POV-Ray : Newsgroups : povray.general : ray of light line laser with projector Server Time: 25 Apr 2014 04:14:00 GMT
  ray of light line laser with projector (Message 1 to 7 of 7)  
From: CRIS
Subject: ray of light line laser with projector
Date: 6 Feb 2012 19:25:01
Message: <web.4f30284f95c8b71f60feafb60@news.povray.org>
Hi guys. I have to simulate a rays of light of a line laser.
(http://laserlineoptics.com/powell_primer.html) I do this with a Projector (a
small prism) and a standard light source. I dont' understand why if i use a
spotlight doesn't work , that is the line that is projected on the box is short
but if i use a standard light source the line that is projected seems to be
correct. Another question : why don't if i multiply a color of 'red principal
light' by a constant i see also the ray of light that hits internal diagonal
bars? the code is this:

//-----------------------------------------------

#include "colors.inc"
#include "textures.inc"
#include "shapes.inc"
#include "metals.inc"
#include "glass.inc"
#include "woods.inc"
#include "stones.inc"



// camera normale
camera {
location <00.0, 20.0,-40.0>
look_at <0.0, 10.0, 0.0>
blur_samples 50

       }

// camera 2
/*camera {
location <10.0, 20.0,30.0>
look_at <-10.0, 10.0, 0.0>
blur_samples 50

       }   */



 declare a= 1;
 declare b=0.54;
 declare Projector = prism   {
          linear_spline
          3, 3.002, 4,
          <0,0>, <-a,b>,<a,b>, <0,0> //outer rim
           texture{ pigment{ color Red } }


        }


 // principal light
 light_source{ <0,3.001,-0.1>
 //light_source{ <0,3.001,-0.9>
        color Red     // if i multiply *100 i see light on internal bar
        /*spotlight
        radius 10
        falloff 20
        tightness 20
        point_at <0, 3.015, 2>  */


        projected_through { Projector }

 } //end of light_source

 Projector

  // box test  laser line
 box {

        <-125, 0, 90>, // angolo inferiore sinistro (più vicino)
        < 125, 10, 95>
        texture { DMFLightOak }
 translate z*-45

        }



#declare bars =

union {

        box {
        <0, 0, 0>, // angolo inferiore sinistro (più vicino)
        < 3, 4, 70> // angolo superiore destro (più lontano)
        texture {
                T_Stone25 // predefinita da stones.inc
                //pigment {Green}
                //scale 10 //
                }


             }

        box {
        <0, 0, 0>, // angolo inferiore sinistro (più vicino)
        < 70, 4, 3> // angolo superiore destro (più lontano)
        texture {
                T_Stone25 // predefinita da stones.inc
                //pigment {Green}
                //scale 10 //
                }

             }

        rotate y*-45
        translate x*-0.2
        translate z*-6



      }

bars

//another light

light_source { <5, 30, -30> color White }
//------------------------------------------------


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From: Christian Froeschlin
Subject: Re: ray of light line laser with projector
Date: 6 Feb 2012 22:46:15
Message: <4f305837$1@news.povray.org>
CRIS wrote:

> small prism) and a standard light source. I dont' understand why if i use a
> spotlight doesn't work , that is the line that is projected on the box is short

The effect of a spotlight is to produce a cone of light, reducing this
to 20 degrees as you also yields a shorter line. Using

   radius 45
   falloff 0
   tightness 0

you get the full line back.

> Another question : why don't if i multiply a color of 'red principal
> light' by a constant i see also the ray of light that hits internal diagonal
> bars? 

the line

   Projector

renders the projection object itself and you see that part that
is not embedded in your bars only.


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From: CRIS
Subject: Re: ray of light line laser with projector
Date: 8 Feb 2012 11:25:01
Message: <web.4f325ae88af170f5a2ae615c0@news.povray.org>
Christian Froeschlin <chrfr [at] chrfrde> wrote:
> CRIS wrote:
>
> > small prism) and a standard light source. I dont' understand why if i use a
> > spotlight doesn't work , that is the line that is projected on the box is short
>
> The effect of a spotlight is to produce a cone of light, reducing this
> to 20 degrees as you also yields a shorter line. Using
>
>    radius 45
>    falloff 0
>    tightness 0
>
> you get the full line back.
>
> > Another question : why don't if i multiply a color of 'red principal
> > light' by a constant i see also the ray of light that hits internal diagonal
> > bars?
>
> the line
>
>    Projector
>
> renders the projection object itself and you see that part that
> is not embedded in your bars only.

Oh thanks! I tried and it works!I had never tried to put falloff on '0'.  I
noted that if i put the value of radius > 45 the length of line does not change.
I think now depend on the value  of the base of prism (projector) but is
correct.

Rather about my second question, maybe I explained bad, if i put in the
spotlight source : 'color Red * 1' i don't see the light on the internal bars
but if i put (for example) 'color Red * 200'  i see the red line on the internal
bars. Maybe it depends on the power of light?


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From: Christian Froeschlin
Subject: Re: ray of light line laser with projector
Date: 8 Feb 2012 22:40:17
Message: <4f32f9d1$1@news.povray.org>
CRIS wrote:

> Rather about my second question, maybe I explained bad, if i put in the
> spotlight source : 'color Red * 1' i don't see the light on the internal bars
> but if i put (for example) 'color Red * 200'  i see the red line on the internal
> bars.

your light source, bars and projection object all end on x = 0,
this coincidence is likely to get you into numerical issues. Also,
at a grazing angle diffuse illumination is close to 0 but becomes
visible if you boost the light power by 200.


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From: CRIS
Subject: Re: ray of light line laser with projector
Date: 15 Feb 2012 14:20:01
Message: <web.4f3bbe678af170f52dd853be0@news.povray.org>
Christian Froeschlin <chrfr [at] chrfrde> wrote:
> CRIS wrote:
>
> > Rather about my second question, maybe I explained bad, if i put in the
> > spotlight source : 'color Red * 1' i don't see the light on the internal bars
> > but if i put (for example) 'color Red * 200'  i see the red line on the internal
> > bars.
>
> your light source, bars and projection object all end on x = 0,
> this coincidence is likely to get you into numerical issues. Also,
> at a grazing angle diffuse illumination is close to 0 but becomes
> visible if you boost the light power by 200.

Hi Christian i have another question , I insert in my scene a mirror and i noted
that if i leave a spotlight source the reflection (on a cylinder that i put in a
scene) doesn't work. Instead if i put a normal source light the reflection works
correctly. I think this is due on the settings on a spotlight to falloff and
tightness to 0. But i need this setting as you suggested me in the previus post.
There is a way to leave falloff and tightness to 0 so that also the reflection
work correctly? I posted a code. ( i commented spotlight now). Thanks a lot.

#include "colors.inc"
#include "textures.inc"
#include "shapes.inc"
#include "metals.inc"
#include "glass.inc"
#include "woods.inc"
#include "stones.inc"



declare rapportoAngoloApertura= 0.54;


global_settings {
    assumed_gamma 1
    max_trace_level 15
    photons {
        spacing 0.025
         count 18000000
        max_trace_level 15

    }
}


 // camera look of reflection of mirror
camera {
//orthographic
location <15.0, 50.0,120.0>
look_at <15.0, 10.0, 40.0>
blur_samples 50

       }

 // projector
 declare a= 1;
 declare b=rapportoAngoloApertura;
 declare Projector = prism   {
          linear_spline
           3, 3.002, 4,
          //funzia riflessione 3, 3.1, 4,
          <0,0>, <-a,b>,<a,b>, <0,0> //outer rim
           texture{ pigment{ color Green } }


        }

light_source{ <0,3.001,-0.2>

        color Red  *250

        // if i put spotlight the reflection of mirror doesn't work...
        /*spotlight
        radius 80
        falloff 0
        tightness 0
         point_at <0, 3.015, 2>
        photons {refraction off reflection on}   */

        projected_through { Projector }
        //shadowless
 } //end of light_source




 //mirror

 prism {
      cubic_spline
      1,
      5,
      56,
      <-48.500000, 16.500000>, //punto di controllo
      <-48.500000, 16.500000>,
      <-46.956445, 17.531168>,
      <-45.574971, 18.461886>,
      <-44.333273, 19.305708>,
      <-43.212883, 20.073862>,
      <-42.198386, 20.775732>,
      <-41.276812, 21.419218>,
      <-40.440374, 22.008760>,
      <-39.675929, 22.552711>,
      <-38.975541, 23.055922>,
      <-38.332364, 23.522584>,
      <-37.740461, 23.956339>,
      <-37.194656, 24.360364>,
      <-36.692357, 24.735995>,
      <-36.227347, 25.087338>,
      <-35.796160, 25.416532>,
      <-35.395729, 25.725477>,
      <-35.023326, 26.015864>,
      <-34.676523, 26.289204>,
      <-34.354393, 26.545856>,
      <-34.053565, 26.788154>,
      <-33.772312, 27.017183>,
      <-33.509077, 27.233921>,
      <-33.262452, 27.439254>,
      <-33.031164, 27.633989>,
      <-32.814897, 27.818141>,
      <-32.611649, 27.993177>,
      <-32.420477, 28.159700>,
      <-32.240518, 28.318264>,
      <-32.070983, 28.469375>,
      <-31.911149, 28.613501>,
      <-31.760940, 28.750536>,
      <-31.619089, 28.881467>,
      <-31.485045, 29.006654>,
      <-31.358299, 29.126432>,
      <-31.238379, 29.241112>,
      <-31.124852, 29.350982>,
      <-31.017735, 29.455897>,
      <-30.916190, 29.556557>,
      <-30.819875, 29.653190>,
      <-30.728477, 29.746009>,
      <-30.641700, 29.835213>,
      <-30.559273, 29.920990>,
      <-30.481245, 30.003190>,
      <-30.407043, 30.082329>,
      <-30.336448, 30.158556>,
      <-30.269257, 30.232014>,
      <-30.205279, 30.302836>,
      <-30.144337, 30.371148>,
      <-30.086491, 30.436809>,
      <-30.031336, 30.500210>,
      <-29.978726, 30.561454>,
      <-29.928528, 30.620638>,
      <-48.500000, 16.500000>,
      <-29.928528, 30.620638> // punto di controllo


    texture {Chrome_Metal}
    finish { reflection 1  metallic 1.0 diffuse 0 conserve_energy}
    translate z*27
    translate x*3
    photons {
  target
  reflection on


 }


}

Projector

// cylinder for test reflection
 cylinder {
<0, 0, 25>, // centro di un'estremità
<0, 30, 25>, // centro dell'altra estremità
5 // raggio
//open // elimina le facce piane
texture { T_Stone25 }
//pigment { Green }

translate x*-10
translate z*8



}


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From: Christian Froeschlin
Subject: Re: ray of light line laser with projector
Date: 16 Feb 2012 03:07:24
Message: <4f3c72ec$1@news.povray.org>
CRIS wrote:
> Christian Froeschlin <chrfr [at] chrfrde> wrote:
>> CRIS wrote:
>>
>>> Rather about my second question, maybe I explained bad, if i put in the
>>> spotlight source : 'color Red * 1' i don't see the light on the internal bars
>>> but if i put (for example) 'color Red * 200'  i see the red line on the internal
>>> bars.
>> your light source, bars and projection object all end on x = 0,
>> this coincidence is likely to get you into numerical issues. Also,
>> at a grazing angle diffuse illumination is close to 0 but becomes
>> visible if you boost the light power by 200.

> There is a way to leave falloff and tightness to 0 so that also the reflection
> work correctly? I posted a code. ( i commented spotlight now). Thanks a lot.

Actually I misinterpreted the falloff value, it should
be equal to radius for a sharp edge, not 0. So if you set
falloff 80 you again get the reflections.


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From: CRIS
Subject: Re: ray of light line laser with projector
Date: 17 Feb 2012 10:45:00
Message: <web.4f3e2f0b8af170f5ba9d93b20@news.povray.org>
Christian Froeschlin <chrfr [at] chrfrde> wrote:
> CRIS wrote:
> > Christian Froeschlin <chrfr [at] chrfrde> wrote:
> >> CRIS wrote:
> >>
> >>> Rather about my second question, maybe I explained bad, if i put in the
> >>> spotlight source : 'color Red * 1' i don't see the light on the internal bars
> >>> but if i put (for example) 'color Red * 200'  i see the red line on the internal
> >>> bars.
> >> your light source, bars and projection object all end on x = 0,
> >> this coincidence is likely to get you into numerical issues. Also,
> >> at a grazing angle diffuse illumination is close to 0 but becomes
> >> visible if you boost the light power by 200.
>
> > There is a way to leave falloff and tightness to 0 so that also the reflection
> > work correctly? I posted a code. ( i commented spotlight now). Thanks a lot.
>
> Actually I misinterpreted the falloff value, it should
> be equal to radius for a sharp edge, not 0. So if you set
> falloff 80 you again get the reflections.

Yes it works!!
thanks.


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