A technical analysis of the graphics rendering in Cities: Skylines 2 has identified the reason why the performance is just so poor. Put simply, the game is trying to draw the cityscapes using a shocking number of polygons, with few systems in place to reduce the amount when it's not needed. It's not something that should be happening in a modern game but the recent breakdown also suggests changes within Unity are partly to blame, too.
Before the game even came out, developer Colossal Order issued a warning to potential customers that the performance of Cities: Skylines 2 had «not achieved the benchmark we targeted.»
And when the city management sequel finally appeared, it turned out the dev wasn't kidding and the only way to get any semblance of a decent frame rate was to whack most of the graphics settings down to low or completely off. The first patch for the game helped matters a bit but the fact remains that, as a simulation-management game, it really shouldn't be as GPU-dependent as it is.
I learned the full answer to that puzzle over the weekend, via a short Reddit post. It contains two things: A link to a technical analysis of the game, involving a spot of decompiling and rendering software tools, and an excellent discussion of the findings. The breakdown was carried out by software developer Paavo Huhtala, who explored the game's inner workings with a fine toothcomb.
It's a long and dense read, especially if you don't know much about rendering, but the primary issue is that the cityscapes are being drawn using way too many polygons. And I mean by multiple orders of magnitude too many. How do 25,000 vertices (corners of a triangle) sound for a simple clothesline model?
If you need a point of reference, take the
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