Support transmission in translation from Standard Surface to glTF PBR

[charo-m]

This corrects the translation of transmission parameters from Standard Surface to glTF PBR.
Issue: #1599

Here's the change in a more readable pseudocode:

if (transmission > 0) {
    if (transmission_depth > 0) {
        attenuation_color = transmission_color
        base_color = white
    } else {
       attenuation color = white
       base_color = transmission_color
    }
} else {
    attenuation_color = white (default)
    base_color = no_transmission_base_color (hasCoatColor ? mixedBaseColor : scaledBaseColor)
}

Before ->

After ->

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: charo-m / name: Charlotte Manning (3b9f582, 975a52e)
• ✅ login: jstone-lucasfilm / name: Jonathan Stone (2780c87, 81c8911, fccb792, be8d624, dfa8420, a6479ae)

[jstone-lucasfilm]

@charo-m This looks really promising, and to resolve the EasyCLA issue, I'd recommend following up through the support link that the Linux Foundation provides:

https://jira.linuxfoundation.org/servicedesk/customer/portal/4

[charo-m]

thanks @jstone-lucasfilm ! I had a mismatching email address, just managed to get my CLA signed.

[jstone-lucasfilm]

@charo-m Excellent! Sometimes the LFX needs to bump the EasyCLA check so that it updates to your new email address, so feel free to check with them if it doesn't automatically turn from red to green.

[kwokcb]

As a suggestion, it might might be better test to have the graph with the translation node in it to be able to do visual compares as part of the render test suite. Perhaps it be added to the test suite in a new folder resources/Materials/TestSuite/pbrlib/translation. ( @jstone-lucasfilm, I don't see any other translation examples anywhere else ? Others could be added in as desired).

[kwokcb]

Add @emackey here to double check the logic.

[jstone-lucasfilm]

This looks really good, thanks @charo-m, and I had just two recommendations for improvements.

[jstone-lucasfilm]

Thanks for these updates, @charo-m!

For now, I think it's fine to omit the new standard_surface_to_gltf_pbr_glass.mtlx unit test, which is an interesting suggestion for a future improvement to our translation system, but not an update that we need as part of your Dev Days project.

[jstone-lucasfilm]

Great work on this improvement, thanks @charo-m!