Lighting & rendering · Intermediate

Index of refraction

The number that sets how much glass, water and gems bend light

Also called IOR

What is the index of refraction?

The index of refraction, or IOR, is a number that says how much a clear material bends light passing into it. Air is about 1.0, water about 1.33 and ordinary glass about 1.5. In 3D, it sets how glass and liquids distort what is behind them, and how strongly surfaces reflect.

Think of it like this

It is like walking from pavement onto sand at an angle: you slow down and your path turns slightly. A higher IOR is deeper sand.

Where it fits in a 3D project

  1. Create
  2. Surface
  3. Rig
  4. Animate
  5. Render
  6. Export

Surface: Giving the shape its color and material: UVs, textures and shaders.

How the index of refraction works

  1. 01Light crosses from one material into another, such as air into glass.
  2. 02It slows down inside the denser material, which bends its path.
  3. 03The higher the IOR, the more it bends and the more the surface reflects.
  4. 04The renderer uses the value to draw distortion through glass and water.

Where the index of refraction is used

  • Glass, water and ice
  • Gems and jewelry with sparkle
  • Reflection strength in PBR materials

Beginner tip

Keep IOR realistic. Raising it to make glass more dramatic usually makes it look like plastic or crystal instead; try changing the lighting or background first.

Terms related to the index of refraction

Index of refraction FAQ

What is IOR in 3D?
IOR is short for index of refraction. It is a material setting that controls how much light bends through transparent objects and how reflective surfaces look, through the Fresnel effect.
What is the IOR of glass?
Ordinary window glass is about 1.5, which is a good default. Denser glass and crystal go higher, roughly 1.6 to 1.9.
What are common IOR values?
Roughly: air 1.0, ice 1.31, water 1.33, glass 1.5, most plastics 1.45 to 1.6, and diamond 2.42. Opaque materials such as wood or fabric are usually left near 1.5 in PBR shaders.
Does IOR matter for opaque materials?
A little. It still sets how strongly the surface reflects at glancing angles. Most PBR shaders use a sensible default, so you only change it for clear or very shiny materials.

Updated October 29, 2026 · Browse all 3D terms