UV Lightmap Pack takes each of a mesh’s faces, or selected faces, and packs them into the UV bounds. Lightmaps are used primarily in gaming contexts, where lighting information is baked onto texture maps, when it is essential to utilize as much UV space as possible.
Do I need Light Map?
Lightmaps are only required when a Static Mesh will be lit using any form of baked (or precomputed) lighting. If your game or project is only using dynamic lighting, there is no need to set up lightmaps for each Static Mesh. For the majority of Static Meshes that you import into UE4, you’ll be able to use an auto-generated lightmap UV because a good result can be achieved with minimal effort. However, for those times when it’s not possible to adequately use an auto-generated UV, you’ll want to create a custom lightmap unwrap in your modeling software or UV editing tool.
- Share Tex Space is useful if mapping more than one mesh. It attempts to fit all of the objects’ faces in the UV bounds without overlapping.
- New UV Map if mapping multiple meshes, this option creates a new UV map for each mesh.
- New Image assigns new images for every mesh, but only one if Shared Tex Space is enabled.
- Image Size Set the size of the new image.
- Pack Quality pre-packing before the more complex Box packing.
- Margin controls how closely the UV islands are packed together. A higher number will add more space in between islands.
Blender 3D Manual – Mapping Types: https://docs.blender.org/manual/en/latest/modeling/meshes/editing/uv/unwrapping/mapping_types.html
Unreal Engine 4 Doc – Unwrapping UVs for Lightmaps: https://docs.unrealengine.com/en-US/Engine/Content/Types/StaticMeshes/LightmapUnwrapping/index.html
Lastly Edited: 25. Nov. 2019