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The fresnel blend layer mode performs a weighted addition of the two materials, with the base material being weighted by the top materials transmission. This ensures that energy is conserved. This is the simplest layer mode and is very commonly used in material models. It matches the behaviour of the MaterialX layer node. |
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Rough gold base layer and dielectric top layer with varying IOR (1.0-3.0) |
Rough Coating
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The simplicity of the fresnel blend mode means that a number of physical effects are ignored. From a physical viewpoint, this layer mode ignores the top layer for the incoming ray, and ignores refraction of the outgoing ray. The IOR of the top layer is also ignored by the base layer, meaning that the relative IOR is incorrect unless it has been manually set. The rough coating layer mode extends this simple model by approximating the physical effects that it ignores. |
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Rough gold base layer and dielectric top layer with varying IOR (1.0-3.0) |
Attenuation
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LamaDielectric (absorptionColor set to red) layered on top of a white LamaDiffuse, layer thickness varying from 1 to 3.2 |
The top layer is considered for both the outgoing and incoming rays, meaning that the ray is attenuated by the top layer twice: once when it leaves and once when it exits. This is the case for both fresnel attenuation at the interface, and for absorption through the thickness of the layer.
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These images show a collection of simple and common material configurations, inspired by Weidlich and Wilkie's arbitrarily layered micro-facet surfaces . These have been rendered with both the fresnel blend mode, and rough coating mode.
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Smooth gold with a rough/bumpy purple coating
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fresnel blend | rough coating |
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Rough/bumpy gold with a smooth purple coating
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