Lightmap query

Hi, Im relatively new to unreal and im coming from an archviz background.
Im just wondering, what exactly does unreal do when baking lighting. is it generating diffuse textures with baked lighting?, does it generate a simple shadow map thats projected over the texture base?
Also during swarm baking what is happening in the ‘processing mappings’ phase? im having trouble where my scene is getting stuck at 99.7% for hours and hours. There are one or two 2048 maps in my scene that could be the root cause but im not sure?
Ive been through the lightmap densities and everything is green as far as i can see.

Any ideas?


Hi, view the stadistic time build process, firts, select all statich meshes, and changue lightmaps meshes in “2” (little), and build. see the stadistic, and upgrade lightmaps and see info buildtime (screen)

It’s baking an HDR image of the lightmap, just by itself–so you end up with one image that has the shadows, and then an RGB image that represents where the light is coming from so that specular lighting will work correctly. UE4 is a deferred renderer, which means it composites the image together from passes, so the lighting gets added during that part of rendering.
Lightmap resolution depends on how complex the object is that’s receiving it and how complex the shadows are that it receives. For example, a floor is very simple, and you could have a very low resolution lightmap for that, but if you need a lot of detail in the lightmap because of what’s casting shadows then you have to increase it. 2048 is a very high resolution for the lightmaps, I would recommend trying to lower that or consider if the object might need to be split up to use multiple lightmaps.

Ok thats very interesting thanks. As for the 2048 resolution, the actual level is of a 40k sqft supermarket with all of the fixtures and signage, the 2048 map is on the floor so considering all the lights and fixtures are casting shadows i think id need a higher resolution but i think i probably could break this down into more manageable chunks. same for the roof really. Do you have any idea why the processing mappings stage takes so long?

Yeah, it’s probably better to split that type of thing up, that way it can even unload the parts that aren’t visible.
Not sure what processing mappings means, it’s hard to know what could be causing that.

Its very strange. Usually it keeps the pc that submitted the job and a single swarm node processing and the rest of them disconnect. Im wondering if its either a network bottleneck or something.