water with a 7/7 tile of oil would be strange. And a potential water pumping exploit, though not much different from pistons.

[alfie275]

I doubt we'll be seeing stuff like this till multithreading.

[harborpirate]

The simplest way to deal with non full tiles is to cause it to try to combine with the tile directly away from where the interaction is taking place. This does raise the issue of what to do in the case where it cannot combine though.
The effect in game of this proposed answer to your example would be that the full water tiles would push a building wave of oil in front until only full oil tiles remained, which would then start to intermingle with the water.

[King Mir]

Given how pressure works in DF, it wouldn't be easy to make water push other liquids. So you may as well do it right and layer them.

[antymattar]

Did you guys like totally not even read what I just said?

Anyway, tile swaping IS a dumb idea. One tile can have 7 units of ANY kind of liquid at once. Dont you understand. This means that the tiles dont have to "swap", the water and oil can just mix on a tile basis. They wont create a new liquid but they will mix in one tile. the 7/7 water will go over the 1/7 tiles of oil and the oil will be on the top.