I apologize if this type of question has been asked before,
but is there such a thing as a non point light source?

I was looking to do like a light house type of beam
of light (I'm using the media features and a spotlight),
but it looks strange with the light only coming from
one point.

Is there anyway to have a an object emit light?
Kind of like a flashlight (where it appears as if
the end of a cylinder is emitting light?

Should I try adding in some mirror objects (kind
of like a real flashlight) and use a regular (non-spot)
light source, or should I use multiple spotlights,
or something else?

Thanks for any help.

-JamesF.
--
==============================================================
James Fitzgerald             Argon Engineering Associates Inc.
Jam### [at] argonengcom          (703) 591-3614 x103
==============================================================

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James Fitzgerald <jam### [at] argonengcom> wrote in message
362FB99E.AC215E59@argoneng.com...
>I apologize if this type of question has been asked before,
>but is there such a thing as a non point light source?
>
>I was looking to do like a light house type of beam
>of light (I'm using the media features and a spotlight),
>but it looks strange with the light only coming from
>one point.

Maybe you should try and use area_light with spotlight parameters specified.
Slower, though.

>Is there anyway to have a an object emit light?
>Kind of like a flashlight (where it appears as if
>the end of a cylinder is emitting light?

No. But you can play around (not in this case) with radiosity and really
high ambient values.

>Should I try adding in some mirror objects (kind
>of like a real flashlight) and use a regular (non-spot)
>light source, or should I use multiple spotlights,
>or something else?

That would require that POV models specular reflections, and it does nor.
Multiple spotlights placed in a circle *might* work, but I think that, if
you only want to see the beam and not any shadows in it, you can use a very
distant cylindrical light that points at the lighthouse.

>Thanks for any help

>-JamesF.
>--
>==============================================================
>James Fitzgerald             Argon Engineering Associates Inc.
>Jam### [at] argonengcom          (703) 591-3614 x103
>==============================================================

Peter

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As far as I can tell, your only option is to use an array of spotlights (placed
in a circular pattern and quite close together). Using an area_light source
doesn't help, since POV's area lights only affect the shadows - the light beam
looks exactly the same as with a single light source.

Having said that, I think that with media effects finalized/finalised ;) in 3.1,
POV really needs true area lights, i.e. lights which truly have dimensions. The
current system just doesn't work with media (although it's faster)

Margus

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Margus Ramst <mar### [at] peakeduee> wrote in message
363### [at] peakeduee...
>As far as I can tell, your only option is to use an array of spotlights
(placed
>in a circular pattern and quite close together). Using an area_light source
>doesn't help, since POV's area lights only affect the shadows - the light
beam
>looks exactly the same as with a single light source.

So you are saying that an area light is identical to a point light for
scattering media tests? I know this is the case with area lights and light
falloff, but this media thingy is news to me. I just never had the guts to
try media *and* area_light in the same scene. Any other cases I don't know
about?

<snip>

>Margus

Peter

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light_source {} with cylinder type light sounds like a possibility alright.
Vary the tightness, falloff, and radius as needed.
I haven't tried it yet, but if the idea is to create an actual "area" of light 
at the source then this might be the solution.

Message <362ff07d.0@news.povray.org>, Peter Popov  typed...
>Multiple spotlights placed in a circle *might* work, but I think that, if
>you only want to see the beam and not any shadows in it, you can use a very
>distant cylindrical light that points at the lighthouse.

I take it this means orient the cylinder light along the light beam axis. 
"distant"?, I don't understand that, because it has no distance along the axis 
unless fade_distance and fade_power is used, so putting it at the beam origin 
and with point_at away from there (what else?) then the light distance will 
fade as it should.

>
>Peter
>

-- 
 omniVERSE: beyond the universe
  http://members.aol.com/inversez/POVring.html
=Bob

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Try using an area light and looks_like - details in the docs
Mike

Margus Ramst wrote in message <363### [at] peakeduee>...
>As far as I can tell, your only option is to use an array of spotlights
(placed
>in a circular pattern and quite close together). Using an area_light source
>doesn't help, since POV's area lights only affect the shadows - the light
beam
>looks exactly the same as with a single light source.
>
>Having said that, I think that with media effects finalized/finalised ;) in
3.1,
>POV really needs true area lights, i.e. lights which truly have dimensions.
The
>current system just doesn't work with media (although it's faster)
>
>Margus

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Peter Popov wrote:
> So you are saying that an area light is identical to a point light for
> scattering media tests? I know this is the case with area lights and light
> falloff, but this media thingy is news to me. I just never had the guts to
> try media *and* area_light in the same scene. Any other cases I don't know
> about?
> 
> Peter

Well, yes and no. An area light _does_ cast soft shadows into the media (look at
the scene I've included, comment out area_light to see the difference). This is
very nice; but an area light's rays still start from one point in space (look at
the tip of the spotlight cone in my scene). I haven't tried out
media_attenuation and area_lights yet, but I guess the same problem persists.

Margus

//Start scene//

#include "colors.inc"
camera {orthographic
        location <0,4,-8>
        up y*15*.75
        right x*15
        look_at y*4}

light_source {0, 5
              spotlight radius 20 falloff 20 point_at y
              area_light x,z,3,3 adaptive 1 jitter
              }

media {scattering {1, .1}}

cylinder {<0,4,-7>,<0,4,7>,.75 pigment {Red}}

polygon {4,<-.5,0,-.5>,<-.5,0,.5>,<.5,0,.5>,<.5,0,-.5>
	pigment {White} finish {ambient 1 diffuse 0} no_shadow}

plane {y, 8 pigment {White} hollow}

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It took *me* some time to understand what I had said two weeks ago :)

A cyllindrical light source is actually a spotlight but the spreading of
light is limited by a cylinder and not a cone. Putting one of these inside
the lighthouse would do you no good in comparison with point-, spot- or area
lights. However, if the beam does not illuminate any object, i.e. no shadow
is cast onto the atmosphere/media inside the ray, then one could place a
cylindrical light source on a large distance from the lighthouse and point
it *to* the latter and no one will notice the trick (if there's a bird in
the beam it will be obvious that the shadow is cast in the opposite
direction). The farther the light is, the better, since light rays will look
more and more parallel with the increase of distance, and that's the purpose
of a real-life parabollic mirror in a light house or a floodlight, after
which effect Mr. Fitzgerald is.

I hope I put it down more clearly this time.

Peter

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