The Shape Machine
Highlight
From the PovRay docs:
7.6.3.3 Highlights
Highlights are the bright spots that appear when a light source reflects off of a smooth object. They are a blend of specular reflection and diffuse reflection. They are specular-like because they depend upon viewing angle and illumination angle. However they are diffuse-like because some scattering occurs. In order to exactly model a highlight you would have to calculate specular reflection off of thousands of microscopic bumps called micro facets. The more that micro facets are facing the viewer the shinier the object appears and the tighter the highlights become. POV-Ray uses two different models to simulate highlights without calculating micro facets. They are the specular and Phong models.
Note that specular and Phong highlights are not mutually exclusive. It is possible to specify both and they will both take effect. Normally, however, you will only specify one or the other.
Phong Amount and Phong Size
| Phong Amount (Size = 2) | |||||
|---|---|---|---|---|---|
| 0.0 | 0.2 | 0.4 default | 0.6 | 0.8 | 1.0 |
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| Phong Size (Amount = 0.4) | |||||
|---|---|---|---|---|---|
| 0.5 | 1.0 | 1.5 | 2.0 default | 2.5 | 3.0 |
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From the PovRay docs:
7.6.3.3.1 Phong Highlights
The phong keyword controls the amount of Phong highlighting on the object. It causes bright shiny spots on the object that are the color of the light source being reflected.
The Phong method measures the average of the facets facing in the mirror direction from the light sources to the viewer.
Phong's value is typically from 0.0 to 1.0, where 1.0 causes complete saturation to the light source's color at the brightest area (center) of the highlight. The default phong 0.0 gives no highlight.
The size of the highlight spot is defined by the phong_size value. The larger the phong size the tighter, or smaller, the highlight and the shinier the appearance. The smaller the phong size the looser, or larger, the highlight and the less glossy the appearance.
Typical values range from 1.0 (very dull) to 250 (highly polished) though any values may be used. Default phong size is 40 (plastic) if phong_size is not specified.
Specular
| Roughness = 0.5 | |||||
|---|---|---|---|---|---|
| 0.05 default | 0.1 | 0.2 | 0.4 | 0.7 | 1 |
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Roughness
| Specular = 0.5 | |||||
|---|---|---|---|---|---|
| 0.001 default | 0.01 | 0.1 | 0.4 | 0.7 | 1 |
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7.6.3.3.2 Specular Highlight
A specular highlight is very similar to Phong highlighting but it uses slightly different model. The specular model more closely resembles real specular reflection and provides a more credible spreading of the highlights occurring near the object horizons.
The specular value is typically from 0.0 to 1.0, where 1.0 causes complete saturation to the light source's color at the brightest area (center) of the highlight. The default specular 0.0 gives no highlight.
The size of the spot is defined by the value given for roughness. Typical values range from 1.0 (very rough - large highlight) to 0.0005 (very smooth - small highlight). The default value, if roughness is not specified, is 0.05 (plastic).
It is possible to specify wrong values for roughness that will generate an error when you try to render the file. Don't use 0 and if you get errors check to see if you are using a very, very small roughness value that may be causing the error. For example:
finish {specular 0.9 roughness 0.02}