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### Density

Particles of media are normally distributed in constant density throughout the media. However the `density` statement allows you to vary the density across space using any of POV-Ray's pattern functions such as those used in textures. If no `density` statement is given then the density remains a constant value of 1.0 throughout the media. More than one `density` may be specified per `media` statement. See "Multiple Density vs. Multiple Media".

The syntax for `density` is:

DENSITY:
`
  density {
` [DENSITY_IDENTIFIER] [DENSITY_TYPE] [DENSITY_MODIFIER...] `}`
DENSITY_TYPE:
  PATTERN_TYPE
| COLOR
DENSITY_MODIFIER:
  PATTERN_MODIFIER
| DENSITY_LIST | `
  color_map{
` COLOR_MAP_BODY `}` | `colour_map{` COLOR_MAP_BODY `}` | `
  density_map{
` DENSITY_MAP_BODY `}`

The `density` statement may begin with an optional density identifier. All subsequent values modify the defaults or the values in the identifier. The next item is a pattern type. This is any one of POV-Ray's pattern functions such as `bozo`, `wood`, `gradient`, `waves`, etc. Of particular usefulness are the `spherical`, `planar`, `cylindrical`, and `boxed` patterns which were previously available only for use with our discontinued `halo` feature. All patterns return a value from 0.0 to 1.0. This value is interpreted as the density of the media at that particular point. See "Patterns" for details on particular pattern types. Although a solid COLOR pattern is legal, in general it is used only when the `density` statement is inside a `density_map`.

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