Hair: transmission in specular

[sharktacos]

The options for the VrayHair3Mtl have a "transmission in specular" checkbox. This is not mentioned in the docs. How is this intended to work? I would expect this to mean that the transmission result would be in the spec RE instead of the in the refraction RE, but it appears that the refraction RE is unchanged and there is additional transmission in the spec, which results in the render elements not adding up the beauty.

[yolov]

This seems to work for me in a simple test. Can you share a scene that we can look at? What V-Ray version are you using?

I'll add this to the documentation.

[sharktacos]

Let me be more specific about the results I am seeing:
With "transmission in specular" ON I see more from the transmission in the specular RE, however comping lightingRE+SpecularRE+reflectionRE does not equal the Beauty. I would expect to see all of the transmisson in the specRE instead of in the RefractionRE with this option on. The refractionRE however is unchanged whether this option is on or off. The spec is changed, but it does not get the full transmission, just a portion of this.

Are you getting different results? I have attached a simple scene showing this hairTransmSpec.zip

[yolov]

Here's the results I'm getting (attached to this post):

I've rendered with "transmission in specular" enabled and disabled. When the option is enabled vs. disabled - I made a diff between the refraction channels when, a diff between the specular channels, and then a diff of those two diffs. The diff of the diffs shows some very slight differences which I've made visible by applying a gain of 10, otherwise they're too subtle to spot. Is this what you're referring to as a difference in the comp or is it something else. If it's something else, can you please send us an image so we get a better visual idea?

[sharktacos]

Hi Alex,
Yes I get the same results. I would expect that with the "transmission in specular" ON I would get 100% of the transmission from the shader in the specularRE so that the refraction RE could be excluded from the comp, and one would only need to add lightingRE+SpecularRE+reflectionRE to get the full beauty in comp for the material. The behavior of getting a small portion of the transmission in the specularRE doesn't make much sense to me. It would be very useful however to have an option to get 100% of the transmission in the specularRE

[yolov]

OK, let me get a word from the devs and I'll get back to you as soon as I can.

[Mihail.Djurev]

I can confirm that the transmission coming from GI is included in the refractionRE even if "transmission in specular" is ON.
We are currently testing a fix for this.