Category: mental ray > Materials
Shader Family: Surface Material
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.
| Name |
The name of the shader node displayed in the render tree. Enter any name you like, or leave the default. |
| col |
The "persistence" coefficient that corresponds to the fraction of light which is left after traversing one unit of material. A value of 0.9 means that 10% of the light is absorbed per unit length of the material. Lengths are measured in world coordinates. |
| ior |
The index of refraction of the dielectric material. |
| col_out |
If selected, the material is a dielectric-dielectric interface and this parameter is the persistence coefficient of the outside dielectric material. |
| ior_out |
Used in combination with col_out to describe the outside dielectric material. |
| ignore normals |
The decision of whether a ray enters or leaves the object is usually based on the direction of the normal (towards or away from the incident ray). If the object is poorly modeled and the normals are not useful for this calculation, selecting this option makes the dielectric material shader count the number of times the ray has entered and left the object instead of relying on the normal direction. |
| phong coef |
A Phong coefficient used to compute normalized Phong highlights which is used to generate a false impression of an area light source. If this value is zero, there are no false highlights, and only the reflected rays can create highlight effects if they hit something bright. |
| mode |
The mode selector for the light list. For more information, see Setting the Light List Mode [Direct Illumination]. |
Creates a light list to specifiy which lights should produce the effect. For more information, see Using Light Lists [Direct Illumination].
