Adding "Mosquito In Amber" glTF sample of IOR, Transmission and Volume PBR extensions

[wallabyway]

Adding glTF sample 3D model of a "Mosquito In Amber" that demostrates the IOR, KHR-materials-transmission and Volume PBR extensions, to add reflection and refraction to translucent materials.

See Press Announcement for more details: https://www.khronos.org/news/press/new-gltf-extensions-raise-the-bar-on-3d-asset-visual-realism

Model by Loïc Norgeot and mosquito scan by Geoffrey Marchal for Sketchfab licensed under CC BY 4.0

Title: "Real-time Refraction Demo: Mosquito in Amber"
Author: Sketchfab
License: CC-BY-4.0
Source: real-time-refraction-demo-mosquito-in-amber-37233d6ed84844fea1ebe88069ea58d1
Generator: "Sketchfab-7.51.0, hand-edited to add additional PBR glTF extensions."

[cx20]

For reference, I tried to display it in each library.

Library	MosquitoInAmber.gltf - front	MosquitoInAmber.gltf - another angle
glTF Sample Viewer
Three.js
Babylon.js
Filament

[cx20]

I even tried to display the same model as above with the Dassault Systèmes Enterprise PBR Sample Renderer.
However, it is almost opaque and the mosquitoes in the amber do not seem to be visible. Is this the expected result?

Library	MosquitoInAmber.gltf - front	MosquitoInAmber.gltf - another angle
Dassault path-tracer

[wallabyway]

Three, Babylon agree with ref-viewer.
@cx20 - Thank you for testing Filament and Dassault PT - I did not test those, but there looks to be a problem.
(I guess that's why we need to diversify the samples)

Next steps: We should get feedback from Filament and Dassault, to understand if the problem is on their end or on the ref-viewer side, before approving this PR.

Sound right?

[cx20]

I don't know the technical details, but this may be a problem related to KhronosGroup/glTF-Sample-Assets#65.

[cx20]

I tried to show this model again in the latest version of Filament. It looks good to me.

Library	MosquitoInAmber.gltf - front	MosquitoInAmber.gltf - another angle
Filament v1.12.0
Filament v1.12.4

[emackey]

Thanks @wallabyway and @cx20!