DCC production guide
Lightmap UV Overlap Fix Checklist
Direct answer: A lightmap UV is ready when the engine can bake lighting from a dedicated second UV set without unintended overlap, insufficient padding, or islands outside 0–1 space. Texture UVs may mirror or overlap for efficiency; lightmap UVs usually cannot because every baked lighting sample needs a unique surface location.
Lightmap UVSecond UV SetUV OverlapMip BleedingTexture Bleeding光照贴图 UVライトマップUV
UV1 versus UV2 decision
Keep the first UV set optimized for materials and tiling. Put baked lighting into a second UV set when the engine supports it. If the mesh is dynamic, fully movable, or uses only runtime lighting, a lightmap UV may not be required; if it receives baked GI or static shadows, it usually is.
Padding by resolution
Padding is project-defined, but the rule is practical: lower lightmap resolution needs more pixel padding. For example, a 64 px lightmap may need visibly wider island gutters than a 256 px lightmap. Padding must survive mip levels, not only the top texture.
Overlap triage
Find whether overlap is intentional texture mirroring or accidental lightmap overlap. For lightmaps, split mirrored shells, move stacked islands apart, and repack. Keep shells inside 0–1 unless the target pipeline explicitly supports virtualized or tiled lightmaps.
Bleeding fixes
Mip bleeding and texture bleeding appear as dark seams, bright leaks, or color crawling near UV borders. Increase island padding, straighten important borders, align hard edges with UV splits where appropriate, and rebake after changing the layout.
Engine verification
In Unreal, Unity, or custom bakers, inspect the imported UV channel index, overlap warnings, lightmap density view, and baked preview. Do not approve from the DCC viewport alone; the engine may choose a different UV channel or regenerate UVs.
Worked review example
For a modular wall kit, inspect every repeated piece at the same bake resolution. A trim texture may reuse UV space on the material channel, but the lightmap channel should give each wall face unique space. If two wall modules share a seam, their island padding should be enough that indirect lighting does not bleed from a dark backside into a bright front face. After repacking, rebuild lighting and compare density view, overlap warnings, and the actual seam in the assembled corridor.
Multilingual production terms
Use this lightmap uv overlap fix checklist terminology table when writing review comments, export notes, or handoff instructions across Chinese, English, and Japanese teams.
| 中文 | English | 日本語 | Workflow usage note |
|---|---|---|---|
| 光照贴图 UV | Lightmap UV | ライトマップUV | Use these terms when separating material UVs from lightmap UVs and reporting padding or bleeding fixes. |
| Mip 出血 | Mip Bleeding | ミップブリード | Use these terms when separating material UVs from lightmap UVs and reporting padding or bleeding fixes. |
| 第二套 UV | Second UV Set | 第2 UVセット | Use these terms when separating material UVs from lightmap UVs and reporting padding or bleeding fixes. |
| 贴图边缘出血 | Texture Bleeding | テクスチャブリード | Use these terms when separating material UVs from lightmap UVs and reporting padding or bleeding fixes. |
| UV 重叠 | UV Overlap | UV重なり | Use these terms when separating material UVs from lightmap UVs and reporting padding or bleeding fixes. |
Term notes for multilingual briefs
Use the English term Lightmap UV with matching Chinese/Japanese notes where relevant: Texture Bleeding / 光照贴图 UV / ライトマップUV. Keep the technical term beside the local-language note so reviewers can map it back to DCC and engine settings.
Related pages and next step
Open SEELE AI workspaceFAQ
Can texture UVs overlap while lightmap UVs do not?
Yes. Material UVs can overlap for mirrored detail, but baked lightmap UVs typically need unique, non-overlapping islands.
How much padding is enough?
Use the project lightmap resolution and mip policy. As a practical example, smaller resolutions require larger relative gutters.
Why do seams appear after a clean bake?
Common causes are too little padding, wrong UV channel assignment, hard-edge mismatch, or islands too close for the target mip level.
Should I let the engine auto-generate UVs?
It can work for simple assets, but hero props and modular kits often need manual review because auto unwraps may waste space or split visible areas poorly.