Skip to content

Index of Refraction (IOR)

glTF extension: KHR_materials_ior
glTF property: ior

Index of Refraction controls how light bends when entering the material. IOR is a scalar constant — there is no texture input. The glTF default is 1.5; the extension is only written when the value differs from that default.

Shader Attribute Minimum
standardSurface, aiStandardSurface specularIOR 1.0 (clamped)
openPBRSurface specularIOR 1.0 (clamped)
StingrayPBS not supported —

Setting IOR

Set specularIOR directly on the shader. The exporter reads the value and clamps it to a minimum of 1.0 (values below 1.0 are physically invalid and are raised to 1.0 before export).

Exports as ior inside the KHR_materials_ior extension object.

Note

The glTF default for ior is 1.5. The extension block is omitted entirely when the exported value equals 1.5, so setting specularIOR to 1.5 produces the same result as leaving the extension off.

Notes

  • IOR is scalar only — there is no texture slot for this property in glTF.
  • Values below 1.0 are clamped to 1.0 before export.
  • The KHR_materials_ior extension is only written when ior ≠ 1.5.
  • Both standardSurface/aiStandardSurface and openPBRSurface use the same attribute name (specularIOR).
  • StingrayPBS does not export KHR_materials_ior.