The Refraction BSDF is used to add glossy refraction with sharp or microfacet distribution, used for materials that transmit light. For best results this node should be considered as a building block and not be used on its own, but rather mixed with a glossy node using a Fresnel factor. Otherwise it will give quite dark results at the edges for glossy refraction.
Color of the surface, or physically speaking, the probability that light is refracted for each wavelength.
Influences sharpness of the refraction; perfectly sharp at 0.0 and smoother with higher values.
Normal used for shading; if nothing is connected the default shading normal is used.
Microfacet distribution to use. Sharp results in perfectly sharp refractions, while Beckmann and GGX can use the Roughness input for blurry refractions.
Standard shader output.