Further optimizes SampleModels

[sanjeetsuhag]

Optimized the glTF 2.0 models upgraded in #8539

[cesium-concierge]

Thanks for the pull request @sanjeetsuhag!

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Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[hpinkos]

@sanjeetsuhag looking at the files tab, it looks like some of these files are larger than what's in master. Is that expected?

[sanjeetsuhag]

@sanjeetsuhag looking at the files tab, it looks like some of these files are larger than what's in master. Is that expected?

@hpinkos Yes, these are minor size changes and it's just to do with the way the pipeline writes the glTF at the end.

[lilleyse]

The addDefaults stage is probably increasing the JSON size slightly, but not enough to worry about here.

This is more to get vertex cache optimizations and combining nodes/meshes/primitives to reduce draw calls.

I should be able to verify tonight.

[emackey]

Some of these models could probably benefit from PNG -> JPG conversion (when there's no alpha channel).

[emackey]

These models pass validation, and some of them have huge size savings (about 6 MB saved on this branch I think).

I'll refrain from merging because I don't know where you guys are in the release cycle today, but this looks good to me.

[lilleyse]

Looks good to me too.