Shading the Macbeth chart in Arnold - lambert or other shader?

Trying to clean up a pipeline and bumped into this one - to use the Macbeth chart in scenes for asset creation etc. would we need to use a lambert shader or something else?

It seems when using just standard surface, there is too much added variation from specular and other values.

So, what’s the correct way to use the chart?

Thank.

Lambertian-like shader would be fine, you could use the Standard surface and remove the specular contribution.

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So as long as it’s a super matter shader with no specular, we should be fine , right ?

Are there any caveats, worse or better ways rendering the chart ? Wanna eliminate mistakes as much as possible.

Cheers,
v

Yes but keep in mind that the values of the ColorChecker Classic are always given for a particular geometry, typically 0:45 or 45:0: Color Measurement Instrument Geometries

Should we really remove all specular contribution ?
I learned at some point that real-world macbeth are not perfectly rough objects and still have a tiny specular contribution.
Assuming the use-case is to match a real-world macbeth and not just ensuring consistency between full cg shots.

Yeah, I agree.

I often share this link to my team: https://filmicworlds.com/blog/everything-has-fresnel/

Also I have “forbidden” the use of Lambert on the show. It is the Arnold Standard Surface all the way. :wink:

Regards,
Chris

Unless you have measured the BRDF of a colour rendition chart, which intensity value are you going to use for specular, which glossiness?

Worth pointing out that Arnold Standard Surface diffuse reflection component is Lambertian by default.

I cannot argue the specular values I pick are accurate as they are eye-based. But I do full cg shot so I only ensure all renders have the same macbeth configuration for consistency.
If you do have some measurements I’ll be very curious !