Having CineRender in ArchiCAD 18 is great, that is until you want to add your own custom backgrounds to your interior renders. There is the small issue where the custom background does not display behind glass in renders as illustrated in the image below.
What causes this issue? It's simple, the standard weather presets in CineRender are apart of the Physical Sky and require a setting to turn them off, not just for the background purposes, but also for the surfaces that they might reflect or refract in.
This can be found when clicking the Detailed Settings button ➝ Environment ➝ Physical sky ➝ Compositing. Here we see 4 settings that have to do with the weather preset sky background. These 4 setting are all ticked as the default setting.
Sky Visibility, when ticked off, allows CineRender to display your custom background and still use the sun settings from the weather preset.
Sky Luminance, does not really affect your custom background image; if it is turned off, CineRender will only calculate the light from the Physical Sky, so your sky colour will not appear in your renders.
Sky Reflection, affects your reflective surfaces, turning this off will result in your surfaces not reflecting the weather preset sky.
Sky Refraction, is the important setting when working with glass surfaces and custom backgrounds, turning this off will display your custom background image through glass surfaces.
So to fix this small issue, make sure when using a custom background, that your settings look something like this.