Is there a specular color for the particles to use with the phong render ? it looks like the rgb values are used as specular color.
Currently there isn’t. The Phong Surface scatter function makes little sense in volumetric rendering anyway, but some people (including Yours Truly) asked for it and the developers added it (reluctantly!). If you have a semi-transparent volume, each particle deeper and deeper in the volume will still produce a highlight as if it were on the surface, and this is quite unnatural. We mainly added it so that spinning particles which changing normal direction could produce sparkling effects - it was meant to be used on the Nanomintes in GI Joe The Rise Of Cobra, but the director preferred the isotropic scattering look (and I am not sure if R&H would have been able to replicate the sparkling metal look with their voxel-based approach as we had different sequences with the same look to produce).
Over time, we added per-particle channels to control the Phong SpecularLevel and SpecularPower (now available in KMY 2.3), but nobody ever asked for a dedicated specular color as the diffuse color was good enough 99% of the time.
I will log it as a Wish and see what the developers will say about it…
Using a different color for specular and diffuse components of the shader could possibly work. Like Bobo said, it’s hasn’t been something we’ve ever had to do.
There is sort of a hacky way for you to do it (to see if you like the result):
a) render1: Set Phase function to Isotropic and Color channel to your diffuse color.
b) render2: Set Phase function to Phong Surface and Color channel to your specular color.
c) Composite render1 & render2 additively.
Sort of a hack though.
(Post Edited by Bobo)
Actually, most Phong/Blinn shaders contain a diffuse component and a specular component. As Conrad suggested, you could do one non-Phong rendering for the diffuse pass and one Phong pass with a different RGB color for the specular pass and add the two.
We are discussing internally what we could do in the future to make Phase Functions work like actual shaders (so you could mix different rendering styles within the same scene in a single pass).