What type of glass should I use?
There are two glass rendering modes in the Refraction section of the standard Corona Material. They should be used for setting up glass in different scenarios:
-
"Thin (no refraction)" checkbox enabled - such material does not refract light and does not generate refractive caustics, which makes it render very fast. This mode should be used for very thin objects such as glass panes in windows, soap bubbles, light bulbs.
- "Thin (no refraction)" checkbox disabled - such material generates refraction and should be used for solid objects such as vases, glass furniture, glass objects with absorption color, liquids. You can toggle refractive caustics for this mode, however, enabling caustics will always make rendering much slower.

Examples
"Thin (no refraction)" checkbox enabled
"Thin (no refraction)" checkbox disabled, caustics disabled (transparent shadows)
"Thin (no refraction)" checkbox disabled, max sample intensity = 20
"Thin (no refraction)" checkbox disabled, max sample intensity = 0
"Thin (no refraction)" checkbox disabled
"Thin (no refraction)" checkbox disabled