White face on `DamagedHelmet.glb`

[snoyer]

When viewing DamagedHelmet.glb in F3D there strange white part on the underside that isn't white in other viewers; see below image comparing (left to right) Meshlab, gltf-viewer.donmccurdy.com, and F3D:

It looks like it could be an unfortunate reflection in the screenshot but it stays white when moving the camera around:

whiteface.mp4

Could still be lighting-related as it interacts with bug #1506 in the wasm version: the part is correctly displayed in the "first render is incorrectly lit" state and becomes white when the "correct" lighting kicks in:

whiteface-web.mp4

@mwestphal reports "it is present with the vanilla GLTFImporter of VTK"

[Meakk]

No exactly sure why yet, but there's an issue in the tangent computation.
Could be the tangent length close to zero, or the tangent being colinear with the normal.