Implement tangent computation for OBJ loading

[GrantMoyer]

Issue #266

I went ahead and implemented indiscriminate tangent computation during OBJ file loading. I should be relatively straightforward to convert it to one of the other options mention in the issue if that's desirable.

[GrantMoyer]

This effectively loads per face tangents, since it computes tangents per tri without respect to neighboring tri's. The most straightforward way to compute per vertex tangents probably involves implementing proper indexing instead of duplicating shared vertices.

[GrantMoyer]

Okay, this should now compute per vertex tangents. They should still probably be weighted by face area or some other method.

[fu5ha]

You could use this crate, mikktspace is pretty standard as a very effective tangent space now. https://github.com/gltf-rs/mikktspace

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On Sun, Feb 9, 2020, 10:13 AM Grant Moyer ***@***.***> wrote: Okay, this should now compute per vertex tangents. They should still probably be weighted by face area or some other method. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#267?email_source=notifications&email_token=AAGYXHYVEGGVZJ4UBMW6KELRCA2UXA5CNFSM4KRX23IKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOELGSIZQ#issuecomment-583869542>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAGYXH4UEYLCUBPDGCTJIZDRCA2UXANCNFSM4KRX23IA> .

[GrantMoyer]

Thanks for the pointer. I was surprised how non-standardized tangent space computation was when I looked into it. I'm marking this ready for review now.

[GrantMoyer]

Is there anything blocking this that I could fix or help with?