Reflective glass unless lit from behind

[PVBergkrantz]

Hello. Is it possible to create a CineRender material like real glass, that appears almost black and reflective unless there is light coming from behind? Or perhaphs a one way mirror, reflecting from the outside but allowing light to escape from within?

[Podolsky]

I'm not sure this is possible. CineRender is not so advanced, physic-based render as new modern renders, that uses specific physical description to material behaviour. If you need more special effects - maybe try another renders like Maxwell, Octane, Felix.

[Carstenem]

This tutorial will clarify your question. It's part of my CineRender playlist

[PVBergkrantz]

Thank you for the tutorial suggestion but it does not cover anything that would answer my question.

[Erwin Edel]

The reflective properties of 'normal' glass has mostly to do with the angle it is being viewed from (refraction doing it's part).

I actually do use a very basic interior light source to tone down the reflection of the normal glass in my renders, so your basic idea is sound enough.

The basic glass from the standard template (afaik) uses both the fresnel layer from the transparency channel and the reflectance channel. I think you can turn off the fresnel part by setting fresnel reflectivity to 0%. This means you are left with the Reflectance channel: https://helpcenter.graphisoft.com/user-guide/77474/ this should offer a detailed description on how all the different settings behave.

From your general description, you probably want to have very low 'roughness' and perhaps a 'color' channel to affect the colour of the reflections (maybe something monochrome?).

If it starts to look like something you like, try dialing back up the fresnel reflectivity until you get the desired result for your camera viewpoint. Expect to play with these settings for different camera view points / angles.

I recall a fairly good tutorial to achieve something like this in Artlantis from the ebook that Dwight Atkinson wrote back in 2009, which basically boiled down by 'eyeballing' it by adjusting the refraction until you achieved the (not realistic) artistic look you wanted.

[Carstenem]

sorry wrong link! this tutorial is talking about it, start watching from around 15:40 for your glass question, hope this helps.