Real-time glass, in five terms.
Iridescence — a film thinner than a wavelength sits on the surface, so the colour of a reflection drifts from green to violet as the angle changes, like oil on water.
Index of refraction — how sharply light bends as it crosses into the material: about 1.33 for water, 1.5 for window glass, 2.4 for diamond.
Dispersion — the index differs for each wavelength, so a single bevel splits white light into a faint spectrum along its edge.
Transmission — the share of light that passes through the body instead of bouncing off it, before thickness and tint absorb part of it.
Roughness — microscopic scratches that spread reflections and refractions, from mirror-polished to frosted.