Here are images which document the difference between pointlight and
spotlight interactions with atmospheric media.  If that's the way it's
supposed to be, then so be it. This difference is quite annoying to me
as it goes against my intuition that point and spot lights should be the
same kind of animule, just different in their directional coverage.

(Apologies for earlier claiming it was a problem with the superpatch. I
have seen the same thing happen in 3.1g and sup 3.1e.)

The code allows either a point light or spot light to shine out of a
hole in a hollow sphere...

#include "colors.inc"
camera {
    location <0, 450, -900>
    look_at <0, 300, 0>
    angle 45
    }
light_source {  <0,0,0>
   color White*50

//Comment out this line or not to switch between point and spotlight..
   // spotlight    radius 45    falloff 28    point_at y
//yes, that line just above here, comment it out.

   media_interaction on
  }


light_source{<0,5550,0>  color White*2 media_interaction off}
difference{
        sphere{0,300 pigment {White}}
        sphere{0,299 pigment {Green}}
        cylinder{<0,0,0>,<0,500,0>,25 pigment {Green}}
        pigment {White}
        finish {ambient 0.2}
        }

sphere {<0,450,0>,10
        pigment {White}
        }
media {
   intervals 10
   scattering { 2, red 0.05 blue 0.001 green 0.02}
   samples 1, 10
   confidence 0.9999
   variance 1/1000
   ratio 0.9
 }

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Preview of image 'pointspot.jpg'

Is the 'falloff' number right? "28"?  Far as I know 'radius' should be
smaller or equal to 'falloff', and if it's larger then the falling off
wouldn't show.  Any chance this means you somehow unknowingly raised the
intensity of the spotlight through some quirk in the way it works?

Bob

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On Sun, 10 Oct 1999 15:43:41 -0400, Greg M. Johnson wrote:
>This is a multi-part message in MIME format.
>--------------0F39FD1270EE228044A619BF
>Content-Type: text/plain; charset=us-ascii
>Content-Transfer-Encoding: 7bit
>
>Here are images which document the difference between pointlight and
>spotlight interactions with atmospheric media.  If that's the way it's
>supposed to be, then so be it. This difference is quite annoying to me
>as it goes against my intuition that point and spot lights should be the
>same kind of animule, just different in their directional coverage.

Try adding this line at the end of your scene:

cone { 0, 0, 600*y, 50 pigment {rgbt 1} hollow}

See my posting from a couple weeks ago on why this has the effect it
does.  (povray.general, I think.  Something about media tutorials or 
such.  Maybe someone could post a more complete reference?)

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Ron Parker wrote:
> 
> See my posting from a couple weeks ago on why this has the effect it
> does.  (povray.general, I think.  Something about media tutorials or
> such.  Maybe someone could post a more complete reference?)

It started with my question:

publications about media method?

at povray.general

Fri, 17 Sep 1999

Ron gave the answer there!

Greetings,

Marc

-- 
Marc Schimmler

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THANKS.

The key is to leave the media "out of" the interior of the sphere.  I had
received advice before but I interpreted it as suggesting that I put the
media INSIDE the hollow object or plane.  This didn't look that good with the
scene I was considering at the time. With media inside the hollow object,
there was too much attention drawn to the interface of the object.  (BTW, a
sphere, rather than a cone, would be needed for my ultimate project: light
pouring out of a porous 3dnoise isosurface!)


sphere { 0, 400 pigment {rgbt 1} hollow

// comment out the 1st or 2nd line following
}
//interior{

media {
   intervals 10
   scattering { 2, red 0.05 blue 0.001 green 0.02}
   samples 1, 10
   confidence 0.9999
   variance 1/1000
   ratio 0.9
 }
       }
//uncomment out the next line if you uncomment out the 2nd line above.
//}



Ron Parker wrote:

> On Sun, 10 Oct 1999 15:43:41 -0400, Greg M. Johnson wrote:
> >This is a multi-part message in MIME format.
> >--------------0F39FD1270EE228044A619BF
> >Content-Type: text/plain; charset=us-ascii
> >Content-Transfer-Encoding: 7bit
> >
> >Here are images which document the difference between pointlight and
> >spotlight interactions with atmospheric media.  If that's the way it's
> >supposed to be, then so be it. This difference is quite annoying to me
> >as it goes against my intuition that point and spot lights should be the
> >same kind of animule, just different in their directional coverage.
>
> Try adding this line at the end of your scene:
>
> cone { 0, 0, 600*y, 50 pigment {rgbt 1} hollow}
>
> See my posting from a couple weeks ago on why this has the effect it
> does.  (povray.general, I think.  Something about media tutorials or
> such.  Maybe someone could post a more complete reference?)

Post a reply to this message

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