Thick foil interface law



Specular material with no bulk medium and a foil law with 0.1mm blue polymer medium

Interface law The Foil interface law is similar to the Fresnel interface law, but it adds a dielectric foil at the interface. The refractive indices of scene media located in front and behind the surface are taken into account, as well as the properties of the layer. The latter is defined by an internal medium defined in the law element, and a thickness.

The polarization state of light is computed accurately by this law.

The differences with the Thin film interface law are

  • It uses incoherent optics instead of coherent optics in the layer. Therefore, it is more suited for layers of 0.1mm or above.
  • It takes into account only the real part of the layer refractive index for interface reflections. The imaginary part is only used for absorption through the layer thickness. Therefore, it is suited only for dielectric layers for which k is negligible in front of n.

This law is well suited for flat glass sheets, polymer foils, liquid films, etc...

Children Nodes

Medium medium The foil medium


name type description
thickness real The foil thickness in meters

Ocean XML 3.0 example

<intlaw name="intlaw" type="foil">
   <medium name="medium" type="simple">
      <spectrum name="n" type="uniform" value="1.5235"/>
      <spectrum name="a" type="rgb" rgb="5000 4000 2000" gamma="1"/>
   <prm thickness="0.0001"/>