Specular Map question.

    Hi guys. I have a question. About specular maps.


    So, materials are meant to simulate real world lighting effects, right?


    From what I have read, in nature, specular reflections happens when the incident rays hits a flat and polished surface and generates another ray with the same angle taking as reference the surface normal.


    [Blocked Image: http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture10/images/set_1.gif]


    That's the practical results:


    [Blocked Image: http://academic.emporia.edu/aberjame/student/kuss2/15.jpg]


    I understant the point of normals maps, they change the normals to fake geometry, but the use of specular maps is giving me some doubts:


    • A rough concrete wall is not flat and polished, so why artists create specular maps for them since specular reflections doesn't happen in such surfaces?
    • Also, the real specular reflections are like the picture above, I mean, the surface "mirror" the image comprised of the incident rays, in games that reflection is just a "white blur image". This is to reduce the computing calculations?
    • Also, using normals maps AND specular maps sounds awkward, since a normal map "creates" a rough surface, and in a surface like this there are no specularity.


    Thanks, and merry christimas.

    Specular maps are an approximation for how much light a surface reflects back. Before the adoption of physically-based rendering in the newer engines (google for it), this value could be anything really, which in turn lead to a lot of consistency problems, since in real life no surface can reflect more energy than it receives, but in a game you can crank up your specular highlights to any value you want. Reflections were done separately either by linking your material to a cubemap or using real time reflections (for water and shit like that).


    I never worked with a PBR engine, but from my understanding the actual reflection is derived from the specular intensity and roughness (glossiness) terms. In pratical terms this means that the highest the specular and roughness, the stronger and sharper the reflections and highlights are, while a low roughness value creates a fainter larger specular highlight and blurry reflections:


    [Blocked Image: http://www.fxguide.com/wp-content/uploads/2013/05/EnergyConservation.png]


    [Blocked Image: http://i.imgur.com/yofMClu.jpg]


    You can try the new Marmoset toolbag to check out how PBR works, but at the end of the day keep in mind that these are just approximations, we are making games not science

    The idea with PBR is that you define glossiness defines the roughness of the surface, similar to the Normalmap - just instead of giving an actual Vector back, it just defines the bluriness/distribution of the highlight evenly, faking what would happen if you had a very high detail normalmap with nice filtering.


    The specular defines the color of that highlight mostly, but used to be the control mechanism for the brightness of the reflection as well. In PBR the idea is that you've got 'metally' surfaces and 'organic' surfaces, where metal is mostly specular, and little diffuse (basically just a tinted reflection), while organics are mostly diffuse and little specularity.

    What specular map isn't is real realtime reflections. That is, the specular doesn't create a mirror by itself. In real world every surface reflects off light and absorbs some light, there is no surface that is a perfect, 100% specular, mirror or 0%, perfect black, surface.

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