Skinning broken for glTF 1.0 models with ModelExperimental

[lilleyse]

Several glTF 1.0 models aren't skinning or animating correctly in ModelExperimental. Interestingly the 2.0 versions of those models don't have any issues. It's possible the models were sanitized or fixed in some way before they were converted to glTF 2.0.

Ignore the missing materials - that will be addressed separately in https://github.com/CesiumGS/cesium/issues/10613.

From https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/1.0:

• BrainStem
• CesiumMan
• Monster
• RiggedFigure
• WalkingLady

[javagl]

Don't focus on the WalkingLady model. There have been several issues with that one (and... when you find yourself in a rabbit hole, you might as well learn something about rabbits - including what might be my first bugfix in CesiumJS 😁 ). I think it is now considered to be "invalid", and has been removed from the sample models repo. (The other models should work, though, but they don't appear that broken...)

[lilleyse]

Haha, I remember the WalkingLady model being one of the more problematic ones when adding support for glTF 2.0. 😄