Refractive Index

Refractive Index is a material parameter that is found in multiple KeyShot material types. The term might not be familiar, but refraction is something that is seen every day. A good example is when a person sticks their hand in a pool. The light is bent, or “refracted” and the arm looks broken.

Refraction occurs because light travels through different media at different speeds. This reduction in speed is referred to as a material’s refractive index (or index of refraction) and is represented by a number. For example, water has an index of refraction of 1.33, glass has an index of refraction of 1.5 and diamonds have an index of refraction of 2.4. This means that light travels through water 1.33 times slower than it does through a vacuum. Light travels through glass 1.5 times slower, through diamonds 2.4 times slower and so on. The slower light travels, the more it is bent and distorted.

Refractive indices for different materials can be easily found online. Once the value is found, it may be entered into the Refractive Index property of a material, and will be accurately represented in KeyShot.


Caustics is the pattern of light and color that occur when light rays are refracted or reflected. In everyday life you encounter caustics when you for example place a glass of water on a table.

Known issues

Caustics will now work inherently with volumes (e.g. scattering media), however, caustics will only be applied to light sources outside the volume and this is only supported in in interior mode.