Hello,
Like you can see in the title, when i try to build the light my entire PC freeze and it’s a real problem because i can’t have a final result and make my pc slower, i don’t think that can be come from my PC but i’ll give you my spec :
CPU : AMD Ryzen 5 1700X , OC 3.80 GHz
GPU : GIGABYTES GeForce 1060 , 6 Go
MEMORY : G.Skill 2x8 Go, 3000 MHz , CAS 14 , Samsung
Unreal Engine 4.21
Hope someone will help me, i can’t use this beautiful engine… 
It’s normal for the process to grab a lot of system resources and in some cases best done when you don’t need the computer.
If it completely stalls your machine, a likely culprit is when people turn up the light map resolution too high and/or have an insane amount of light sources in their scene.
I do not do anything else when Unreal Builds Light
And no i don’t put a lot of light and the settings is to " preview "
I meant these settings, found in either the asset window or details tab for each object:
Hm, but im using the Redwood pack, i think he is optimized MW Mountain Redwood Trees Forest Biome in Environments - UE Marketplace
Because i can freeze with a less greedy project, i never had a problem like this before, with my ancient I5 quad core too
Oh, so it also freezes if you just try to bake lighting in an empty or almost empty scene?
No, no. It freeze when there is a minimum asset on the scene, when it’s empty i can build the lightning. But in my level a bit big with Redwood i cannot build whitout freeze, but i see a post on the answer hub who said if i put the light to movable it will resolve the problem, clearly i dont know why but i was able to do 2 consecutive build so i tried to do the same in another project, i put the light on movable but this time, freeze at 88% so i return to my previous level (Redwood) and again, freeze at 89%
I found this:
“Lightmass will Crash if it runs out of memory. This is often reported as a bug, but it is simply a limitation of your system setup”
Source:
Although I’m not entirely convinced that this is what is happening to you.
Maybe you can try to further optimize the scene, so turning down light map resolution of your objects and placing lightmass importance volumes
Omg it will take so much time, i have a lot of asset in the scene… But placing light mass, are you sure it will ne helpful ? (I dont know what’s the utility of light mass)
I will try to do a new scene again only with the Redwood’s asset and apply what you said. Do you have something to talk easyer ? Like discord ? It’s faster than come to this page