Specular#
The specular component controls direct surface reflections in materials. It simulates mirror-like behavior by defining reflection intensity, surface micro-roughness, and angle-dependent reflectivity (Fresnel effect).
Parameters
Display Name |
Name |
Type |
Default |
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specular_reflection_weight |
float |
1.0 |
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specular_reflection_color |
color |
1.0, 1.0, 1.0 |
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specular_reflection_roughness |
float |
0.2 |
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specular_reflection_ior_preset |
enum |
ior_custom |
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specular_reflection_ior |
float |
1.5 |
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specular_reflection_anisotropy |
float |
0.0 |
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specular_reflection_anisotropy_rotation |
float |
0.0 |
This layer models a GGX microfacet dielectric BRDF under the coating layer. Due to Fresnel, this layer is not energy conversing. Thus the energy that is not reflected is transmitted to the underlying layers.
Weight
This parameter sets the amount of the specular reflection. Lowering this value increases light transmission through the object’s volume.
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When Metalness is greater than 0.0, this parameter sets the edge tint weight for the metal surface.
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Color
This parameter sets the color of the specular reflection. While some metallic (conductor) surfaces have colored specular reflections, dielectric surfaces have only achromatic specular reflections.
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Tip
Setting the specular reflection color for dielectric surfaces other than white is not physically correct.
When metalness is greater than 0.0, this parameter sets the edge tint color.
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Roughness
This parameter sets the surface microfacet’s irregularities that cause light diffusion. At 0.0 simulates a perfect and smooth reflective surface, while increasing the value causes reflective highlights to diverge or appear blurred.
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Roughness affects both specular reflection and specular transmission.
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Tip
Roughness can create effects like torn surfaces, galvanized metal, or surfaces with fingerprints and smudges.
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IOR Preset
This parameter presents a list of known IORs (index of refractions) for various materials, including glass, ice, diamond, skin. One can use custom IOR by setting this parameter to ior_custom and a value for the specular reflection’s IOR parameter.
IOR
This parameter sets IOR (index of refraction), which affects surface Fresnel reflectivity. The IOR defines the ratio between reflection on the surface front, facing the viewer, and the surface edges, facing away the viewer.
At values above 1.0, the reflection appears stronger on the surface edges and weaker on the surface front. At values less than 1.0, the Fresnel is disabled, and the specular reflection appears as a uniform highlight over the surface.
Tip
At high values, the surface will look similar to a metallic surface. If a metallic look is desired, the metalness parameter is encouraged instead since the range [0, 1] can be easily mapped with an input texture.
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IOR affects both the specular reflection and the specular transmission.
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Anisotropy
This parameter sets the specular reflection anisotropy. Reflectance changes based on the surface orientation are called anisotropic. If the reflectance is uniform in all directions and does not change based on the surface’s rotation or orientation, it is isotropic.
At values above 0.0, the surface transmits and reflects incoming light with a directional bias. Thus it appears rougher in a specific direction.
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Rotation (radians)
This parameter sets the orientation of the anisotropic effect in radians. At 1.0, the anisotropic effect is rotated by 180 degrees. For brushed metallic surfaces, the anisotropic effect should stretch out in a direction perpendicular to the brushing direction.
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