TOTALLY WRONG SHADOWS after light build

Hi guys,

I’m working on my first ArchiViz project, I’m modeling buildings and stuff in Blender then importing in our beloved UE4…
Here is my workflow, please correct me if I’m doing wrong… well I:

a - model the building in Blender
b - try to make an accurate unwrap for 2 UV channels (first for the textures, second for lightmaps)
c - export the model in .FBX format
d - import in UE4
e - make the material and apply it to the imported model
f - build light

SO, this has been perfectly working for many meshes that I’ve already imported, but now (few days from the deadline, of course) on one particular building
I’m getting SUPER WRONG shadows after the point “f”, as you can see below. D:

S_0006_Screenshot (1).jpg

The scene is lightened by a Directional Light and a Sky Light.
The model is actually very clean (all normals pointing out, no mess at all).
The building is formed by 3 meshes, one for the red building, one is the roof and one for the front elements.
Lightmap resolution is set to 256 on all the 3 objects, but in the same scene I have meshes which has way better shadows with lower values.
I have tried ALL the different levels of light build, from Preview to Production but I get the same result.
I would be VERY grateful if someone could help me out with this! :confused:

I hope I have been clear enough, I’ve tried to upload more screenshots but the database of this forum kept crashing continuously.

Thank you!

Your lightmap resolution is too low, 256 means 256x256 pixels which is very small for something that large. You can try 1024 or 2048 and see if that improves enough, if not then you’ll have to split the meshes further and redo the lightmap UV’s so that you can have more lightmaps.

Hi darthviper107,

thank you for your answer.

I tried pumping up the Light map value to 1024 but the result really doesn’t change a bit. As you can see here, I did already modeled and imported another building without problems
(the one you see here has a Light map res value of 128!).


I tried slicing the issued building in 3 pieces and reimporting, trying different ways to unwrap the meshes for the UV maps… This is getting a little frustrating, really -___-

Did you rebuild your lighting? I can tell you 100% the issue is due to a low resolution lightmap, if it’s not getting better with a higher resolution then you’re doing something wrong outside of the normal workflow

A huge building like that is just 3 meshes? That’s not gonna work very well unfortunately. I have smaller buildings that are 500+ meshes. You need to model in smaller pieces if you want to achieve good results with lightmass. In your case, if you don’t want to re-model everything you might want to try to use dynamic lighting instead. For exterior shots is could be fine with some AO.

Hi heartlessphill,

thank you for your answer. Actually as I said this is my first project on UE4 so every tip is really useful for me. The yellow building in the second image I posted is made of different, smaller blocks and in fact shadows works perfectly on it even with a Light map resolution of 128.

I’ll try your way, hoping in best results, thank you very much for now :slight_smile:

If the project isn’t too confidential and you are willing to send me the files I could have a quick look at it for you.