OpenPBR

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Is there a means to decouple specular roughness from affecting transmission/refraction? In the Standard Surface, this could be accomplished with coat roughness which did not affect the transmission roughness. In...

sharktacos

Proposal: Fuzz/sheen can darken as well as lighten

4

I’d like to propose that it would be nice if the fuzz/sheen parameter was able to darken as well as lighten. Many surface appearances such as nylon stockings, denim jeans,...

sharktacos

Better approximation for darkening layers under coat

17

Due to the possibility of total internal reflection at the coat/external medium boundary, layers under the coat should be darker. See https://graphics.cs.yale.edu/sites/default/files/wet.pdf for a detailed model describing the various effect...

AdrienHerubel

Suggest separate parameters for diffuse and metal colours instead of "base_color"

19

In the OpenPBR specification, the diffuse albedo and the metallic F0 both share the `base_color` parameter, with `base_metalness` providing the control to mix between the dielectric-base and metal substrates. We...

andre-ilm

Purpose of base_weight and specular_weight?

6

From what I can see, both of these inputs are only used as multipliers for `base_color` and `specular_color` respectively. If that is the case, they appear to be redundant, since...

lukasstockner

Add formula for the average albedo of the F82-tint model

3

It is possible to analytically calculate the average albedo of the F82-tint model used for metal reflectivity in OpenPBR. Specifically, the average Fresnel can be calculated by integrating the reflectivity...

peterkutz

Visual discontinuity at `transmission_depth` of zero

6

I'm not yet sure of the cause of this visual discontinuity, whether it's in the MaterialX graph for OpenPBR or perhaps in the real-time approximation of the MaterialX Physically Based...

jstone-lucasfilm

question regarding color value range enforcement

51

Hi. Quite excited about the work you're doing. Reading over the white paper, I noticed that the acceptable range for color values is set to be [0,1]. Does this imply...

Sam-Izdat

Emission units

29

In the emissive section it says "emissive properties are specified in photometric units", but then doesn't say what units they're actually specified in. Assuming this means nits, this should be...

anderslanglands

Should non-physical tinting affect lower layers?

3

The spec currently mentions that if `specular_color` is used to affect the color of the specular reflection, he underlying layers (diffuse/SSS/transmission) should be tinted according to the complementary color to...

lukasstockner