> The fact that it's open source is also big, because there are often bugs in the Unity engine that I can't fix since I don't have source access.

And very bad ones, at that; which will persist for years and several major versions.

For instance: let's say you have a game that supports user generated content via loading asset bundles. This being the lowest barrier to entry for games to leverage the unity editor for UGC, it's quite common.

Well, now and always, and known and reported since at least 5.2, any asset bundle that references a class not found in the compiled game client will crash the client on load.

The only work around is to write your own asset bundle inspector and pre-analyse on load.

I know quite a few game devs (side-effect of both living in Malmö and being active on the TiGsource forums) and if there is one common thing I hear about Unity it's how it does not seem to care at all about backwards compatibility, and how upgrades can completely screw over projects.

I don't know what the story is with Godot (beyond the breaking changes between 2.0 and 3.0 that was mentioned in the linked blog post) but if that is a lot better then I can imagine that some game devs might be more interested in Godot for that reason too.

Every version change, even minor revisions, come with a real risk of breaking your compiled asset bundles. From shaders to light maps to referenced classes. It's a huge amount of effort to keep a project tracking Unity version upgrades.

What do people do to deal with it? Are there services / libs that help you do the conversion?

Or is it that you can't fully trust them, and you'll need to do that by hand anyway, because you might be one of the exceptional cases?

From my limited experience, download the version that it was made with. Unity has a list of older versions right in it's hub.

What's funny is I think all of the major game studios that I know of essentially lock game engine per project once they're coding along. It's just expected that you stick with it for the rest of the project. Maybe 1 upgrade mid project. I had heard bungie used to, in the halo days, lock the engine 8-11 months out and the core tech team started working on the next game. The AAA studio I worked for essentially did that 3-6 months out.

But those were 2-3 year game cycles. Maintaining a project would be less fun. But it'd be like choosing to do a rails or react upgrade.

Yikes. Does Unity do forced paid upgrades, so you'd have to deal with the incompatibilities?

Do they have a culture of incompatibilities so they can simplify their development and keep the best features and discard the worst?

Unity is both free and subscription based.

They make older versions of the engine available in their management app, and projects are linked to a specific version unless you explicitly upgrade.

I wonder why this discussion always falls to Unity and Godot; Unity source is not available, while Unreal Engine source is.

Unreal also has more features available than both engines out of the box, as far as I am aware. I don't want to sound like an advert, but the shading and Blueprint systems in UE4 are extremely intuitive and easy to work with, and the C++ is definitely managable. I've never used Godot, but the last time I compared Unity to UE4 it felt extremely clunky. Lastly, prototyping stuff in UE4 is fun, once you get used to it and develop your own workflow.

Last time I checked, the 2D features of Unreal were abandoned. Godot and Unity have both very nice 2D features and I would say that 2D is simply more manageable for a small indie game by a single developer.

The core benefit of unity over unreal is that it has community momentum. There are more tutorials, documentation and things available in their store. I prefer unreal myself, but those are things that are hard to combat against without epic making a more conscious effort.

History I expect, Unreal was a expensive closed engine for AAA games for something like 15 years before moving to a source provided model where you paid with revenue. Unity had a free tier for something like 10 out of those 15 years.