Recalculate Normals and Tangents Guide

Normals versus tangents

Normals describe surface direction for lighting. Tangents describe the local direction used to interpret tangent-space normal maps. A mesh can have correct face normals but wrong tangents, causing normal-map seams. A mesh can also have correct tangents but flipped faces, causing missing surfaces or black bakes.

When to recalculate normals

Use it after topology repair, mirrored import mistakes, face orientation fixes, or scan cleanup. For hard-surface assets, decide whether to keep custom weighted normals or regenerate by face angle. Recalculation should match the intended shading style: crisp bevels, smooth organic forms, or flat mechanical panels.

When to recalculate tangents

Use it after UV edits, normal-map rebakes, tangent-basis changes, or engine import changes. If the project expects MikkTSpace, bake and import with compatible settings. Recalculating tangents in the wrong tool can create seams that were not present in the baker.

Failure diagnosis

Black faces often indicate flipped normals or backface culling. Wavy highlights can indicate bad smoothing or weighted normals. Normal-map seams often indicate tangent basis mismatch, UV split mismatch, or compressed texture artifacts rather than a simple green-channel issue.

Worked example

A hard-surface crate imports with rounded panels that should be flat. First check face orientation. Then restore weighted normals or hard edges on bevel boundaries instead of smoothing the entire mesh. If a normal map is used, rebake or regenerate tangents with the same basis used by the engine before approving the fix.

Term notes

Related multilingual terms on this page are technical anchors, not one-to-one translations: Recalculate Normals / Recalculate Tangents / Face Orientation / MikkTSpace / Flipped Normal / 法线重计算 / 切线重计算. Keep local-language notes beside the English production term when writing DCC tasks.

Related pages and next step