1 HN user recommended this demo1 month2015–2016score 1.5
Years with an HN recommendation, 2007–2026
HN cites it as a favorite demo of live coding and hot reload in a game engine.
A GameTrailers walkthrough from E3 2012 of an Unreal Engine 4 real-time tech demo with Epic's Alan Willard. It shows live code changes and hot reloading while the game runs.
This is my favorite Unreal 4 demo - [this video] (sadly missing the wonderful quote "I light my level by dropping a sun in.") I'm completely in awe of the feedback loop here. It even compiles and swaps code while you're in the game!
Unreal 4 demo with live code swapping while in game.
A few years ago (2012) I was taken aback by the Unreal Engine development process. Their IDE features a running game with all elements being selectable and interactively editable. In one video fragment [1] they hop to Visual Studio where they change gravity. After a few seconds of compilation, the game's code is updated. [1] [this video]
Shows changing gravity in Visual Studio with hot reload.
I believe that on Unreal Engine 4, you use C++ and it does have a feature that mimics "live coding" where it recompiles and hot-reload your game even while playing. edit: here it is [this video] (jump to 9:40 if it doesn't load at this point automatically)
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