labPBR support

[jackjt8]

labPBR provides a standardised PBR format which is primarily used to end fragmentation for shader and resource packs. At the time of writing there 13 Shaders and 4 Packs which support the labPBR specification and have been approved.

labPBR Format Wiki

Key features:

Normalmaps (with the _n suffix):
Red - n/a
Green - n/a
Blue - Material Ambient Occlusion
Alpha - Heightmap (POM)

Specularmaps (with the _s suffix):
Red - "perceptual" smoothness (related to linear roughness)
Green - F0 / reflectance : Store linearly 0 to 229 (90%). 230 to 255 represent various different metals. For a value of 255 the albedo should be used.
Blue - On dielectrics store porosity for 0 to 64, and 65 to 225 for subsurface-scattering.
(On metals is reserved)
Alpha - Emissiveness

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Not only would this mean that we have access to a number of premade PBR resource packs, but we would be able to cross check implementations in Chunky against a multitude of Shaderpacks. Use of a standardised PBR implementation is beneficial over a custom implementation as it reduces fragmentation and improves cross compatibility.

[Continous]

It should be noted that the 230-255 represented metals is also defined in the specification.

230 - Iron
231 - Gold
232 - Aluminum
233 - Chrome
234 - Copper
235 - Lead
236 - Platinum
237 - Silver

This is useful since it would allow Chunky to implement hard-coded real-world values for the material behaviors of these metals. There's also an addition 18 slots remaining for other metals as more become more prominent and common within the game.