Baked Lighting Discontinuity, leaks and seams
Hi! I've been messing around with a very simple test level to try and work out how UE4's baked lighting behaves. I was planning on using some procedurally generated rooms consisting of multiple static meshes - however, constructing a very crude mockup shows a whole bunch of odd looking lighting behaviour. There is light seeping, and in one example an entire bsp displaying the wrong lighting level.
Some of this is previously logged - I know that lightmass doesn't like multiple static meshes, so seam covering can be a good idea - but I am wondering what the best steps to take to avoid this type of problem would be.
The only light active in this scene is a single directional light.
asked Aug 16 '14 at 03:19 PM in Rendering
This is actually a known issue resulting from lighting be baked on different threads. The best solution is to have seams at corners or have other meshes that are used around these seams.
This has been discussed multiple times on the forums and here on AnswerHub.
This is a solution that will help some: https://forums.unrealengine.com/showthread.php?8491-Baked-Lighting-Variation-Between-Static-Meshes
Also adjusting the Static Lighting Level Scale to .75 or .5 will help but this will increase your light build times.
answered Aug 19 '14 at 07:09 PM
Tim Hobson ♦♦ STAFF
I want to add an additional comment here that I don't think is in the above. Bias for lighting has been a long known problem in all work CG related, and is no different here. Yes, having goodish UVs is important. If your UVs are for a gigantic structure, you won't get many pixels devoted to any single part. I generally break things down quite a bit.
Additionally, there is known problems with your UVs being too close, creating bleed. So a face on one side of the object may interfere with another face elsewhere that is tangent to it.
But mostly what I wanted to say is that BIAS is a problem. It causes shadows to move off the surface, and cause gaps between objects. The bias is found on the light that is creating the shadow. The default bias is .5 I believe. I have had to make my bias .1 to close that gap. Now if you go too small, you will get artifacting, or self shadowing. The polygon faces will get sort of diagonal striations of shadows as it tries to cast shadows on itself. The lower the number the worse it will get. You need to find the sweet spot, between making the shadow move away from where the objects meet, to creating self shadow artifacts.
Bias. Don't underestimate it.
answered Oct 24 '14 at 03:57 AM
Follow this question
Once you sign in you will be able to subscribe for any updates here