Since I upgraded to 4.18 it seems like Lightmass spends most of it’s time processing the Skylight Radiosity. Is this common on other people’s systems as well? I just upgraded my processor to a fx-8320e for more threads and I have 16gb of ram. The processor cores are all at 100% and the memory usage is around 50% with little to no spikes on harddrive performance while I’m building my lightmaps.
Hi!
I guess it depends on your settings (number of bounces, scale, quality)… the additional bounces are not “free” as it used to be before…
But yeah the same here: lightmass uses 75% of all cpu, I have more ram but unreal never needed them all…
I’ve tried only 1 light bounce and 0 skylight bounces but skylight radiosity still takes the longest to process for my system. It takes about 1 hour and 30 mins for lightmass to complete and 1 hour and 15mins of that time is just processing skylight radiosity. I’m just trying to make sure something is wrong in my settings or if that is normal since 4.18.
Well again it also depends on your scene… number of objects + lightmap resolution + those other settings… but it shouldn’t be that long I guess!! Should be the same speed as it was with earlier releases!
Happy Christmas! 
I noticed the same exact thing when I upgraded to 4.18. I let a light build run overnight (archviz VR) and after 12 hours I was at 6% complete using 30 cores swarmed together. After that, the mappings finished processing in under 5 hours. I’ve been tweaking settings to try to cut down render time but haven’t found the key yet. I only have 5 skylight bounces and all lights except one are static. It does seem like the same setting used to take much less time to compute though.
anyone found an answer for this as i’m having the same problem 12 hours of Skylight Radiosity and still 0%.
Using only 5 skylight bounces in world settings and Average lightmass is 256 for the archiviz scene.
Anyone found any solution for this? My scene is not that complicated. It just has a fair bit of fauna and I have been told that it should take about 5 minutes to build my lighting; but after an hour, I’m still under 6%. I have an i5-6600 8 GB ram GTX 1060.
Hi!
…imo it would be really helpful if any/all of you would post your settings (lightmass) too and not just the fact that it’s slow!!
Hello, I had the same problem and just found the work around changing 2 things (for every mesh, lol), I’m using 4.24.3 version of the engine in case you don’t have the same tools or menus.
A lot of my meshes had too much triangles, for example I had a tiny TV Remote Control over 500.000 triangles. For this issue you can open the Statistics Viewer (from main toolbar Window->Statistics), select Primitive Stats from the first dropdown menu and order your meshes by Tris, if you see something like my Tv RC mesh problem, open the Static Mesh Editor for every mesh and in details panel under LOD 0->Reduction Settings low the Percent Triangles for the mesh. I have a mesh statistics inside the editor viewer to see the quantity of triangles and you actually see the effect of lower percentage have in your mesh for desired results.
The other thing to change is the lighmap resolution of your meshes. You can see the lightmaps for all your objects in scene by clicking the lightning dropdown menu inside the main editor (for me LIT->Optimization Viewmodes->Lightmap Density), where green is low resolution and red is high resolution, try green and see if this was causing the error, you have to read more about this to know whats the best configuration for your project. In details panel of every mesh under Lightning check the Overridden Light Map Resolution and play with it to find the result you want. Or you can change the lightmap for all of your objects clicking the small arrow to the side of Build button->Lightning Info->Lightmap Density Rendering Options, play with the Ideal and/or Maximum to get the result you are looking for.
You can make the number 1 tip on your 3D tool of your preference too, I guess its more recommended.
Hope it can help other people with the same problem, have a blessed day.
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