Screenshot from UX3D glTF Sample Viewer with the environment Wide Street, environment rotation set to -Z, and the ACES (Hill) tonemapper.
This asset demonstrates the use of KHR_materials_diffuse_transmission to represent thin-surface transmission of light through a thin ceramic teacup and saucer.
With the extension, versus without it.
The ingredients used for Diffuse Transmission: diffuseTransmissionColorFactor, and diffuseTransmissionFactor.