What is it?
Some refractive materials change the direction in which light travels inside them by a different amount depending on the wavelength of the light. This is called dispersion and creates a rainbow effect inside the material. Enabling it adds realism to gemstones, glass, water, other liquids, and other materials.
How to enable it?
Dispersion can be enabled for any refractive Corona Physical Material by ticking the "Enabled" checkbox under its refraction properties. The Abbe number value controls how strong the dispersion effect is. Values between 30 and 60 should be used for most realistic materials. For Corona Renderer 5 and older, the minimum Abbe number value is 20. For Corona Renderer 6 and newer, it can be lowered to 1, producing an extremely strong rainbow effect.
Pool with caustics. Dispersion disabled.
Pool with caustics. Dispersion enabled and Abbe number set to 20. Note that caustics are also affected by dispersion.
Pool with caustics. Dispersion enabled and Abbe number lowered to 5 to exaggerate the dispersion effect. Note that caustics are also affected by dispersion.
Diamond ring. Dispersion disabled.
Diamond ring. Dispersion enabled.