How can i create a realistic laser line?
So far I just managed to create it by passing red light through a thin
gap...the result is not really sufficient.

Regards

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"zorni" <zor### [at] gmxat> wrote in message
news:3f165a0c$1@news.povray.org...
> How can i create a realistic laser line?
> So far I just managed to create it by passing red light through a thin
> gap...the result is not really sufficient.
>
> Regards

    I believe that the common solution is to use a cylinder full of emitting
medium.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

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Sir Charles W. Shults III wrote:
>"zorni" <zor### [at] gmxat> wrote in message
>news:3f165a0c$1[at]news.povray.org...
>> How can i create a realistic laser line?
>> So far I just managed to create it by passing red light through a thin
>> gap...the result is not really sufficient.
>>
>> Regards
>
>    I believe that the common solution is to use a cylinder full of emitting
>medium.
>
>Cheers!
>
>Chip Shults
>My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
>
Or if you want to model it close to the way it works, a cylinder light
passing
through a scattering medium should work (but it would also likely be
slower...)

I'd use emitting media for 'laser guns' and cylinder-lights through
scattering
media for 'scientific' lasers, probably (and especially if I wanted to
bounce
them off of mirrors).

--Chris

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In article <3f165a0c$1@news.povray.org>, "zorni" <zor### [at] gmxat> 
wrote:

> How can i create a realistic laser line?

What exactly do you mean by "laser line"? A laser beam that is spread 
out to make a long line on a surface, as is used in some laser levels? 
The visible line of scattered light a laser makes when travelling 
through a scattering medium? The radial lines you some times get when 
you take a picture with the laser going into the camera?


> So far I just managed to create it by passing red light through a thin
> gap...the result is not really sufficient.

In what way is this not enough? It's difficult to give a better solution 
when you don't say why the old solution isn't good enough.

Assuming you want a laser beam through a scattering medium: the simplest 
and most accurate way is with photons deposited in scattering media. The 
optics.pov demo scene gives a good example of this. For a laser, it 
would be better to use a parallel cylinder light instead of the 
halogen-like spotlight in that scene, but the technique is the same.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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In article <3f165a0c$1@news.povray.org> , "zorni" <zor### [at] gmxat> 
wrote:

> How can i create a realistic laser line?
> So far I just managed to create it by passing red light through a thin
> gap...the result is not really sufficient.

I suppose you want it to be visible?  Take a look at optics.pov that comes
with POV-Ray 3.5.

    Thorsten

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Christopher James Huff wrote:
>In article <3f165a0c$1[at]news.povray.org>, "zorni" <zor### [at] gmxat>
>wrote:
>
>> How can i create a realistic laser line?
>
>What exactly do you mean by "laser line"? A laser beam that is spread
>out to make a long line on a surface, as is used in some laser levels?
That's the problem I am interested in.
What would solve my problem: if there was an option similar to
"cylinder", but constraining the light to the space between two
parallel planes.

>In what way is this not enough? It's difficult to give a better solution
>when you don't say why the old solution isn't good enough.
When sending light through a small gap the width of the projected
line depends on the distance to the light-source/gap.

thanks,

Wolfgang

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In article <web.3fa0f1b69a8fede7e9df71c0@news.povray.org>,
 "stoecher" <sto### [at] gmxat> wrote:

> >In what way is this not enough? It's difficult to give a better solution
> >when you don't say why the old solution isn't good enough.
> When sending light through a small gap the width of the projected
> line depends on the distance to the light-source/gap.

Hmm...use an ordinary point light, and a negative light at the same 
position using projected_through with a union of two planes. The 
negative light will only illuminate parts of the scene on the other 
sides of the planes, cancelling out the actual light on all parts of the 
scene "inside" the union of planes.

light_source {Point, Color}

light_source {Point, -Color
    projected_through {
        union {plane {y,-0.1} plane {-y,-0.1}}
    }
}

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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Christopher James Huff wrote:
>light_source {Point, Color}
>light_source {Point, -Color
>    projected_through {
>        union {plane {y,-0.1} plane {-y,-0.1}}
>    }
>}

great idea!
But there is a problem with shadows,
as can be seen in the scene below.
Is this a bug in povray?

thank you,

Wolfgang
--------------------------------------
#include "colors.inc"
camera {location <0,20,20> look_at <0,0,0>}
light_source {<-14,20,30> White}

#declare LaserPoint = <0,0,20>;
light_source {LaserPoint, Red}
light_source {LaserPoint, -Red
    projected_through {
        union {plane {y,-0.3} plane {y,0.3}}
    }
}

cylinder
{ <0,-3,0>, <0,3,0>, 8 open
  pigment {Yellow}
}
triangle
{ <12,-3,0> <16,-3,0> <14,3,0>
  pigment {Yellow}
}
// background plane showing green shadows!
plane {z,-10 pigment{White}}

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In article <web.3fbfd9e59a8fede7cf187cb30@news.povray.org>,
 "stoecher" <sto### [at] gmxat> wrote:

> But there is a problem with shadows,
> as can be seen in the scene below.
> Is this a bug in povray?

Not a bug. Objects do not shadow light from a projected_through light 
until it hits the projected_through object. The light still comes from a 
single point, so while the positive light is getting shadowed, the 
negative light is constantly leaking through the projected_through 
planes past the shadowing object. Parallel lights will partially fix 
this problem:

light_source {LaserPoint, Red
    parallel point_at -z
}
light_source {LaserPoint, -Red
    parallel point_at -z
    projected_through {
        plane {z, 20 clipped_by {union {plane {-y,-0.3} plane {y,-0.3}}}}
    }
}

However, they introduce a new one...all light rays are parallel, rather 
than originating from a vertical line. This will affect shading and 
shadowing, but may not be noticeable. You could approximate a "spread" 
light by using multiple spot lights combined with this technique...

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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