Is there a good open source game engine for learning how game engines work?

Question

So I've been wondering about this for a while. And been considering different options like torque 3D. Any helps appreciated.

Answer 1

https://www.sololearn.com/discuss/448721/?ref=app
https://www.sololearn.com/discuss/498964/?ref=app
https://www.sololearn.com/discuss/708938/?ref=app
https://www.sololearn.com/discuss/488976/?ref=app
https://www.sololearn.com/discuss/938441/?ref=app
https://www.sololearn.com/discuss/708962/?ref=app
https://www.sololearn.com/discuss/1167480/?ref=app
https://www.sololearn.com/discuss/625747/?ref=app
https://www.sololearn.com/discuss/620013/?ref=app
https://www.sololearn.com/discuss/882863/?ref=app
https://www.sololearn.com/discuss/761432/?ref=app
https://www.sololearn.com/discuss/1164434/?ref=app
https://www.sololearn.com/discuss/622803/?ref=app

Answer 2

Both Godot and Unreal Engine are open source. Don't know about Godot but in case of Unreal the source code is in a private repo on github which you get access to after joining unreal engine's organization.

Answer 3

Id tech engines are open source and are very simple, games like Half Life, Half Life 2, Counter Strike, CSGO, Call of Duty are based off those engines.