Material

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Materials control the optical properties of geometry surfaces, such as reflectance, glossiness, roughness, transparency or light emittance.

When exporting the scene from a CAD software, each surface is given a material name. Some basic materials (generally diffuse) with the matching names are created in the process. After loading the scene in Ocean, you can edit these materials, to give them more realistic properties. You can also link them to existing materials, or import previously exported Ocean materials.





Lambertian

Example of an ochre lambertian material

Summary

This material type follows the Lambertian reflectance model. The apparent brightness of such a surface to an observer is the same regardless of the observer's angle of view. This simple model describes efficiently diffuse surfaces, but more complex models such as Oren-Nayar material or Phong material will describe better very rough and slightly reflective materials, respectively.

Link

Lambertian material reference

Specular

Example of a specular soda-lime glass material

Summary

This model corresponds to perfectly smooth reflective and refractive materials. A ray of light with a given wavelength will exit the surface with only two possible directions : mirror reflection and refraction. No scattering occurs, in other terms, this is a pure dirac BRDF

Specular materials are often used with a bulk medium : this means they do not describe only surface properties, but also what happens to light within their volume. The medium associated to the material governs refraction, and volumetric light extinction.

Reflection and transmission coefficients are governed by the defined interface law. This can range from simple fresnel law (assuming the material is a simple diopter between bulk and external medium) to complex optical surfaces.

Link

Specular material reference

Reflective

Example of reflective material with rough copper properties

Summary

This model describes reflective opaque surfaces. It uses a roughness model for describing the slope distribution, and an interface law for the spectral reflection coefficient. The combination of both allows describing a very broad variety of materials.

For modelling a transparent surface, please refer to rough transparent and specular types.

Link

Reflective material reference

Rough transparent

Example of rough transparent material with sandblasted glass properties

Summary

This model corresponds to rough reflective and refractive materials. It works similarly to the specular material type, except the surface is rough, and causes scattering.

Rough transparent materials are often used with a bulk medium : this means they do not describe only surface properties, but also what happens to light within their volume. The medium associated to the material governs refraction, and volumetric light extinction.

Reflection and transmission coefficients are governed by the defined interface law. This can range from simple fresnel law (assuming the material is a simple diopter between internal and surrounding medium) to complex optical surfaces.

This material model is one of the most complex handled by Ocean. Simulations can take a significant time to resolve, as they generate a very large number of significantly contributing paths, taking into account roughness, polarization, refraction and dispersion, combined with advanced interface laws such as coatings.

For modelling a non-transparent rough surface, please refer to reflective material type.

Link

Rough transparent material reference

Oren-Nayar

Example of Oren-Nayar materials with various sigma values

Summary

This material type follows the Oren–Nayar reflectance model. It corresponds to rough diffuse materials, with a user-definable roughness parameter. This is a more refined model than lambertian material for describing diffuse surfaces.

Link

Oren-Nayar material reference

Phong

Example of phong material, with:
*uniform green diffuse color
*refractive index of 1.5
*uniform exponent of 3500

Summary

This material type follows the Blinn-Phong reflection model.

It corresponds to densely diffuse materials, with a surface smooth enough to allow specular reflection, such as smooth paints, laquered or varnished surfaces.

This is a more refined model than Lambertian material material for describing diffuse surfaces. As opposed to Oren-Nayar material material, the Blinn-Phong model was derived more empirically than by using a real physical model, and describes more a shading algorithm for real-time graphic than a BRDF. The actual equations used in Ocean were adapted to fit a physical approach.

Link

Phong material reference

Lambertian transmitter

Example of lambertian transmitter material

Summary

This material type diffuses light in transmission. No light is reflected back from the incident ray, it is fully transmitted, and scattered evenly in every direction. This is similar to the lambertian material, except that it is transmitting instead of reflecting.

This material used on its own is unrealistic and very unlikely to be found in nature. However, a blend of this material type with another diffuse material, such as lambertian, oren-nayar or phong will help modelling thin translucent materials, such as sheets of paper, leaves, cloth, and many other, wich diffusely transmit a fraction of incident light.

Link

Lambertian transmitter material reference

Coated-diffuse

Example of a coated-diffuse material corresponding to a 6mm green glass spandrel with a 50% grey backing paint

Summary

This material simulates an absorbing dielectric layer with a diffuse backing paint. It handles exactly multiple reflections within the layer, and may have a custom interface law such as a coating. This material type models accurately and efficiently enameled or painted glass panes, with exact colorimetry.

Link

Coated-diffuse material reference

Carpaint

Example of a metallic blue car paint material

Summary

This material simulates an absorbing and diffusive dielectric layer loaded with shiny particles. It is mainly used for modelling advanced car paints. The particle texture is visible when rendering close-ups or high definition pictures.

Link

Carpaint material reference

Velvet

Example of velvet material

Summary

This material uses an empirical model which fits the back-reflection caused by thin rods normal to the surface, such as velvet.

Link

Velvet material reference

Lobe

Example of a lobe material measured on a nacre paint

Summary

This material allows defining custom and measure-based BRDFs where the spectral reflectance is a function of the angle between the reflected ray and a specular reflection.

Link

Lobe material reference

Black

A black material

Summary

This material has zero reflectance and zero transmittance : it fully absorbs light. It is mainly used for modelling emitters such as black bodies.

Link

Black material reference

Null

Example of null material

Summary

The null materials is a special material. It is perfectly transparent and invisible, and therefore, does not interact with light.

It has three primary uses:

  • For blending with another material using a blend material, resulting in semi-transparency or holes.
  • For volumetric effects with no visible surface (such as smoke), as it may be associated with a bulk medium
  • For hiding objects without re-exporting the geometry

Link

Null material reference

Blend

Example of blend material between a metal and diffuse clay

Summary

This special materials does blends, or linear combinations, of two other materials, following a user-defined blend function varying between 0 and 1. This is often used for mixing materials (for instance, with a constant blend function equal to 0.5), or for defining areas with different materials (with a blend function taking only 0 and 1 values).

Link

Blend material reference

Linked

Summary

This special material is not a material by itself, but a link to another material defined in the scene. It allows referencing the same material multiple times through different material names. It is especially useful with packaged libraries, whose materials cannot be renamed. A material link to the library material can be created instead.

Link

Linked material reference

Double-sided

Summary

This special material allows defining different properties for the two sides of the geometry surface. It uses two other material definitions, one for each side. Only reflectances are considered, this material has zero transmission by construction.

Link

Double-sided material reference



See also

Node types