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Be like the Romans - make them all straight lines :-)

Of course the Romans didn't give a shit who's property rights they might be violating. I live in Lincolnshire UK, where Roman roads are still used. The last one that got changed was years ago when they had to put a kink in Ermine Street (now the A15) at RAF Scampton when they extended the runway to accommodate Vulcan bombers.

In my area, streets are often church tower to church tower. From the middle ages. You can nowadays drive these streets and the middle line indicators align perfectly with the church tower showing up. I think the church /church based government share that property right understanding of the Romans :)
The romans did care about property lines! Romes’ second aqueduct was held up when land owner Crassus refused to give up private land for its construction. Check out the article for a fascinating read: https://en.wikipedia.org/wiki/Roman_aqueduct
The tech seems really cool, but the road showed in the examples is not any less insane, like, why?
Another aspect of these games is the subtle scale issues that aren’t readily apparent - even the newest biggest city simulators are fractions of the size of a real city.

Road and rail curves are massive and it’s hard to understand just how big they are without having to actually walking them.

I love SimCity 2000 and these roads look really cool but I'd really like to see a city-builder go in a different direction.

One of the biggest problems with North American cities is their endless, car-centric suburban sprawl. SimCity games may be really fun to play but they seem to reinforce this problem and anyone who grows up playing them will not learn about alternatives for more livable cities.

New Urbanism, traditional neighbourhood design, streetcar suburbs, one-way streets, bike paths, walking paths, mixed-zone walkable villages (light commercial with residential), smaller single-family houses and duplexes, triplexes, houses behind houses. Many of these are older and more traditional techniques to yield higher density neighbourhoods without building up to large apartment buildings.

It would be really cool to see a game that focused more on creating these kinds of realistic and aspirational living spaces instead of the usual cookie-cutter suburbs linked up by huge roads and a large downtown core.

I was fascinated by them since reading a guide for Cities: Skylines that said that roads were like trees. There's a trunk that moves large amounts of nutrients and little branches that distribute the nutrients to the leaves. Such simple rules, but such complex and deterministic results.
One game that had a different perspective (first person mmo), but a fun network of road building in a simulated wilderness .. Wurm Online
Cool shit!

> Do 99% of city-builder players care what shape the corner radius of the intersection has? Most likely, no.

Maybe not... but out of all the players who care corner radius of roads in games, 99% of them probably are into city-builder!

Articles like these are the reason I continue to check hackernews.

Author please keep writing.

There's so many things in games that are taken for granted at play time but which actually take a lot of thinking and work to get right. Roads for instance aren't something which your typical player will look too closely at... but they will notice if they look or behave in a way that seems wrong.

I've been playing Kingdom Come 2 of late, and I find it's natural to just kind of take the world they've created for granted - just like we do the real world. But when you actually stop and look you have to consider that every one of the finely crafted details was built by someone's sweat and tears, be it artists, programmers, or designers at edit time.

No wonder it's an industry of crunch, the work involved can be uniquely daunting.

Ah yeah, this is actually part of why I never complete games.. I spend so much time messing around looking at all the cool little details, exploring the environment and generally "experiencing the place" moreso that pursuing game mechanics or completing levels/quests/etc. ... some of my favorite games, I've played probably like 1/4 of lol
My version of OP's roads problem is blob autotiling - how tiles connect to their neighbors. 256 possible neighbor combinations reduce to 47 valid patterns once you realize corners only matter when both adjacent edges are present. You paint a semantic type like "wall", the system resolves the right tile from those 47 patterns - but painting one tile cascades outward, neighbors re-resolve, which triggers their neighbors, and you're tracking stale state to keep it all consistent. Same underlying problem as road segments affecting connected intersections.

I've been trying to make this as easy as possible for non technical people to draw terrain in craftmygame (the game engine I'm building) here's what the terrain painting looks like in the editor so far : https://youtu.be/bFrUYM2t3ZA?si=tw1LqBWR7Uyn08lR&t=37

I studied urban planning back in the university and one of the classes was road design. Though I forgot most, one part of the class was about how to design roads with curves that's safe for cars. This post just brought that memory back to me.
This is a really interesting approach but I'm curious to see how it translates to the actual mesh extrusion, or whatever 3d technique they adopt. It's relatively easy to do this in 2d, it's the 3d solution that accommodates terrain variation that introduces the real explosion of complexity
The author might get a kick out of an upcoming game called Junxions, which is a sandbox game to just do that... create road junctions.

The subreddit is here: https://www.reddit.com/r/Junxions/

Sure they teased that they've made their own solution, but I think Junxions should scratch the itch of most of us here interested in this kind of game.

Everyone is raving about this article. It feels so much like a tease to me. Maybe I'm just impatient idk.
> And they are also… a math nightmare. Differential geometry. Integrals. Oh my… Which is probably why most games don’t even dare.

Wonder if cubic parabola (used by some railways, and visually near indistinguishable from clothoid) has easier maths.

Ahhh.. this is a writer after my own heart. Absolutely brilliant write-up. I had the same obsession with roads, from SimCity onward; they're the circulatory system of any city, and never in the history of cities or the history of circulatory systems have the vessels been straight lines. The streets of a European or Asian village usually tell a story about how roads were built over the fastest footpath from the outskirts to the center, then over time amended to go around some buildings that were built in the way. Whereas roads in rural parts where I come from run in long straight lines and then suddenly swerve to get around a piece of land that a farmer wouldn't sell. But grids only exist in some parts of the few cities that were built mostly by colonial powers, or developed later with master planning. And even those grids usually split from their original orientation to becoming north-south at some point in in the city's development, leading to the interesting downtown triangle blocks of cities like Portland, San Francisco, Los Angeles, Seattle, New York. Other cities started to grid around their core footpath villages, like Madrid, Barcelona.

The cities I find the most interesting (for roads) are the ones which kept gridding out in new directions to follow the course of a river. Cities like Buenos Aires, New Orleans, and Saigon, where the original paths followed curves around the river bends, resulting in multiple intersecting grids.

The intersections and division boulevards between grids are, of course, the most beautiful and architecturally interesting parts of any city. They are where the blocks are strangely shaped and the buildings can't be rectangular, and usually where every inch of land is at a premium as well. It would be nice if a city-builder could simulate that aspect of urban growth: The shift from village center to grid, and old grid to new grid.

Can relate the fascination with roads I use to like drawing them loads as a kid. I find Satisfactory the most satisfying for building transport systems (and building generally) your work incorporated into a mod for that would be really cool.
The bit about the clothoid finally made me understand the odd shape of highway junctions. I always wondered why they want me to enter turns fast and then slow down progressively until the turn becomes a new straight. Unfortunately sometimes that straight is the highway, and they should give us plenty of space to build up speed and match the traffic inside the highway. Sometimes they do, sometimes they don't.
[Adds “clothoid” to vocabulary]
"Do 99% of city-builder players care what shape the corner radius of the intersection has? Most likely, no."

Finally, I am part of the 1%!

> I think roads lie at the heart of every city builder. It’s the fabric on which cities are built.

To paraphrase the article, this is what urban planners have nightmares about. Roads (as in: things made for cars) aren't the fabric of a city, streets (as in: things made not only for cars, but also for pedestrians, cyclists, public transport etc.) are. See also: https://en.wikipedia.org/wiki/Stroad

Always thought some streets in city builders just are a bit tooooo off :D

Very nice article - good read !