[Ed. note: While we take some time to rest up over the holidays and prepare for next year, we are re-publishing our top ten posts for the year. This is our number one post of 2021! Thanks for reading and we’ll see you in the new year. ]
Dwarf Fortress is a kind of oddball ardour initiatives that’s damaged into Web consciousness. It’s a free recreation the place you play both an adventurer or a fortress stuffed with dwarves in a randomly generated fantasy world. The simulation runs deep, with new video games creating a number of civilizations with histories, mythologies, and artifacts.
It has change into infamous, and rightly so. Particular person dwarves have emotional states, favourite gems, and grudges. And all of it takes place in an ASCII interface that appears imposing to newbies, however feels just like the textual content crawl in The Matrix: craftsdwarf, river, legendary megabeast.
The whole recreation is product of 1 developer, Tarn Adams, aka Toady One, who has been engaged on Dwarf Fortress since 2002. For the primary 4 years it was a component time venture, however since 2006 it’s been full time. He writes all of the code himself, though his brother helps out with design and creates tales based mostly on the sport. Up till now, he’s relied on donations to maintain him going, however he’s presently engaged on a model with pixel graphics and a revamped UI that will probably be out there for buy on Steam.
I reached out to Tarn Adams to see how he’s managed a single, rising codebase over 15+ years, the perils of pathing, and debugging lifeless cats. Our dialog beneath has been edited for readability. In order for you extra, we additionally spoke with Tarn on the podcast.
Q: What programming languages and different applied sciences do you utilize? Principally, what’s your stack? Has that modified over the 15-20 years you’ve been doing this?
A: DF is a few mixture of C and C++, not in some form of commonplace obeying means, however kind of a large number that’s accreted over time. I’ve been utilizing Microsoft Visible Studio since MSVC 6, although now I’m on some model of Visible Studio Neighborhood.
I take advantage of OpenGL and SDL to deal with the engine issues. We went with these as a result of it was simpler to port them to OSX and Linux, although I nonetheless wasn’t ready to do this myself after all. I’m unsure if I’d use one thing like Unity or Unreal now if I had the selection since I don’t know the right way to use both of them. However dealing with your personal engine can also be an actual ache, particularly now that I’m doing one thing past textual content graphics. I take advantage of FMOD for sound.
All of this has been fixed over the course of the venture, besides that SDL received launched just a few years in so we may do the ports. On the mechanical facet of the sport, I don’t use a whole lot of outdoors libraries, however I’ve occasional picked up some random quantity gen stuff—I put in a Mersenne Twister an extended whereas in the past, and most lately I adopted SplitMix64, which was featured in a chat on the final Roguelike Celebration.
Q: What are the challenges in growing a single venture for thus lengthy? Do you suppose that is simpler to do by your self? That’s, since you wrote each line, is it simpler to take care of and alter?
A: It’s simple to overlook stuff! Trying to find ‘;’, which is a free methodology however shut sufficient, we’re as much as 711,000 traces, so it’s simply not potential to maintain all of it in my head now. I attempt to identify my variables and objects persistently and memorably, and I go away sufficient comments round to remind myself of what’s happening once I arrive at a spot of code. Generally it takes a number of searches to search out the precise thread I’m making an attempt to tug on once I go and revisit some piece of the sport I haven’t touched for a decade, which occurs fairly a bit. I’d say most modifications are targeted solely on sure components of the sport, so there may be form of an lively molten core that I’ve a a lot better working data of. There are just a few actually crusty bits that I haven’t checked out since earlier than the primary launch in 2006.
Concerning the relative ease of doing issues on my own, actually for me, who has no expertise engaged on a big multi-person venture, that is the best way to go! Individuals clearly get good at doing it the opposite means, for instance over within the AAA video games context, and clearly a number of engineers are wanted over there to get issues finished on time. I’d be hesitant to say I can go in and alter stuff sooner than they’ll, essentially, since I haven’t labored in that context earlier than, but it surely’s true that I don’t have any team-oriented or bureaucratic hurdles to leap via once I need to make an alteration. I can simply go do it. However I additionally should do it alone.
Q: What’s the most important refactor/change that you simply needed to make?
A: There have been some refactors which have lasted for months, redoing sure knowledge constructions and so forth, although I’m unsure something is ever a refactor strictly right here since there’s at all times alternatives to push the mechanics ahead concurrently and it is sensible to take action when the code data is recent.
Including the Z coordinate to make the sport mechanically 3D (whereas nonetheless being textual content) was one other one, and actually essentially the most mind-numbing factor I’ve in all probability ever finished. Simply weeks and weeks and weeks of taking logic and performance calls that relied on X and Y and seeing how a Z matches in there.
Making the merchandise system polymorphic was in the end a mistake, however that was an enormous one.
Q: Why was this was a mistake?
A: Once you declare a category that’s a form of merchandise, it locks you into that construction far more tightly than in the event you simply have member parts. It’s good to have the ability to use digital capabilities and that form of factor, however the tradeoffs are simply an excessive amount of. I began utilizing a “device” merchandise within the hierarchy, which began to get varied performance, and may now assist something from a stepladder to a beehive to a mortar (and pestle, individually, ha ha), and it simply feels extra versatile, and I want each crafted merchandise within the recreation had been underneath that umbrella.
We do a whole lot of procedural era, and if we wished to, say, generate an merchandise that acts partially like one factor and partially like one other, it’s simply means tougher to do this if you end up locked down in a category hierarchy. Including issues like diamond dependencies and all that simply find yourself tying you in knots when there are cleaner methods to do it. If totally different elements can simply be turned on and off, it’s simpler, and lets you do extra.
I believe some recreation builders discuss with this as an entity element system, although it’s my understanding that harder-core optimizer individuals consider that as one thing else the place you’re really breaking issues down by particular person fields. Utilizing a single object with totally different allotted subobjects is nearly actually worse for cache misses, which is a complete different factor, however the advantages in group, flexibility, and extensibility simply can’t be ignored, and the totally different subfields of the device merchandise aren’t used so typically that it turns into an optimization difficulty.
Q: Did you run into any points transferring from 32 bit to 64 bit? That seems like a kind of issues that was large on the time however has change into fairly accepted.
A: By no means! I’m struggling to consider a single difficulty. Fortuitously for us, we already had our byte sizes underneath management fairly nicely, because it comes up saving and loading the worlds; the format wanted to be nailed down again once we set that up, particularly as a result of we’ve needed to cope with endian stuff between OSes and all that. And we don’t do any gnarly pointer operations or different stuff that may have gotten us in bother. It simply ended up being actually good code for 64 bit conversion as a consequence of our different practices, fully by chance. The primary difficulty was simply getting the time collectively to make the change, after which it didn’t find yourself taking practically so long as I assumed it might.
Q: I’ve seen different video games much like DF die on their pathfinding algorithms.What do you utilize and the way do you retain it environment friendly?
A: Yeah, the bottom algorithm is just a part of it. We use A*, which is quick after all, but it surely’s not ok by itself. We are able to’t benefit from among the improvements on that (e.g. jump point) since our map modifications a lot. Usually, individuals have used approaches that add varied bigger constructions on high of the map to chop corners, and due to the altering map, these simply take too lengthy to take care of, or are in any other case a trouble. So our method has been to simply preserve observe of linked elements reachable by strolling. These are fairly simple to replace even when the map modifications rapidly, although it does contain some flood-filling. For example, if water cuts the fortress in half, it must flood out from one facet and replace a complete half of the fortress to a brand new index, however as soon as that’s finished, it’s good, usually. Then that permits us to chop virtually all failed A* calls from the sport—our brokers simply want to question element numbers, and if the element numbers are the identical, they know the decision will succeed.
It’s quick to take care of, however the draw back is that the element indices are maintained for strolling solely. Because of this flying creatures, for example, don’t have world pathfinding intelligence that’s any totally different from a walker. In fight and some different conditions, we use short-range flood fills with their precise logic to provide them some benefits although. But it surely’s not perfect for them.
I’m unsure we’ll try different constructions right here to make it work any higher. For our map sizes, they’ve all failed, together with some outdoors makes an attempt. After all, it could be potential with a very concerted effort, and I’ve seen different video games which have managed, for example, some rectangular overlays and so forth that appear promising, however I’m unsure how risky or giant their maps had been.
The most straightforward concept would simply be one thing like including a brand new index for fliers, however that’s a big reminiscence and pace hit, since we’d want to take care of two indices without delay, and one is dangerous sufficient. Extra particular overlays can observe their pathing properties (and you then path via the overlays as an alternative of the tiles), however they’re exhausting and gradual to take care of because the map modifications. There are numerous different concepts floating round, like monitoring stairs, or doing a little restricted path caching, and there are in all probability some positive aspects to be made there. We’re actually on the fringe of what we are able to presently assist when it comes to brokers and map complexity, so one thing’ll have to provide if we need to get extra out of it.
Q: On that word, you’re simulating a whole lot of issues abruptly—how do you handle so many so many actors asynchronously (or do you)?
A: If we’re speaking about asynchronous as in multithreading, then no, we don’t do any of that, apart from the graphical show itself. There’s a whole lot of promise right here, even with microthreading, which the group has helped me out with, however I haven’t had time to dive into. I don’t have any expertise and it’s a bug-prone factor.
Q: Have you ever tried different initiatives/applied sciences alongside DF?
A: Positive! The facet venture folder that’s migrated between computer systems for the final ten years or so has about 90 initiatives in it. A few of them lasted for days, some for a number of years. They’re principally different video games, virtually at all times in different genres, however there are additionally just a few DF helper initiatives, like the parable generator prototype. Nothing near seeing the sunshine of day, but it surely’s enjoyable to mess around.
Q: Together with your ~90 facet initiatives, have you ever explored some other programming languages? In that case, any favorites?
A: Ha ha, nope! I’m extra of a noodler over on the design facet, somewhat than with the tech. I’m certain some issues would actually pace up the belief of my designs although, so I ought to in all probability not less than study some scripting and mess around with threading extra. Individuals have even been type sufficient to provide some libraries and issues to assist on the market, but it surely’s simply troublesome to dam facet venture trip for tech studying when my facet venture time is for stress-free.
Q: You’ve essentially the most fascinating launch notes. What’s your favourite bug and what triggered it?
A: It’s in all probability boring for me to say, however I simply can’t beat the drunken cat bug. There’ve been just a few movies made about it by this level. That was the one the place the cats had been exhibiting up lifeless everywhere in the tavern flooring, and it turned out they had been ingesting spilled alcohol after they cleaned their paws. One quantity was off within the ingest-while-cleaning code, and it despatched them via all of the signs of alcohol poisoning (which we added once we spruced up venomous creatures.)
If you wish to attempt Dwarf Fortress for your self, you possibly can download it from their website.