I would like to create a sector light, such as would be found on a small
boat.
It is rather like a pie chart with one part showing a red light, one part
green and one part remains black.
It is important that as the angle changes there is no black area between the
red and green nor any bleed from one color to the other.
2 spotlights with a very sharp fall-off looks about correct but how can I
fit two of them ( or more ) into a single cylinder?

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In article <384ee843@news.povray.org>, "David Vincent-Jones" 
<geo### [at] galaxynetcom> wrote:

> I would like to create a sector light, such as would be found on a small
> boat.
> It is rather like a pie chart with one part showing a red light, one part
> green and one part remains black.
> It is important that as the angle changes there is no black area between 
> the
> red and green nor any bleed from one color to the other.
> 2 spotlights with a very sharp fall-off looks about correct but how can I
> fit two of them ( or more ) into a single cylinder?

If I understand what you want, try using a sphere with a radial pattern, 
and a color map divided into a red section, a green section, and a black 
section. Give the red and green a filter of 1, place a spotlight inside 
the sphere, oriented correctly, and use the reorient macro or just 
transforms to move it into position.
Oh, it helps to know that you can add light_sources to a union, that 
makes keeping everything together much easier.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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David Vincent-Jones <geo### [at] galaxynetcom> wrote:
> I would like to create a sector light, such as would be found on a small
> boat.
> It is rather like a pie chart with one part showing a red light, one part
> green and one part remains black.
> It is important that as the angle changes there is no black area between
the
> red and green nor any bleed from one color to the other.
> 2 spotlights with a very sharp fall-off looks about correct but how can I
> fit two of them ( or more ) into a single cylinder?

How about recreating the light just as it would be in real life, ie. put a
white light source behind a coloured filter with the pattern you desire, eg:

camera {location <1, 1, -3> look_at <0, 0, 10>}
light_source {<-100, 200, -400> rgb .5}  // Filler light
plane {z, 10 pigment {checker rgb .5, rgb 1}}

union {
   light_source {0, rgb 1
      spotlight point_at z radius 30 falloff 45}
   disc {z*.1, z, 1 hollow
      pigment {radial color_map {
         [.3 rgb 0] [.3 rgbf <1, 0, 0, 1>]
         [.7 rgbf <1, 0, 0, 1>]  [.7 rgbf <0, 1, 0, 1>]}
         rotate x*90}}
   scale .001} // Scale very small so filtering disc isn't visible

You can use all sorts of filtered pigments (including image maps and
animated pigments) to create projections of just about anything you want...

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> I would like to create a sector light, such as would be found on a small
> boat.
> It is rather like a pie chart with one part showing a red light, one part
> green and one part remains black.

	Another real life approach is to put a physical partition
between two lights.

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