[ianhawes]

You may be referring to Unreal in this instance. Unreal is open source* but you pay to license the engine, so you can make core changes I.e. memory management or tweak underlying net code. Unity is closed source and so you can only really extend very core parts of the engine.

FWIW my experience in gaming has been that Unity is exceptionally powerful and allows game developers to create games that would otherwise require an entirely separate dev team to support the engine. When I first learned game dev, the code sections were almost entirely devoted to interacting with the underlying graphics libraries (OpenGL or DirectX) and hardly any to creating powerful features in a game. Now, using something like Unreal or Unity is akin to using a web framework like Ruby on Rails or Laravel.

* The source is available to view and modify

[angus-prune]

Unreal is not open source.

I think you might mean that unreal is "source available" which doesn't confer any of the rights of open source, but does allow you to view and modify the source code subject to a commercial license (which might be free for personal, small scale use. I don't know unreal's pricing structure).

[aleph_minus_one]

> Unreal is open source

Unreal is not open source (cf. the Open Source Definition: https://opensource.org/osd/). It's just that the licencee is allowed to view and modify the source code within the limits of the licence.

[Xeamek]

BTW, unity does offer a full source of the engine to companies that are willing to pay enough for it. So you can effectively modify it as much as unreal.

Although, I don't even know if the KSP2 studio is big enough to afford it, let alone if they are actually doing it

[dragonwriter]

> open source*

> * The source is available to view and modify

“source available”, and then you are using common terminology in a non-controversial way and don't need an explanation that is longer than the term.

[protocolture]

My limited experience with Unity was that, if you are planning to do something the Unity way, its very easy to bootstrap and start just coding cool features. Which is why theres a proliferation of Unity store assets + cheap gameplay on steam.

But if you want to do something a bit more complex, like modifying 3d objects in flight based on unit interaction, not only are you fighting an uphill battle, but the documentation is all out of date and mostly wrong. Because Unity isnt just an engine, its a set of default addons to that engine, and each of those addons was written to be just generic enough, but mostly just enable people to start making FPS and RTS games really quick. If you want to step outside that paradigm you are basically just engine coding again.

[squeaky-clean]

Plenty of companies have source access to Unity and write their own custom portions of it. It's just not accessible at the hobbyist or indie budget level. It's one of those "call us for pricing" situations.

[dartos]

No people do rewrite parts of unity for their own games, they just don’t rewrite it all the way down at the c++ level.

I’ve known people who worked on some games where they hand rolled a physics engine in c# instead of using the unity one.