Build an OpenPbrMaterial that reproduces pbr's shading as closely as
the OpenPBR Surface model allows.
Mapping — base/specular/coat/fuzz/thin-film/subsurface/anisotropy/emission
all transfer 1:1 in meaning (only the parameterization differs); the dielectric
specular scalar + ior collapse into OpenPBR's specular_ior + specular_weight
so the resulting base F0 is identical (0.08·specular·specularColor). Textures
carried: base-color, normal, metallic-roughness (engine MER), emissive,
anisotropy (direction/strength).
Carried: per-texture UV transforms (KHR_texture_transform) — both the
per-texture table and the single shared transform (replicated into every slot,
since OpenPBR has no shared/atlas UV path). The engine atlas uvTile is dropped
(glTF content never sets it).
Not carried (no OpenPbrMaterial equivalent yet — falls back to the constant
factors, or is dropped): the per-pixel extMap (deferred clearcoat/sheen/
iridescence multipliers); texCoordMask (second UV set); alphaCutoff
(no OpenPBR alpha-test yet); clearcoatNormalToGeometric; clothWrap.
Refractive transmission (transmission, thickness, attenuation*,
dispersion + the transmission/thickness maps) IS carried — rendered by the
forward TransmissionPass, which now reads either material.
Build an OpenPbrMaterial that reproduces
pbr's shading as closely as the OpenPBR Surface model allows.Mapping — base/specular/coat/fuzz/thin-film/subsurface/anisotropy/emission all transfer 1:1 in meaning (only the parameterization differs); the dielectric
specularscalar +iorcollapse into OpenPBR'sspecular_ior+specular_weightso the resulting base F0 is identical (0.08·specular·specularColor). Textures carried: base-color, normal, metallic-roughness (engine MER), emissive, anisotropy (direction/strength).Carried: per-texture UV transforms (
KHR_texture_transform) — both the per-texture table and the single shared transform (replicated into every slot, since OpenPBR has no shared/atlas UV path). The engine atlasuvTileis dropped (glTF content never sets it).Not carried (no OpenPbrMaterial equivalent yet — falls back to the constant factors, or is dropped): the per-pixel
extMap(deferred clearcoat/sheen/ iridescence multipliers);texCoordMask(second UV set);alphaCutoff(no OpenPBR alpha-test yet);clearcoatNormalToGeometric;clothWrap. Refractive transmission (transmission,thickness,attenuation*,dispersion+ the transmission/thickness maps) IS carried — rendered by the forward TransmissionPass, which now reads either material.