dielectric_material

Category: mental ray > Materials

Shader Family: Surface Material

Output: Color

The dielectric_material shader implements different physically-based models of reflection and refraction. It is a physically-based material shader that can simulate dielectric media such as glass, water, and other liquids.

The shader uses Fresnel's formulas for dielectric interfaces. This means that most light is transmitted through the surface for perpendicular incident directions, while most light is reflected by the surface for grazing incident angles, simulating the behavior of real dielectric materials.

The shader also uses Beer's law for absorption of light that passes through a medium. This means that the light is subject to an exponential falloff as it is transmitted between two surfaces with dielectric material.

Two types of dielectric interfaces are supported:

• Dielectric-air simulates the interface between a dielectric material and air, such as glass to air.

• Dielectric-dielectric simulates the interface between two dielectric materials, such as glass to water.

To achieve physically correct simulations it is important to use the correct surface interfaces. For example, when modeling a glass of cognac, three different interfaces are required: glass-air, glass-cognac, and cognac-air. The dielectric material uses the normals of the surface to distinguish the medium on either side of the interface.

• For a dielectric-air interface, the normals point into the air.

• For a dielectric-dielectric interface, the normals point into a dielectric material which is "outside."

To use the dielectric material, the object normals must be oriented correctly unless the ignore_normals parameter is selected.