I really hope to get some help because I'm at my wits end trying to get Cycles bake to work with me here. For context, our team is using a mobile game engine to run a 3D explore-able world. The world is mostly geometric/architectural so nothing crazy. Unfortunately when baking diffuse for lightmaps (in secondary UV using SimpleBake with Denoising) there's always, ALWAYS distracting seams between close geometry (including instances of light bleed):lightbleedholes near close geometryobvious seam(and many more similar examples)

As much as I wish this were a simple UV bleed problem, there's ample padding between islands and the baking margin is pretty generous (but not enough to bleed into neighboring islands of course). regardles of how I generate the UVs (done this 10s of times at this point) the seams are always in places where geometry get close or intersect. I use Smart UV project as the unwrapping method then use PackMasterPro V2 to pack them as efficiently as possible.

Some troubleshooting:

  • Increasing lightmap size (to 4k): Nope.
  • spreading across 2 lightmaps, doubling lightmap resolution (2 4k maps): Nope.
  • Optimizing UVs to use as much texture space as possible: Nope
  • Removing all unseen geometry and making sure all surfaces minimize intersection: Nope.
  • Supersampling the bake resolution then downsizing resulting maps: Nope.
  • Triangulate meshes so tris are consistent: Nope.
  • Disabled all displacement modifiers and materials: Nope.

My last reprise at this point is to re-do the mesh so it's watertight and there's no possible place pieces of free geometry can get close or intersect anywhere. This feels like an excessive solution for such a seemingly simple problem. We haven't had a problem close to this when using Unity to bake lighting... am I missing something?

  • $\begingroup$ Hello and welcome, please add some screenshots to show us more about the issue, remember, the more, the better to help you $\endgroup$
    – Emir
    Apr 1, 2021 at 1:32
  • $\begingroup$ Sorry about that, added pictures to help $\endgroup$
    – CaseyCo
    Apr 1, 2021 at 1:42
  • $\begingroup$ I am sorry but can you please tell me the basic outline of your problem, so that we can help? $\endgroup$ Apr 1, 2021 at 3:18
  • $\begingroup$ @Aster17 I'm using Cycles bake to bake the lightmaps of an environment, there's 2 4k maps that make up the baked lighting of the scene. Unfortunately there are ugly, distracting black seams and lightbleed in many places, primarily where two pieces of geometry meet/intersect. The troubleshooting steps I took help somewhat but do not solve the issue $\endgroup$
    – CaseyCo
    Apr 1, 2021 at 4:48
  • $\begingroup$ hello, maybe share a file with 2 of these objects so that we can check? pasteall.org/blend $\endgroup$
    – moonboots
    Apr 1, 2021 at 5:22

1 Answer 1


In the Bake margin, change the type from Adjacent faces to Extend.

  • 1
    $\begingroup$ Hi, thanks for the post. This site is not a regular forum, answers should be substantial, stand on their own, and thoroughly explain the solution and required steps. One liners and short tips rarely make for a good answer. If you can edit your post and provide some more details about the procedure and how it works, perhaps add a few images illustrating some steps and final result. See How to write a good answer?, otherwise it may be converted to a comment. $\endgroup$ Sep 24, 2022 at 21:14
  • $\begingroup$ This explains what to do, but not why it works. $\endgroup$
    – TheLabCat
    Sep 25, 2022 at 3:07

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