[Request] "Region render" for lightmap calc

[anonymous_user_8171b254]

It would be awesome if UE4 had something that worked as a region render so that we would be able to refine lightmaps and test different parameters only at a determined location without having to wait the whole scene calculation.
Even better if this region render could smooth out with the already calculated lightmaps. This way, we would render portions of lightmaps one at a time with different parameters.

P.S.: English is not my main language. Feel free to correct me.

[Jacky]

You can already do this by rescaling the lightmass importance volume to the size you want(except for rendering portions one at a time bit.)

[anonymous_user_8171b254]

Why didn’t I think about Lightmass Importance Volume? Haha
Thank you very much, Jacky.
Anyway, the second line of my suggestion would still be nice to have. It could come as a checkbox “Recalc only inside Lightmass Importance Volume”.

[anonymous_user_8171b254]

Hmmm, actually the Lightmass Importance Volume thing didn’t work. It should consider the contribution of the already calculated lighting to work well. What it is doing is just ignore completely whatever is outside the volume, resulting in a wrong and darker lighting.

[Tim_Hobson]

documentation: CPU Lightmass Global Illumination in Unreal Engine | Unreal Engine 5.3 Documentation

Lightmass emits photons based on the size of the level, so those background meshes will greatly increase the number of photons that need to be emitted, and lighting build times will increase. The Lightmass Importance Volume controls the area that Lightmass emits photons in, allowing you to concentrate it only on the area that needs detailed indirect lighting. Areas outside the importance volume get only one bounce of indirect lighting at a lower quality.

I hope this helps explain it a little better and why you’re seeing lower quality outside of the LMV.

[anonymous_user_8171b254]

Tim Hobson, that it is how it works currently, I know, but I’m suggesting that UE4 could have a way to preserve already calculated stuff and just recalc the portion inside Lightmass Importance Volume. I think it would be as useful as region render is in offline renderers like V-Ray. Currently, if you want to test different lighting parameters, you have to wait 5, 10 or 20 minutes because UE4 will build the lighting for the whooole scene when you actually only needed to see the difference the new parameters will make to a little corner of a wall, for example.

[Gaumzy]

I don’t think light mass importance volume works as region light build. It calculate the entire scene. region light build should be more precise, what we have as light mass importance volume is not that useful. Unreal engine should improving it, this can help lot for improving overall scene quality. I will really appreciate any help on this topic.