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Light leaks....what is the ACTUAL solution?

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    Light leaks....what is the ACTUAL solution?

    Hi guys, so it seems no matter what I do, there seems to be no way to remove the light leaks in my small arch vis scene.

    I've snapped lightmap UV's to grid, increased the padding to 4, snapped wall vertices to each other, angled walls to meet at 45 degree, let walls intersect - stopped walls from intersecting, increased lightmap resolution, lowered SLLS.

    I've been scouring the forums and researching and implementing what seems to be every proposed solution, some people say to keep it all as one mesh, some people say to split walls and floors up? I honestly have no idea at this point - does anyone know of any other lightmass.ini tweaks I can make to clean the lighting artifacts up?

    The only thing that reduces them is increasing my SLLS back to 1, which compromises the quality ,and it doesn't even fully get rid of them.

    Would love some insight to solving this persistent issue!
    www.artstation.com/kurtmitchell

    #2
    From that static mesh image, is that mesh closed/water tight? It looks like there isn't geometry bridging the hole. One sided geometry can cause lightmass artifacts, even if the "holes" are covered up.

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      #3
      Originally posted by ZacD View Post
      From that static mesh image, is that mesh closed/water tight? It looks like there isn't geometry bridging the hole. One sided geometry can cause lightmass artifacts, even if the "holes" are covered up.
      To be fair the two window openings didn't have bridges, but the rest of the mesh is tight - I've bridged those small bits but I'm pretty sure there's still going to be leaking.

      For some reason my light leaking is only happening when I build production lighting? why does this happen?

      The image in the first post has a SLLS of 0.3, which gives great lighting and vibrance - but serious leaking issues. I've set it back to 1 in these 3 builds - and as you can see production still has some leaking issues, especially under the set of drawers (no idea how that got there).

      I'm currently building the level with 0.5 SLLS, and those two holes filled, all lightmaps snapped and padded, with tight geometry all over - there shouldn't be a single opening in the mesh. I'll upload some screens when it's done.



      www.artstation.com/kurtmitchell

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        #4
        I feel like there must be a faster way to optimise a scene to prevent these artifacts? I spend so much time doing lighting builds!
        www.artstation.com/kurtmitchell

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          #5
          Hi!

          Your lightmap doesn't seam right... or it was snapped to a 64 sized which is VERY low... Your walls (separate) should have at least 512 resolution!!
          I don't see your other settings (lights, skylight)... but your lightmass settings are not ideal and you'll get a very high build time!!
          These would be my settings:
          SLLS: 01.
          NILB: 5 (max 10)
          NSLB: 5 (max 10)
          ILQ: 10
          ILS: 0.6
          ​​​​​​​​​​​​​​
          ​​​​​​​Good luck!

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            #6
            I read from numerous sources that snapping to 64 is fine because it will upscale with the resolution as it's a power of two, my lightmap size for walls/roof are 1024-2048. My current build time at 0.5 SLLS is like an hour and a half? which is quite long but my settings are high, and I'm looking for a high end finish.

            Lowering ILS is giving me LOTS of artifacts, I'm trading contact shadows for less artifacts already by keeping it at 1.2. Honestly I can't crank up my lightmass settings much more without just getting artifacts, I may try a build with higher ILQ but it would be great to get to the root of the issue so I didn't need to keep overkilling the lightmass.
            www.artstation.com/kurtmitchell

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              #7
              Make sure that the corners where the walls/ceiling/floor meet line up exactly. It also helps if you have an exterior mesh (doesn't need to be detailed) that will block outside lighting.

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                #8
                Well the lightmap you showed us have like 1/3 clear area!! ...waste of space! If you know you'll have at least 512 resolution then build your lightmap on that with it's padding!! You'll have a lot more space for lighting information like that!
                You have 70 light bounce which causes the long building time!! ...and the 2048 lightmaps too!
                Yes of course lowering ILS gives more artifacts!! You set the engine for more detailed lighting! To balance the artifacts you'll have to increase the lighting quality!! This is the method to get rid of those artifacts!
                Don't forget that unreal was made for games and not archviz! So those default lightmass settings need to be tweaked!
                You should get a nice quality render on Medium build under 30 mins!!
                ...do you have portals at your openings? ...and a Lightmass Importance Volume covering your apartment?

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                  #9
                  I'm tweaking resolution for walls constantly so it's going to take too much time to keep having to tweak the gridsize, that's why I went for 1/64 - for fast iteration, I'm happy to have slightly longer build times and crank up settings because I can do other things while it's building - I just want a clean end result - same with the padding, people recommend 4px padding to avoid bleeds, so I can't really size up the walls without encroaching on padding you know?

                  I tried 50 indirect lighting bounces which really doesn't affect build at all past the first few, I was just experimenting with Koola's technique - it doesn't make my builds any longer.

                  Setting ILQ to 10 which you suggested is what is impacting my build times, but the artifacts are slowly disappearing, again I'm not really bothered about the build times too much.

                  And yes I have portals and an importance volume!
                  www.artstation.com/kurtmitchell

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                    #10
                    I went craxy on the 1st month with light leaks. Found out thay modeling is key. All your wall should ve wzter tight with no overlaping. And then I added another thin wall on the inside by just selecting the inside polygons and detached as a plane and gave it a shell modifier that was very thin. I did this to all my walls and it fixed my light leaks. Also, stay away ftom importing some stuff from the web, they are sometimes modeled badly and ue4 hates them. I try to modrl evetything myself.

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                      #11
                      Here's some test renders with a totally watertight mesh, it's strange how different leaks happen at different SLLS modifiers, clearly the "sweetspot" for my mesh is 0.75 - but I really wish I could crank it up more. I kind of wish lightmass was improved to fix this sort of thing, why do you get leaks in UE4 and not in offline renderers like Redshift? What's causing it on a technical scale? Would be great if @DanielW could shed some light on this.
                      Attached Files
                      Last edited by Kogoshi; 12-06-2017, 06:15 AM.
                      www.artstation.com/kurtmitchell

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                        #12
                        You shouldn't have those leaks!! :S Rest of your scene is really nice!
                        Have you tried to bake without the emissive and the spot lights? Just the skylight (if you have) and the directional light?
                        + also with a simple, non reflective light gray material on everything?

                        Comment


                          #13
                          Originally posted by Makigirl View Post
                          You shouldn't have those leaks!! :S Rest of your scene is really nice!
                          Have you tried to bake without the emissive and the spot lights? Just the skylight (if you have) and the directional light?
                          + also with a simple, non reflective light gray material on everything?
                          After reading around some more, I'm starting to think it might be my spot lights causing the leaks - I'm going to continue with the project at .75 SLLS as I've spent too long on this now, but I'll definitely consider that for the future.

                          Although having extra lights shouldn't really cause this issue.
                          www.artstation.com/kurtmitchell

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                            #14
                            Ok so it turns out my two static point lights were causing some light leaks, but the shadows look awful when I set them to dynamic. I need these lights - what do?
                            www.artstation.com/kurtmitchell

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                              #15
                              Are the point lights intersecting with geometry?

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