Индкс преломления зависит от материала, который нужно симулировать.
Reflection color (цвет отражения)
Цвет света, отражаемого от поверхности.
This is the color that light will be filtered to after being transmitted. For perfectly clear glass, set both reflection and transmission colors to 1.0. The color given here will be applied to the material uniformly, you may wish to derive the color from the objects volume instead. (or use the glass2 material, which uses the volume for nearly everything)
This is the B value to Cauchy's equation. (The value specified under IOR will be used for n) Setting this to anything other than 0 will enable chromatic dispersion, aka splitting the spectrum into a rainbow of colors. Be warned this is an intensive effect that will greatly increase the number of samples (and photons, if applicable) that are needed!
This option disables refraction during transmission. The effective result is that transmission will appear as though the glass had an IOR of 1.0, while reflections will use the specified IOR. The resulting glass will show only the transmission/reflection colors, volumes effects, and reflections, and is not terribly realistic. However, it won't look much different for a thin sheet of glass such as a window, and it will render much faster, as there is less to compute.
There are several other important features to architectural mode, besides reducing the necessary calculations of the material. Because there is no refraction during transmission, architectural glass is transparent to shadow rays and alpha, neither of which is the case in non-architectural mode. This is especially important for window glass. Because it is transparent to shadow rays, it is possible to perform direct light sampling through the window to outside light sources, greatly improving the render efficiency. And because it reflects but still propagates alpha, it allows you to have realistic interior reflections and absorption on the windows, while still being able to composite in a backdrop for the view outside of the window.
Thin Film (тонкая плёнка)
Определяет плёнку, покрывающую поверхность. Обычно это приводит к радужным отражениям. Есть две настройки: depth (глубина) и IOR. IOR должен соответствовать материалу, который вы собираетесь симулировать.
Glass vs Glass2
В LuxRender также есть материал Glass2, который functions essentially as an "empty shell" for a volume. This volume then gives the material its IOR, as well colors in the form of absorption and scattering. It is important to remember that the Glass material can use volumes for absorption and scattering as well, it will simply use its own IOR value, and the reflection and transmission colors will still be used. This is the same way you would use volumes with the other trasparent/translucent materials.
In most cases, Glass and Glass2 will be similar in appearance, given the same volume, and IOR settings on the Glass material and the volume being similar. However, Glass2 can accurately calculate the relative index of refraction between two surfaces (such as water in a glass), which Glass requires to be done manually with a 3rd mesh and the user calculating the relative IOR value by hand. The volume system allows for its mediums to be given more specific and technical IOR data than the Glass material, such as using the Sellmeier equation, so Glass2 technically can handle light more accurately than Glass.
On the other hand, since the Glass2 material does not define its own surface, it lacks the Glass material's option for things such as a separate reflection color (for painted surfaces) or using a thin film coating. Depending on your exporter, it may also be more work to set up Glass2 when you just want some generic glassy surface for an object off to the side of the frame.