Can someone please explain to me how building all and lighting works in UDK?

I get the message : no importance value found, lighting build may take a long time

I looked this up but I am not sure how it works. Also- for light mapping to work properly static meshes must have two sets of UVs correct? just the same as if you did lightmapping in Maya?

1. when you build all, that rebuilds bsp, paths and lights. build light builds lighting only. the error you are getting is because you need a lightmass importance volume. to add one, just right click on the volumes and add one.

scroll down to lightmass importance volume
http://www.hourences.com/tutorials-ue3-lightmass/

2. yes. if you are repeating meshes, they will need proper uvs for light mapping. udk (maybe other engines as well) will only accept seams that are vertical also. heres some links

http://udn.epicgames.com/Three/LightMapUnwrapping.html
http://www.hourences.com/tutorials-ue3-lightmapping/

Hi Blacknine. You get that message because you need to add a lightmass importance volume around the playable space in your level. Everything contained within that volume will get the amount of bounce lighting you have set within the lightmass properties and will have better quality. (Usually 3+ bounces) Anything outside of that volume will be only one bounce. This is to save time on bakes.

Build Lighting will build only lighting within your level. Build all will build everything, including geometry (BSP), paths ect.

In order to bake light maps within UDK yes you do need to have a second UV set. Hope that helps!

Edit: Bah Oniram beat me to it :P

Originally Posted by Snight

Edit: Bah Oniram beat me to it :P

:P