This property allows you to adjust the percentage of color filtering applied to reflected images. At 0%, reflections obey the normal blended or additive reflections. At 100%, reflection colors are fully filtered by the surface color.
Reflection filtering means that the reflected images are filtered by the reflecting object surface color. Some consequence of applying a filter to reflection is that some part of the reflected image may not get reflected at all. For instance trying to reflect a pure blue object off a pure red object will result in no reflection at all. That is because in order to be able to reflect the blue component, an object surface color need to have some blue component in it. The extreme example would be the impossibility to reflect any image off a black object surface because any refelcted image filtered with black will result in black.
The normal handling of reflected images takes into account the reflectivity. That is surface color filter is applied in inverse proportion to the reflectivity. When reflectivity is set to 100%, then no filtering occurs. If reflectivity is set to 70% then a 30% filtering is applied to the reflected image. This is particularly important when considering the Fresnel reflectivity where at full grazing angle, reflectivity becomes 100%. In the real world, when reflectivity is 100%, it is 100% for all wavelength thus no filtring at all should occur. Furthermore, this allows reflection to occur even on very dark or black surfaces.
With reflection filter, it is possible to adjust the amount of filtering that gets applied to reflected images. The range of filtering goes from 0% to 100% but it actually goes from the inverse of reflectivity up to 100%. For instance, on a 70% reflective surface, setting filter to 0% will result in the normal 30% filtering to be applied. A filter of 100% will result in 100% filtering and any values between 0% and 100% will result in filtering between 30% and 100%. Note that reflection filter directly affect the Fresnel term. At 100% filtering, the Fresnel term is completely cancelled out.
The color used for filtering reflection comes from the specular color chip unless the speculkar color chip is the same color as the diffuse color chip. In which case, the reflection color comes from the resolved surface diffuse color which may depend on color decals or materials.
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Reflection filtering have the most impact when reflectivity is
high.
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Reflectivity of around 75% allows a nice range of reflection
filtering.
Comparing with real gold photographs, a good seting for gold would be with
around 75% reflectivity and a reflection filtering of a little less than 50%.
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Reflection filtering effect becomes almost unnoticeable with reflectivity below 50% (project file by John Keates)
