UE4 Always Freezes When Building Lighting?

Hi everyone, first time posting here. (Eng is not my 1st lang).

i am currently learning UE4 on a weak Laptop:.
CPU: intel i7 Quad Core @ 2.2 GHz
GPU: Nvidia GT 740m
RAM: 6GB
i know that my laptop doesn’t meet the Minimum System Requirements (like i said i’m only learning the software)
the problem is (in a simple Arch-Visualization project that i’m working on) whenever i build lighting on a high res light map (2048x2048 for the walls only) my laptop freezes although lighting quality is set to Preview, and i don’t encounter that problem when building lighting on the default light map res.

i’m thinking that upgrading my RAM (to about 12-16 GB) will solve the problem, BUT if it’s the GPU’s problem, then i’ll just have to wait till i buy a high-end desktop PC.

is it my RAM or GPU?

Hi Am_K_R,

When building lighting it’s a CPU process and not a GPU one. It’s a very intensive CPU process that will take longer for higher lightmap resolutions to calculate.

It may appear that the light build is freezing, it’s just calculating the scene that needs to be built via Swarm Agent.

If you look in your lower right hand corner in the taskbar you’ll find a process for Swarm Agent (Yellow/orange icon with an SA on it). If you double-click and open this. You can check the status of the Light Build process with more detail here.

Higher lightmap resolutions will take longer to build regardless of the quality setting. Using a higher quality will inevitably take longer than the preview build as well.

If you haven’t already put a lightmass importance volume in your scene around your playable area I would suggest doing this. It will only calculate multiple bounces of light calculations within this volume and anything outside will only get a single bounce and lower quality. This can help improve the speed of light builds.

I hope this helps.

Tim

thank you for replying.
yes this is helpful, but one more thing … does installing more RAM help speed up the process, or it just depends on how big my scene is?

RAM can help if you’ve got a larger scene that needs to be calculated, but a powerful CPU is definitely better. A super high-end CPU is not going to make the light build go exponentially faster, although you would probably see a little bit of increase.

The biggest slow down with RAM is that when RAM has run out of space Swarm Agent will use your Virtual Memory space that is allocated and write to the HDD. This is much slower than writing to RAM.

Some things to remember that can bump up the amount of RAM needed to calculate a scene:

  • Lightmap Resolutions. Keep these as low as possible
  • Include a Lightmass Importance Volume around your playable area.
  • Number of objects/lights in the scene increase RAM usage for Swarm Agent and calculations needed to build the scene.

got it, thank you very much.