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#### Using Surface Highlights

In the glass example above, we noticed that there were bright little hotspots on the surface. This gave the sphere a hard, shiny appearance. POV-Ray gives us two ways to specify surface specular highlights. The first is called Phong highlighting. Usually, Phong highlights are described using two keywords: `phong` and `phong_size`. The float that follows `phong` determines the brightness of the highlight while the float following `phong_size` determines its size. Let's try this.

      sphere { <0,0,0>, 1

        pigment { Gray50 }

        finish {

          ambient .2

          diffuse .6

          phong .75

          phong_size 25

        }

      }

Rendering this we see a fairly broad, soft highlight that gives the sphere a kind of plastic appearance. Now let's change `phong_size` to 150. This makes a much smaller highlight which gives the sphere the appearance of being much harder and shinier.

There is another kind of highlight that is calculated by a different means called specular highlighting. It is specified using the keyword `specular` and operates in conjunction with another keyword called `roughness`. These two keywords work together in much the same way as `phong` and `phong_size` to create highlights that alter the apparent shininess of the surface. Let's try using specular in our sphere.

      sphere { <0,0,0>, 1

         pigment { Gray50 }

         finish {

            ambient .2

            diffuse .6

            specular .75

            roughness .1

        }

      }

Looking at the result we see a broad, soft highlight similar to what we had when we used `phong_size` of 25. Change `roughness` to .001 and render again. Now we see a small, tight highlight similar to what we had when we used `phong_size` of 150. Generally speaking, specular is slightly more accurate and therefore slightly more realistic than phong but you should try both methods when designing a texture. There are even times when both phong and specular may be used on a finish.

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