GLTFLoader: Revert usage of computeTangents().

[Mugen87]

Related issue: #11438 (comment)

Description

It seems computing tangents currently breaks NormalTangentTest test asset. Reverting the change solves the issue for now.

I guess we have to find another way to fix double sided rendered models.

[donmccurdy]

Thanks!

I'm looking into the original issue a bit more now.

[mrdoob]

Thanks!

[WestLangley]

It seems computing tangents currently breaks NormalTangentTest test asset.

Calling computeTangents() outside the loader works fine.

When tangents are computed by the loader, this code block is executed, which flips normalScale.y.

/ping @elalish

[donmccurdy]

I've added an option generating MikkTSpace vertex tangents for any glTF file with an offline CLI here: https://gltf-transform.donmccurdy.com/cli.html ... for example:

gltf-transform tangents input.glb output.glb

It works on the web too (using WebAssembly) but MikkTSpace requires unwelding mesh vertices, so — similar to this PR — it's probably not something that we'd want to automatically apply to all glTF files.