doubleSided not respected

[emackey]

It appears the viewer is rendering all glTF materials with back-face culling enabled. A flag was added in the past few months to address this:

materials[n].doubleSided (schema)

You can test this with the same model used for testing in #10.

Note that the discussion surrounding this flag resulted in a decision that the rear-facing polygons should have flipped normal vectors (typically using gl_FrontFace to test). The schema description field mentions the normal vectors specifically.

[donmccurdy]

To be fixed soon: mrdoob/three.js#11296

Although I haven't looked into flipping normal vectors yet.

[emackey]

This appears to be fixed, thanks!