I cannot call myself an expert, but I have the following comments on open-source engines.

There are heaps of open-source free engines in the marketplace now. But if I feel like if you want to learn how game engines work, you still have to build your own one. Because if you download one and poke around in the source code, you won't understand what they are doing, since most of the stuff are very specific, and you won't learn how stuff works without hands-on experience, it takes time though. If you treat the game engine as a black box, it is fine too. However, you probably would end up with a game that is very basic, and when you want to know what specific piece does, you probably get confused. That's my personal feelings about open-source engines.

One thing good though about open-source engines is when you want to incorporate certain feature, or take reference of how certain components of an engine works, that's the way to go...

Yesterday, I wanted to implement the animated skybox, and I want to borrow some ideas from the web, there isn't any source code with it, it's just a pdf, it shows me how to add and multiply materials samples together, I had no idea what that meant, so I looked the unreal engine source code, that's the only place I use open-source engines.

Thanks

Jack

You make some very good points.

2 hours ago, lucky6969b said:

Yesterday, I wanted to implement the animated skybox, and I want to borrow some ideas from the web, there isn't any source code with it

I could be wrong but isn't the idea normally not to provide other developers with the source code; directly like this? It is one of those things we do as developers not to hinder the learning cycle of other developers?

 As receiving the answer is not, the same as finding the answer and game development is all about solving problems.

The main reason for opensource engines, the whole reason we keep making them. It's a way for us to share answers without just directly telling other developers what it is. At least that is how I feel.