This especially being since the new Multiscatter GGX is literally the only way to get correct results as far as glossiness/glass rendering is concerned.
The idea would assume, first of all, that the Beckmann shading model would disappear from the Glossy, Anisotropic, and Glass nodes. This in turn would be replaced by a new value that allows the user to control the length of the specular tail for GGX shading (a value of 0 for instance would mean a quick termination akin to Beckmann and values of 2 and above would mean a very slow decay).
In general, having such control would be nice because I can see shading uses for very low and very high values, a very low value for instance can give a ‘fatter’ look to the shading while a very high value could be useful for cloth/textile effects. In addition, having this control replace Beckmann shading would mean less Kernel pressure for GPU users (since we essentially swap one feature for a much better one).
For more details, here’s a visual idea as to how the specular tail control could be mapped
Yes Lukas, it’s just that GTR provides the same results as GGX, in case of Vray with a tail of 2.0. Whether it’s useful or not, from an artist standpoint I can say it is, but not necessarily a must, especially if the implementation is not simple/straightforward. The new Multiscatter GGX is far more important, IMHO.
From my understanding, setting the tail control to a very low value would give you something quite similar to Beckmann (but with the advantage of being able to have everything in between as well and then some).
The idea would be that the tail control would be integrated as a part of the new multiscatter model (along with the original GGX shader), and not as a separate shading algorithm.
