Vertexix

OpenPBR Shading

· · Ultra

Shading Model, in PBR Settings, switches PBR Preview between two different renderers for the same material data: the default Cook-Torrance shader (see PBR View), and Adobe's OpenPBR BSDF — a real, layered physically-based shading model rather than glTF's additive extension set. This is an alternative to try alongside the default shader, not a replacement for it — nothing about your imported materials, textures or bakes changes either way. OpenPBR shading is gated to Ultra edition.

The same model rendered in PBR View with OpenPBR shading turned on, lit by an HDR environment
A model in PBR View with OpenPBR shading on, under the same HDR environment as the default shader.

Turning it on

Open PBR Settings (Shift+P while PBR Preview is on) and expand the Shading Model section, between Emission Light and Image Based Lighting. Use OpenPBR shading is unavailable until PBR Preview itself is on — the checkbox is disabled with a tooltip explaining why until then.

What changes

The same imported material values — base color, metallic, roughness, and every KHR_materials_* extension Vertexix reads (specular, sheen, clearcoat, anisotropy, transmission & volume, iridescence, dispersion) — feed OpenPBR's own equivalent layers (fuzz from sheen, coat from clearcoat, thin-film from iridescence, and so on) instead of the default shader's additive Cook-Torrance terms. The practical difference is most visible on materials that actually use one of those layers; a plain metallic-roughness material with none of them will look close to identical between the two shaders, since both are physically-based microfacet models converging on similar answers for the same simple inputs.

Directional Light is evaluated through the real OpenPBR BSDF either way. Image-based lighting is currently an approximation that reuses the same environment maps the default shader uses, rather than a fully layer-accurate OpenPBR environment response — expect the directly-lit side of a material to show OpenPBR's layering most clearly.

Current limits

OpenPBR shading works from the same material data every import already provides — it doesn't add new import capability. True subsurface scattering isn't available (nothing in Vertexix's import pipeline supplies it yet), materials still come from your file's own glTF-style data rather than an authored OpenPBR/MaterialX file, and PBR Layer View's debug channels are specific to the default shader and aren't available while OpenPBR shading is on.