Lightmass with bad shadow (again) in 4.5

I build some modular level and I fixed bad lighmass seams using settings taken from this topic:

Static Lighting Level Scale: 0.1

Indirect Lighting Smoothness: 0.6

Indirect Lighting Quality: 2.0

Unfortunately after updating engine to 4.5 seams came back to life:

Have you gone back into your settings and made sure they match the settings you posted? Also have you rebuilt your lighting? It also seems that the resolution on your modular pieces are a bit low. Try raising these values and after following these steps, you still see seams, let us know and we will assist you further.

I would also check that your mesh (If you are using a mesh) has the same settings as it did before you upgraded. A few of the import settings changed on meshes, such as auto generate lightmap UVs and auto generate collision.
If you are going to have a lightmap as lo res as the one in your screen shot you should make sure the seam of your U.V. is snapped to the texel edge in your modeling package.
Example: For a 128*128 lightmap, set the grid of your UV layout window to 128 and then snap all your UV points. If the edge is a straight line you will never get a shadow bleed, even when the light map mips down.

I opened my old level in 4.5 and I checked settings once again. I tested different UVs. The ones which gave me good results in 4.4 and the ones generated by engine 4.5. Either way the seams are still there.

Results between two identical walls with LM resolution of 128px (see full resolution)

Problem seems to appear only with indirect lighting. Results with point light near seam (lighting baked once again):

Is that second screen shot using a “baked” static light? The shadows from those pipes look as though the point light is stationary or moveable.

The indirect lighting is always baked by lightmass which in your case is to a 128128 lightmap. The stationary shadows will also need to be baked to show up but will look much higher res than 128128. Stationary and Moveable lights wont have the seam problems but the indirect part of the lighting needs a good UV layout.

In the first shot though, the seam looks more like the entire wall has a different value.

You can increase the indirect lighting intensity to like 5 to see this helps shed brighter lights on your other objects as well. I suggest also not sticking to the specific values that were mentioned in the AnswerHub post you linked, but finding your own. Not all scenes are the same so not all the values will need to be the same in that sense.

Try increasing your modular pieces resolution to something like 512x512. Increase your indirect light intensity, and also play around with the global lighting settings in your world settings to help eliminate the seams. Keep in mind there is no way to completely eliminate seams. Just a way to “overexpose” them or mask them with lighting value changes. I hope this helps resolve your issues.

Here is some documentation on lightmaps and how they function and how to optimize them as well:

Keep in mind this is referencing UDK, but the general set-up and information is the same


First and second shot was made in the scene lid by stationary lights. Spot is also stationary.

Yes that makes sense. You wont see the seams from the stationary light. Its the indirect or ambient that is showing that seam. You best bet is to up the resolution of your lightmap a bit and try to put the seams right on the edge of the UV layout, that will effectively snap them to the texel edge.

There seems to be a few people trying out procedural levels that have the same problem as you.