The problem was two-sided material (replaced by one-sided ), not supported point light length ( replaced by spot), and sparks made from the one of LED emitter in my coffee machine model ( added node LightmassReplace to avoid bake cause all what is an emitter is used to add the light to the scene by the GPU Light mass).
Bake time 10 min. And I was very surprised when I saw that bake with active Swarm (I have prepared for net bake on CPUs) is made on all machines that have GPU on board in the network.

It also works if you set emissive boost to that staticmesh to be 0.0

Ray clamping 2:

General question, I'm still having these spots when it comes to direct lighting (attached images), I'm using stationary lights, production settings and Num Indirect Lighting Bounces=100, should I look into other values if this is done in CPU, or where should I be looking to fix this?

for those of you who have problems with grainy/splotchy lightmaps.
you can workaround this by upping the indirect lighting intensities of your lights from 1 to 3-6. depends on the lighting situation and the light intensity of the light.
if your scene then gets too bright, you can cramp up the eye adaption/exposure min/max brightness settings. to something like 0.4-0.5 also highly depends on your environment and lighting situation. but this way i can also use the GPU baker in critical conditions.
not ideal, since f*cking with the post process settings will also affect your exterior views and quickly you changed the complete nice lighting settings you had..but well it is a workaround

this is my setting for this scene plus {large lightmap size 1024...2048...}
and nothing special !




Static Lighting Level Scale : 0.15
Num Indirect Lighting Bounces : 15
Sky Bounces : 5
Indirect Lighting Quality : 10
Indirect Lighting Smoothness : 1

"Lightmass parameters and quality settings specified in the editor are ignored except for Num Indirect Lighting Bounces"

i just made a test,
you can change the baselight.ini on the fly, no need to restart.
which is awesome

've uploaded a new 4.20.2 version which allows you to set GPULightmass quality settings directly in BaseLightmass.ini without swapping between different versions. Scroll down to the end of BaseLightmass.ini and find DevOptions.GPULightmass. A better way is to create a DefaultLightmass.ini under your project's Config folder which only contains the DevOptions.GPULightmass section so that you can have per-project settings.
Note: GPULightmass still ignores legacy Lightmass quality level, because while therotically I can make them connected, that may be very confusing.



As a comparison, the parameters for the presets are:

FastPreview:
NumPrimaryGISamples=16
NumSecondaryGISamples=8

MediumQuality:
NumPrimaryGISamples=32
NumSecondaryGISamples=16

UltraHigh:
NumPrimaryGISamples=64
NumSecondaryGISamples=16

Extreme:
NumPrimaryGISamples=128
NumSecondaryGISamples=32

Your rendering time is roughly propotional to the square of these numbers. Power of 2 is recommended. Also do not set the numbers too low or too high as that may cause strage problems (completely black, artifacts, or crash and TDR). Especially when you tune up NumSecondaryGISamples you will want to increase TDR.

Hi! Please tell me how to get rid of noise and stains on the walls when using GPULightmass. Lightmass walls 2048. Unreal 4.20.3
Increase quality settings in DefaultLightmass.ini (try 64/32 or 128/32); or use brighter lights.

Are the emissive materials working on 4.20.2? I've tried to light some areas by using the emissive but it´s not working.
Should be fixed in 4.20.2 unified settings now. It is caused by firefly clamping introduced in 4.20.
Now firefly clamping threshold (10) is exposed through ini.
This technique aims at removing fireflies by making your image biased (darker).
Threortically speaking it should be set to the maximum brightness in your scene.
In practice you can set it to a high initial value, then keep lowering it if any firefly is seen.

I've confirmed multiple times that emissive is working in the newest unified settings version. If it doesn't try checking whether it is too bright that it is clamped by the FireflyClampingThreshold. If that is the case raise FireflyClampingThreshold to something like 10000.0

Yep, landscape's static lighting resolution is a multiplier on 'how many lightmap texels per quad' - even 8 is considered to be very high.
Landscape - 512 is pretty extreme, even 128 is still very high. Don't forget to check the lightmap density via Alt+0, just to make sure you're using the optimal res.

I've used the script installer to get better results (LightmassConfiguration.bat). With Ultra High Quality the noise is less noticiable, with Extreme and Insane quality the noise is gone.

Try doing testings with a basic level and see if some of these settings are ok for you.

https://forums.unrealengine.com/development-discussion/rendering/1460002-luoshuang-s-gpulightmass/page38