Thanks Chris; all very useful and just as needed.

David
"Chris Huff" <chr### [at] maccom> wrote in message
news:chrishuff-9D34F4.20182819112000@news.povray.org...
> In article <3a186773@news.povray.org>, "David Vincent-Jones"
> <geo### [at] galaxynetcom> wrote:
>
> > I am using a series of coloured lights as a part of the scene that
> > are not used to illuminate the area around. Rather like street lights
> > during the daylight hours........ I am using the Light_Fading to keep
> > control over the output.
> >
> > However, from any distance the light simply gets lost so I need some
> > sort of a 'halo' effect to juice up the local area.
>
> There are several options:
> The "highlight glow" method: You can put a transparent sphere with a
> highlight around the light, the highlight will make a glow that appears
> to surround the light source.
> sphere {LightPos, MaxGlowSize
>     texture {
>         pigment {color White filter 1}
>         finish {specular 1 roughness 0.025}
>     }
> }
> Adjust the size of the sphere and the roughness value to get the desired
> effect. Phong highlights should work as well, I just prefer to use
> specular. :-)
> One problem: if you have multiple light sources, you will get multiple
> highlights on each sphere. You might be able to get around this, or at
> least reduce it, with fancy bounding, or you may decide it isn't a
> problem...
>
>
> The "media ball" method: You can put a sphere filled with a spherical
> density emitting media around the light source:
> sphere {LightPos, MaxGlowSize
>     texture {pigment {color White filter 1}}
>     hollow
>     interior {
>         media {
>             emission color LightColor
>             density {spherical color_map {[0 rgb 0][1 rgb 1]}}
>         }
>     }
> }
> Emitting media is fairly fast, and this method is very versatile because
> you can do many effects with different color_maps and turbulence.
>
>
> The glow patch: A recent addition to MegaPOV is the glow patch:
> light_source {...
>     glow {size 1 type 0}
> }
> You can simply specify the glows separately, if you don't need actual
> light sources, which can be useful because many lights can really slow
> things down. Using this patch is probably the easiest way, but the glow
> patch is still quite unfinished. It will give results that are a bit
> more accurate than the "highlight glow" or "media ball" methods
>
>
> And most accurate but slowest, you can fill your scene with scattering
> media, the best way is usually to put the media in a box or other
> container surrounding your scene.
>
> Parameters for media will depend on your scene and what version of POV
> you are using. You may want to get MegaPOV for it's glow patch or the
> new media sampling methods, which can let you get much smoother and
> faster results from media.
>
> --
> Christopher James Huff
> Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
> TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
>
> <><

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