seam-material

A mesh's polygons drawn on it: a flat fill with soft edges. The look of a modelling program's front and side views, where you read a shape by its topology rather than its lighting. The rig tool's orthographic views use it to line joints up with the mesh.

The edges are drawn in the fragment shader, not as GL lines: each corner of a triangle carries a barycentric coordinate, the smallest of the three is the distance to the nearest edge, and fwidth keeps the line the same width in pixels at any zoom, smoothed instead of stair-stepped. Where triangles shrink to a few pixels across the edges fade, so a distant mesh reads as its fill. The diagonals that split a quad into triangles are not drawn (quadDiagonals finds the quads again; { quads: false } draws every edge). That needs triangles that share no corners, so withBarycentrics(mesh) unshares them (the mesh's skin weights come along, so it still bends) and adds the attribute.

import { seamMaterial, withBarycentrics, seamOverlay } from 'tosijs-3d'

withBarycentrics(mesh)
mesh.material = seamMaterial(scene)
// or, keeping the mesh as it is: a twin drawn in its place
const seams = seamOverlay(mesh)
seams.dispose()

A material without the attribute draws as a plain flat one.