When I try to build lighting in UE4 the program complains that the level does not have an Lightmass Importance Volume. But then if I try to add one and then build again the program the Swarm could not kick off. What could be the problem? Do i need to configure the Lightmass Importance Volume or do I need to configure the Build settings?
Normally you dont have to change anything in the lightmass volume or build settings to build your light, but you could try to build the light in preview quality. What exactly happens when you try to build the light with a lightmass importance volume? 
One thing you need to do is make sure the Lightmass Importance Volume encompasses your level completely. Depending on the size of your level, the volume might be too small.
I’m facing the same swarm can’t kick off error message.
I’ve tried both with and without a lightmass imporance volume but nothing works.
Has anyone found a solution to this problem?
Here’s the log I get following the can’t kick off swarm message;
MapCheck: New page: Map Check
Cmd: MAP REBUILD ALLVISIBLE
LogEditorServer: Rebuildmap Clear paths rebuilt
LogInstancedFoliage: Map Rebuilt - Update all BSP painted foliage!
LightingResults: New page: Lighting Build - Jun 8, 2014, 11:24:31 PM
LogDialogs:Warning: Supressed: The following levels will not have the lighting rebuilt because of your selected lighting build options: /Game/Maps/Level_3_Junliang_A
LogStaticLightingSystem: Running Lightmass w/ ImmediateImport mode ENABLED
LogStaticLightingSystem: Running Lightmass w/ ImmediateProcess mode ENABLED
LogStaticLightingSystem: Running Lightmass w/ Sorting mode ENABLED
LogStaticLightingSystem: Running Lightmass w/ Mapping paddings ENABLED
LogStaticLightingSystem: Running Lightmass w/ Mapping debug paddings DISABLED
LogEditorBuildUtils: Build time 0:00:02
Hi Bigzer,
Can you post your issue with Swarm on the AnswerHub? We have noticed some issues related to Swarm with 4.2 and are in the process or tracking and handling those issues. When you post, if you have not already done so, can you post your system specs along with the issue?
Thank you!