# Specular map: What about the specular reflection's highlight' size?

I think I know what a specular map is and what it's used for (here is an example).

http://www.rastertek.com/dx10tut21.html

One of the models of specularity that are highly popular is Phong. In Phong there is a parameter sometimes called "shininess" which basically controls the size of the highlight. A large value yields a tiny highlight.

How is that value expressed in the specular map? It appears to me it is common to use the specular map to control the brightness but not the size of the specular highlight in games.

Am I wrong in thinking so? Mind you I'm not adept in game rendering and well aware that the naive implementation of Phong (with ray-tracing) raises the dot product of the vector from the camera source with the reflected vector of the light beam by the power of shininess which appears computationally heavy but still I wonder:

Are specular maps by definition without Phong's shininess value? Is that rarely or never used at all in interactive rendering? Is the value simply set to a small constant?

specularPower = pow(2.0, 13.0 * shininessMap)

Often times this is called a "gloss map", and the value stored in the map is called "gloss". This enables the texture map to have a range from 0 to 1 just like most other textures, so standard authoring tools and formats can be used. But after applying the pow() function, the range of specular powers is 1 to 8192 in the function above (of course, different constants can be used to get a wider or narrower range). So you can get a useful range of specular powers from a standard texture map.