a while back in p.b.i there were some images of "lasers" using photons
and media... how did you guys produce the light source which does not
have a cone of reflected light associated with it??? I can't seem to get
one to look good. Any special tricks?

-thanks 

-paul
-- 



--------------------------------------------------}
Paul Daniel Jones
The Pennslyvania State University

pdj### [at] psuedu
http://research.chem.psu.edu/glassgrp/paul

       C            The way is near, but men
     // \           seek it afar. It is in the
    N    N          easy things, but men seek it
    |    ||         in the difficult things.
    C    C          -Menicius
     \\  /
       C
--------------------------------------------------}

Post a reply to this message

In article <391A0F33.9C7F229E@psu.edu>, Paul Jones <pdj### [at] psuedu> 
wrote:

> a while back in p.b.i there were some images of "lasers" using photons
> and media... how did you guys produce the light source which does not
> have a cone of reflected light associated with it??? I can't seem to get
> one to look good. Any special tricks?

I think you are looking for a cylinderical light source. As I remember, 
in MegaPOV, the light "beams" from a cylinderical light source are 
parallel, unlike in the official version, where they all come from a 
single point(they are just constrained to a cylinder). Don't forget that 
photons don't work properly with cylinder lights(this might be fixed in 
0.5, though).

You could also use a point source with parallel enabled, and use a 
shadow object or projected_through to confine it to a specific beam 
shape.

For getting the light to interact with the media, my advice is to check 
the photon mapping docs and work from code in the demo files at first.

-- 
Christopher James Huff - Personal e-mail: chr### [at] yahoocom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://chrishuff.dhs.org/
TAG Web page: http://tag.povray.org/

Post a reply to this message

"Paul Jones" <pdj### [at] psuedu> wrote in message
news:391A0F33.9C7F229E@psu.edu...
>
> a while back in p.b.i there were some images of
> "lasers" using photons and media... how did you
> guys produce the light source which does not
> have a cone of reflected light associated with
> it??? I can't seem to get one to look good. Any
> special tricks?

Here's a scene I made recently.
http://www.datasync.com/~ericfree/graphics/dls/reflector.jpg

The "laser" was made with a regular point light placed 999900 units along
the X axis and lined up with the center of the laser gun barrel on the Y and
Z.  Just to the right of the laser is a large box with a hole in it to block
all light except that which goes thru the laser gun.

Here's a few code snippets to get you going:

[the mirror surface]
$MirrorMat = material {
  texture {
    pigment {White}
    finish {
      ambient 0
      diffuse 0
      reflection 1
      brilliance 6
      metallic
      reflect_metallic
    }
  }
}

[the box containing the media.  Note that the box stretches right to enclose
the laser light source, is slightly wider than the barrel of the laser gun
(HoleRad*2), and does not touch the wall, floor or ceiling]
$LaserLiteColor = Maroon*15.3;
$   MediaFactor = 0.00125;
box {
  <-RoomX1+0.001,-RoomY+0.001,-HoleRad*2>,
  <999990,RoomY-0.001,HoleRad*2>
  pigment {rgbf 1.0}
  hollow
  interior {
    ior 1
    media {
      intervals 3
      samples 1, 1
      confidence 0.995
      variance 1/256
      scattering {
        1,
        LaserLiteColor*MediaFactor
        extinction 0
      }
    }
  }
}

[the laser light]
light_source {
  <999900,0,0>, LaserLiteColor
  media_attenuation on
  photons {
    refraction off
    reflection on
  }
}

If you need more than this, the entire source code for the scene is in the
MegaPOV 0.5 demo files in the "photons" directory.  Look for "reflector.pov"

> -thanks

Yer welcome.

Eric
--------------------
http://www.datasync.com/~ericfree
--------------------
"I don't like it, and I'm sorry I ever had anything to do with it."
- Erwin Schrodinger talking about Quantum Mechanics.

Post a reply to this message

> The "laser" was made with a regular point light placed 999900 units along
> the X axis and lined up with the center of the laser gun barrel on the Y and
> Z.  Just to the right of the laser is a large box with a hole in it to block
> all light except that which goes thru the laser gun.

What about the cylindrical light?  Isn't that some kind of laser?

Simon

Post a reply to this message

Simon Lemieux wrote:
> 
> What about the cylindrical light?  Isn't that some kind of laser?

Yes, the cylindrical light_source should be ideally suited for lasers.
In MegaPOV (unlike in official POV) it has parallel rays, raytracing equivalent
of the coherent light of an actual laser.
I seem to remember that there used to be a problem with cylindrical light
sources and photons, but this has probably been fixed by now.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg

Post a reply to this message