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Comment by martindevans | Hacker News Reader

Space Engineers isn't made in Unity, it uses their Custom VRAGE engine.

Unity can do far better graphics than KSP has e.g. https://unity3d.com/pages/adam. The fact that there are numerous mods which vastly improve the graphics of KSP is pretty good evidence of this!

Where Unity can be blamed for KSP problems is the constant stutters due to GC - Unity uses an ancient garbage collector. Hopefully that's going to get better soon - apparently there was some licensing problem keeping Unity on an ancient version of Mono, now that MS own Xamarin that's probably not a problem.

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The parent said it's 'not graphics' that's the problem. I agree that it's not really the graphics that are an issue in KSP, but most likely the physics engine.

Essentially, most (unity) games don't allow their users to create content, whereas the essential part of KSP is the creation and simulation of lots of bodies.

I've definitely experienced a substantial slowdown when many entities are on the screen at the same time.

I'm not sure if KSP makes use of the normal Unity physics engine, a third-party one, or something developed in-house.

When they were on Unity 4, they were using Unity's physics engine - that made the game perform badly for bigger constructions (e.g. large rockets, or space stations), because the physics engine was single-threaded and the game is CPU-bound on physics. After switching to Unity 5, things got better. I haven't been up to date with KSP for the past year, so I don't know if they switched to some other physics engine (though I highly doubt it).

Unity uses a modified version of PhysX. Unity 5 updated to a newer PhysX build that supports at least some multithreading.

It sure does fire up more threads, but the performance boost wasn't really all that great (the 4 -> 5 transition increased the amount of parts I could handle by about 2x on my 5820k (6 core)).

I wrote this elsewhere recently on HN but if you also suffer from GC stuttering, there's a nice little mod called MemGraph[0] which lets you tweak some GC parameters. It definitely made a world of difference on my system with lots of RAM.

[0]http://forum.kerbalspaceprogram.com/index.php?/topic/139128-...

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