Skinning broken with log depth

[bagnell]

Using log depth when skinning shows artifacts.

The current model implementation has a workaround until it is fixed. To see the issue, remove the two lines here.

[bagnell]

Babylon.js has the same issue. I think it's an issue with the model.

BabylonJS/Babylon.js#4240

[emackey]

I'm not convinced it's an issue with the model, because it only happens when Log Depth is enabled.

[emackey]

Update: It is indeed believed to be the fault of the model, for not having normalized bone weights. See KhronosGroup/glTF#1213 (comment)

[lilleyse]

Also came up in #8875 with this model: miner.zip