Determine when the game is falling back to not using Lumen GI

Gonzalo Ferretti
Thu, 05 Sep 2024 17:48:27 +0000
Rendering

Hi there!

Our game has Lumen with Software Ray Tracing, and we are using Lumen GI to do the heavy lifting of the final visual result.
We are having an issue with some of our users that report that our game looks as if the lights were turned off. These users are all integrated graphics users, and we’ve validated on our own machines that integrated graphics result in Lumen GI not working. We’ve found that if we compare our levels when Lumen GI stops working AND overriding Global Illumination in a Post Process Volume with “None”, the results are identical. So, it seems that Unreal is falling back to turning off GI whenever an iGPU is used. We are trying show the user a prompt if this is the case, so the user knows what to expect if they open the game with an unsupported GPU. However, even after combing through the engine’s code, I haven’t been able to find a clear sign of when this fallback is happening, to be able to detect it a the beginning of the game.

Are there any C++ accessible signs to tell when this is the case? Is there something I’m missing here?

6 posts - 4 participants