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Thread: Lightmap Seams

  1. #1
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    Default Lightmap Seams

    I know this issue has been brought up on here A LOT, but I still can't seem to find a fix for it.

    I've moved from a BSP structured level to modular static meshes recently and can't get rid of the horrible seams between the meshes.



    I have tried different lightmap UVs in channel 2 (3ds max) with stitched and unstitched, vertical and horizontal variants.



    and also upped the lightmap resolution.

    The problem seems to intensify the further away from the mesh that I move.




    I have also tried playing with my light settings. Upping both "WholeSceneDynamicShadowRadius" to 3500 and "NumWholeSceneDynamicShadowCascades" to 2. To no avail.

    Should there be a poly between the static meshes or not? I have tried both!
    Also tried a material made up of just a constant 3 vector for the diffuse incase it was a tiling issue.

    Any help would be MUCH appreciated.

    Thanks.

  2. #2
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    Couple of suggestions: Increase lightmap density on your object. I see it's at 256 now, so I'd put that at the second option. The first thing to do is make sure you are snapped to pixels in your unwrap. In your example, use a 256x256 checker and make sure all edges are on pixel edges in the unwrap. In UDK, re-bake at production level to check it out.
    Let me know if that works for you!

  3. #3
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    Try removing any smoothing you ahve on the meshes and see what happends

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    Try selecting the coplanar surfaces that share the same texture, right click and then Alignment -> Planar wall. This worked for me with floors, although I tried also with walls and it didn't U_U. Hopefully it works for you.

  5. #5
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    Quote Originally Posted by Tearl View Post
    The first thing to do is make sure you are snapped to pixels in your unwrap.
    This was the step that I had missed and it improved the lightmaps A LOT. There is still a slight seam in there but I'm thinking this might be to do with lightmap resolution now. Is it possible to have a completely seam free wall? I'll investigate further and post back any progress.

    Thanks for the help.

  6. #6
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    Is there somewhere that you can alter how lightmap LODs are used? It get's noticeably worse from 10ft or so away!

  7. #7
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    As I said earlier "Try removing any smoothing you havee on the meshes and see what happends"

  8. #8
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    How can this be solved in BSP-built maps? Planar alignment only works for floor and ceiling for me; for walls the texture is moved but specularity doesn't match.

  9. #9
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    Quote Originally Posted by Maffew View Post
    Is there somewhere that you can alter how lightmap LODs are used? It get's noticeably worse from 10ft or so away!
    In BaseEngine.ini look for:


    AllowStreamingLightmaps=True

    and set it to False. This will force the highest level of lightmap mipmaps to be used regardless of distance. Helps a lot in my experience. In theory it hurts performace, but quite honestly i havent seen a decrease in fps at all.

  10. #10
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    Quote Originally Posted by ankangronto View Post
    As I said earlier "Try removing any smoothing you havee on the meshes and see what happends"
    Yeah, thanks for that. It wasn't really a smoothing groups issue.

    Quote Originally Posted by hunharibo
    AllowStreamingLightmaps=True
    I'll give this a go this afternoon. Cheers.

  11. #11
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    Quote Originally Posted by hunharibo View Post
    In BaseEngine.ini look for:
    AllowStreamingLightmaps=True and set it to False.
    This worked a treat. Hasnt dopped my FPS at all from what I can see. Thanks.

    If anyone else is trying to fix a similar problem you really have to make sure you follow every step in the static mesh pipeline.
    1) Make sure you have a second UV channel with unique UVs for lightmaps.
    2) Make sure you have sufficient padding around UV islands (remember that the lightmaps are probably going to be pretty small so this avoids bleeding onto other islands)
    3) UV seams should snap to the grid in the UV window
    - I did this following Tearl's suggestion of making a checkerboard pattern the size of my desired lightmap and snapping the seams to the checkers. Like so:

    4) Smoothing groups on adjacent surfaces should be the same.
    5) 'AllowStreamingLightmaps' should be set to False in BaseEngine.ini (This probably isn't ideal for everyone but helped me a lot.)


 

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