Examples of good good glass reflections in Unity mobile game?

Stu2Prof

Hi guys

I am currently studying an MA in Games Art and am looking to recreate this room from Ex Machina in a mobile games project. The view point will be from the protagonists point of view looking at Ava. My tutor is concerned that the quality of the end result will be lowered because glass in Unity on mobile doesnt produce reflections and takes a lot of power. Could anyone provide me some good examples of glass reflections in a working mobile game?

My other option is taking on a very graphics intensive detailed scene that I am worried may be a bit messy.

Eric Chadwick

Mobile games usually can't handle the performance requirements of real-time reflections.

The glass reflection is usually done by rendering the scene a 2nd time, storing that in a new texture, and mapping it in screen space back onto the glass. The extra rendering slows things down, and the new texture hogs memory.

You can optimize the 2nd rendering by hiding things unseen by the glass, simplifying the shaders of reflected things, removing small things from being rendered, only updating the 2nd render every few frames, reducing the 2nd render resolution, etc. But it's still a big hog.

A lot of mobile games use the old-school technique of flipping the entire scene and putting it behind the glass, then rendering it with a bit of transparency. The first Duke Nukem famously did this. 
https://www.quora.com/Why-do-so-many-video-games-have-an-aversion-to-using-working-mirrors-in-their-environments
That way the whole scene is rendered in one go. But this wouldn't work in your case since the part behind the glass isn't covered on the sides.

I would just use a baked reflection probe, and not render the character in the reflection. This is a mobile game after all.
https://docs.unity3d.com/Manual/ReflectionProbes.html

Stu2Prof

Thanks so much for that advice. I was thinking of a cube map for this. Would the reflection probe still present a problem for rendering on a mobile device?

Eric Chadwick

Nope, should be fine as long as you set it to baked, not realtime.

Realtime means it re-renders dynamically, which would likely cause a significant performance drop. Cube is 6 renders.

Stu2Prof

Thanks Eric!