Develop/gltf sample viewer enhancements

[UX3D-haertl]

This PR adds models which were previously used for the sample viewer

[donmccurdy]

Seeing a number of 4K textures containing just a solid color here – would it be possible to swap those for a factor?

[cx20]

Some models seem to have cases where the file name differs from the folder name. Following convention, it is more consistent to match file and folder names. Since SheenChair already exists, it would be better to place it in a different folder.

Below are the proposed changes.

before	after
ClearcoatRing/glTF/PBR - Metallic Roughness Alpha-blend.gltf	ClearcoatRing/glTF/ClearcoatRing.gltf
SheenChair/glTF/gltf_sheen_damask.gltf	SheenDamask/glTF/SheenDamask.gltf

[UX3D-haertl]

I transformed the base color and emissive textures to factors and renamed to assets as suggested

[cx20]

@UX3D-haertl Thank you for the improvement.
I think the readme and screenshot also need to be added.

Model Nmae	README.md	screenshot
ClearcoatRing	⚠️ Link Error	✅
ClearcoatSphere	❌	❌
SheenDamask	❌	❌
SheenHighHeel	❌	✅
TransmissionSuzanne	❌	❌

[cx20]

I experimentally tried the ClearcoatRing model with gltf-test.
However, the display result of each library seems to be different.
I could not determine if the problem with the see-through back was a model problem or a library problem.

[cx20]

I also checked SheenDamask. This model seems to look quite different from library to library when viewed from an angle.

[donmccurdy]

However, the display result of each library [for ClearcoatRing] seems to be different.

The ClearcoatRing materials are all using "alphaMode": "BLEND" — I think that would be a mistake in this case.

[cx20]

@donmccurdy Thank you for your advice.
I tried removing the alphaMode property of the material locally to test it out.

https://github.com/KhronosGroup/glTF-Sample-Models/blob/develop/gltf-sample-viewer-enhancements/2.0/ClearcoatRing/glTF/ClearcoatRing.gltf#L244

Results appear to be good.

[DRx3D]

The automated validation failed. We would like to get this merged in the next week if everything is clean and good to go.

[DRx3D]

@echadwick-wayfair , @emackey : Please make a final review of the models

[DRx3D]

@UX3D-haertl : Except for the conflict with model-index.json, is this PR ready to go?

[UX3D-haertl]

Yes it is ready from my side