Design Nomenclature / Digital Model Making
Edge Seam
Also called hard edge, sharp edge, split normal, shading seam
This entry has not been translated yet and is shown in English.
A seam in the model itself: a line where the surface is split so normals do not average across it, giving a hard shading break, or where two panels genuinely meet. It exists in the geometry and shows in the render — unlike a UV seam, which exists only in texture space.
In practice
Hard edge, sharp edge, split normal, shading seam: four names for one thing, and every application picks a different one. It costs duplicated vertices exactly as a UV seam does, which is the practical argument for putting the two in the same place.
Not to be confused with
- UV SeamA cut in the UV mapping where the surface is torn open to lie flat. Every seam is a duplication: the vertices along it exist twice in the layout, tangents and normals split there, and no filter can blend across the gap. Put them where neither the eye nor the silhouette goes.
- CreaseA per-edge or per-vertex weight telling a subdivision scheme to pull its limit surface back toward the control mesh, sharpening the result without adding geometry. Weights run 0 to 1, or count integer steps of infinite sharpness. Cheap and freely editable — and carried by almost no exporter.