[UE4 and 5] GPU Lightmass / Light bake

Reason : Lightbake is still widely used for VR and Games for optimization. Lumen tends to be expensive to run in games and VR headset sometimes.

*UE 5.7 

Project Setting : GPU Lightmass On

Build Tab -> GPU lightmass

Step by Step : light bake prep

Project Setting : 

To see how light looks like before bake it, utilize Pathtracing is very helpful

To turn on Path Trace, You need to set project setting like this

Lightmap Density

Viewport : Lightmap Density

StaticMesh Window : Turn on Generate lightmap UVs

All meshes has to be static mesh (except animated object)

Destination lightmap index : 2

Lightmap resolution : depends

 : Lightmap resolution is different based on the size of the mesh. Change the number until you see a green color on your view port. Blue is too low res and Red is too high res. 

Lightmap Coordinate Index : 1 

 : Meaning it will use UV Channel 01 as Lightmap. Generally UV channel 00 is original Mesh UVs. and Channel 01 is Lightmap.

PostProcess : 

GI and Reflection : Lumen -> None

Megalight : off

Lighting : 

All lighting has to be Static

Reflection :

Add reflection capture (generally Sphere)

Set basic Material, lighting and run on path trace to see the lighting. *Pathtracing Mode

GPU lightmass : 

Turn off realtime viewport for faster light bake

Build -> Build reflection capture

Result : After lightbake and build reflection capture

Light will be remained even though you delete the light

All light bake data is under BuildData. If you delete, you are no longer able to see lightbake on viewport