Lightmap memory usage vs actual size of the map

Hi Everyone.

I am still new to Unreal, and I am trying to understand better about how Unreal manages its lightmap usage memory.
The question is when I take a look at the lightmap generated in the world setting, their texture sizes are pretty large and their resource size memory is understandable. But when I open statistics window and take a look at static mesh lighting info, it looks like it has considerably lower memory usage in both total and its individual size.

I can understand that the maps that I see in the world settings are the atlas packed maps, so they are larger by design. But the total memory used for those textures vs what is indicated in the statistics are way different.

Even after consider the landscape taking its fair share of space, it still leaves huge gap.

Can anyone explain this for me please?


The lightmaps that are currently being used are going to be far less than what was generated for the map

Ok. Fair enogh. But why is that the case? If it is view dependent, it should change according to the camera angle, position but statistics doesnt change.

It’s not going to be exactly camera view dependent since that would be a problem when the camera is moving in terms of the ability to load in lightmaps fast enough, more than the current view is loaded. Also, it does save lightmaps into atlases so some stuff is loaded in even when not used.

What I am saying is that the statistics for lightmap memory usage is Lower than the total lightmap baked for the level. Much lower. As far as I can understand, all the lightmap atlases should be loaded into the memory. So it is confusing to see stastics showing so much lower memory usage.

is there way to check out total lightmap memory used in the game?

It’s not going to load all of the lightmaps that a level has, it physically can’t

Ok, well, I would still love to find out sum of all light maps baked, in terms of memory usage, so I can adjust overall density of the maps globally.

In the newest verison, doesnt Unreal already use Virtual Texturing for Lightmaps? Which means the Memory usage for Lightmaps is constant, regardless of the actual size of the lightmap data