Alain Martel <kua### [at] videotronca> wrote:

> > Whenever I create a scene that contains objects made of glass, I spend a lot of
> > time tweaking the various pigment, finish, and interior parameters of the
> > material to try and get something that looks realistic.  Sometimes I start with
> > what I can find in glass.inc, but it doesn't appear to have been updated since
> > v3.5.
> >
> > Has anyone worked on something similar to RC3Metal for glass that takes
> > advantage of all of the new finish features in later versions?  It might be
> > something I'd be willing to explore, but I don't have a great grasp on how all
> > of combinations, including fresnel interact, so it's going to be hit and miss.
> >
> > Thanks,
> >
> > -- Chris R.
> >
> >
>
> Normally, for a transparent object having an IOR, you use reflection{1
> fresnel} to control the reflectivity. There is usually no need to use
> another value here.
> Fresnel reflection depends entirely on the ratio between the ior on each
> sides of the surface and the angle of incidence. A ratio of 1 mean NO
> reflection. A standalone object without an interior defining an ior
> different from 1 will also show no fresnel reflection.
>
> When the fresnel keyword is present, it always default to ON.
> falloff and exponent should be left to their default values. Don't use
> those.
> Do not use metallic.
>
> Then, you should also use the fresnel option for the highlights. Need
> the latest version. IIRC, it was not implemented in version 3.7, but is
> supported in the latest V1.8 beta.
> Examples : specular 0.7 fresnel roughness 0.001, phong 0.7 fresnel
> phong_size 500
>
> Also, you should use transmit 1 or filter 1 as your pigment.
> If you want the object to be coloured, use fading in the interior
> statement :
> interior{ior 1.5 fade_color rgb<1, 0.6, 0.6> fade_distance 1 fade_power
> 1001}// A pink object.
> Adjust fade_distance for the dimension and scale of your object. It's
> easily the most important parameter when using fading colours in an
> interior.
>
> ALWAYS use conserve_energy.
>
> Sample glass :
> texture{
>  pigment{rgbt 1}
>  finish{specular 1 roughness 0.001 fresnel
>   ambient 0 diffuse 0
>   reflection{ 1 fresnel }
>   conserve_energy
>  }
> }
> interior{ ior 1.5 //typical glass IOR
>  fade_color rgb<0.9, 1, 0.9>//slightly greenish
>  fade_distance 2 // Adjust to the size and scale of the object
>  fade_power 1001}

Thanks for the insights.  I am trying them out now.

I don't have a good understanding of when to use the albedo keywork for specular
and diffuse reflection.  I note that you do not use it above.

-- Chris R.

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