Bump
The realism of the stitching’s appearance is due, in part, to the bump texture.
The texture of this type of material is assembled from two different image maps: a Pleat Map and a Seam Map.
The Seam map gives the pattern for the individual stitches. Without this map, the material would be entirely transparent. The color of the diffuse filter will fill in the lighter areas of this image. The zones with an alpha background will remain transparent, showing the material assigned to the surface below the seam surface.
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Example of a seam map. The checkered zones represent an alpha background.
If the material is gathered or pleated under the stitching, use the Pleat map settings to impose the texture.