Recommended Lightmass Version

Development Rendering
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Hello,

We are currently having a debate internally about using CPU or GPU Lightmass. We are currently using GPU Lightmass, and there was a general understanding that GPU Lightmass was where the development focus for baked lighting would be on Epics side. Since then it’s been brought to our attention that may not longer be the case, and GPU Lightmass doesn’t seem to be getting much development attention anymore.

So, what is the current recommendation for baked lighting? CPU or GPU Lightmass? Can we expect any major updates to either of these systems in the upcoming release versions?

Thanks,

Aidan.

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Hello,

Unfortunately CPU and GPU lightmass have been in maintenance mode for some time and we don’t have plans for any major updates because our focus has been on realtime lighting. If you are considering GPU Lightmass, be aware there is a known issue preventing it from working with CSM https://issues.unrealengine.com/issue/UE\-291212, otherwise we don’t have a general recommendation over which one to use. What the major points of contention in the internal debate?

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Hi Alex,

Thanks for your answer. I’ve got a quick overview from our Team.

Please note: not all of this has been deeply investigated on our end yet, this is just a quick list of initial thoughts on our end.

GPU LM:

+ Should be theoretically faster to bake.

+ Has the community branch which seems fairly active.

+ Better support of emissive materials.

- Inconsistent results

- Reflection Probes don’t always bake properly

- Does not handle multiple lighting scenarios properly

- Lacks controllable settings.

- Doesn’t work well with automation.

- Crashes without information when map check issues are present.

CPU LM:

+ A lot more granular control over settings.

+ Handles multiple lighting scenarios properly.

+ Swarm

+ Works well with automation

- Slower on a single machine.

- May be missing certain features.

- Rect lights don’t seem to work as well on CPU Lightmass.

We’ve generally seen a lot of inconsistencies between the two methods. But GPU Lightmass seems very unreliable, from what I’ve gathered from our team.

Thanks,

Aidan.

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Thanks for the feedback, I’ve passed it along to our team to help prioritize future work in the area.

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I have more issues with CPU LM. I will link my previous post here. I hope this can be resolved in the future: