Hi, I’ve recently started learning 3d modelling in blender and I’m trying to get some of my models working in unreal however I’m having problems with the shadows bleeding through on the model. I’m not sure if it is a problem with my light maps or with the models or something else. I’ve had a look at the guide for lighting problems as well as a bunch of other stuff but I cant quite work it out. Do you have any ideas on how to fix it or where I could look to find answers?
You shouldn’t split up the UV’s on every polygon, you can improve the results if you keep each side together in the UV’s and flatten them that way. Besides that, you’ll need to make sure that your lightmap resolution is high enough. Also, if you don’t need to see the bottom then you can delete the bottom polygons.
With lightmass, I wouldn’t suggest delete bottom/back polygons. Meshes that aren’t closed off can create more issues with lightmass. You can resize the lightmass UVs for the back and bottom to be tiny, so the resolution isn’t being wasted.
My guess is the biggest issue is resolution.
Second is that you are splitting flat areas that should remain connected as one piece.
It looks like you could stand to increase the padding between islands a bit. Are you getting any overlapping errors?
Thanks, I think I’ve improved it a bit by upping the res, spacing it out (although I wasn’t getting any overlap errors) and connecting some of the pieces. When it comes to creating the islands, I’m not 100% sure where I should be making the splits. I’ve tried a few different ways but the indents in the model still don’t look great. Should I be splitting them like the red or blue in the attached picture or some other way?
Your first unwrap was the most proper one and generally well-done, apart from few pieces that were slightly skewed and off scale. You have long and short sides, but in the unwrap they are nearly the same length. Lightmass hates it.
But your initial lightleaks are caused by something else. Your mesh seems to be done in a such way, that the area marked by red line has either no thickness or insufficient thickness. No amount of lightmap tweaking will help you with that, unless you add some mesh thickness there.
Thanks! That helped a lot, its not quite perfect but fixing the spacing on the model definitely seems to have fixed most of the problem. I guess I’ll just keep having a play around with the lightmaps now until I start to get it into a better place
Deleting the bottom faces will not cause any problems for this particular piece. The meshes where you’d likely want to keep the back side would be for things like walls.
Here’s a good example on how to do the lightmaps:
Reducing the number of seams will help with lightmap issues
Thanks for the help everyone, in the end the best results I could get was by cleaning up the model quite a bit and then by using Blender’s automatic lightmap pack function. When I was trying to keep the light map in islands I kept getting bleeding on the tops of the indents on the sides.