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src/docs/asciidoc/jme3/advanced/pbr_part2.adoc

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 This is a bit more complicated for specular. We need a physically plausible BRDF. We use what is called a *Microfacet BRDF*. So what is it?
 
 It states that at a micro level a surface is not plane, but formed of a multitude of little randomly aligned surfaces, the microfacets. Those surfaces acts as small mirrors that reflects incoming light. The idea behind this BRDF is that only some of those facets may be oriented so that the incoming light reflects to your eye. The smoother the surface, the more all facets are aligned, and the most neat is the light reflection. In the contrary, if a surface is rough, the facets are more randomly oriented so the light reflection is scattered on the surface, and the reflection looks more blurry.
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 image::jme3/advanced/Specular.png[Specular.png,with="320",height="250",align="center"]
 Microfacet specular factor for a direct light source. On the left a smooth surface, on the right a rough one. Note how the reflection is scattered on the surface when it’s rough.