First of all, do I have the basic concept right?  The docs are incomplete.
My feeling is that using photons in the global_settings will cause all light
sources to shoot photons at objects that have reflection/refraction photons
turned on, and then =all= objects (unless marked ignore) are illuminated by
these photons.

What are "global photons", as in "Light sources can also generate global
photons. To enable this feature, put the keyword global in the light
source's photon block." ?

A glass object's shadow is totally black
(http://green.dlugosz.com/files/photon_try_1.jpg ).  Why is this, and how
can I get the shadow lighter?

--John

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In article <3aabe409$1@news.povray.org> , "John M. Dlugosz" 
<joh### [at] dlugoszcom> wrote:

> What are "global photons", as in "Light sources can also generate global
> photons. To enable this feature, put the keyword global in the light
> source's photon block." ?

Using "global_photons" is not recommended right now (because they don't
work perfectly, they are kind of experimental).  For now you should only
use photons for individual objects as explained in the MegaPOV
documentation and sample files.  Doing so will assume compatibility of
your scene with POV-Ray 3.5.


      Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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Are you saying simply don't use the "global" keyword in either place (light
source or global_settings), and the rest of the example in the manual is OK?
That is, there is still stuff in the "global_settings" block -- that has
nothing to do with global photons?

And just what are global photons?

--John

"Thorsten Froehlich" <tho### [at] trfde> wrote in message
news:3aac260b@news.povray.org...
> In article <3aabe409$1@news.povray.org> , "John M. Dlugosz"
> <joh### [at] dlugoszcom> wrote:
>
> > What are "global photons", as in "Light sources can also generate global
> > photons. To enable this feature, put the keyword global in the light
> > source's photon block." ?
>
> Using "global_photons" is not recommended right now (because they don't
> work perfectly, they are kind of experimental).  For now you should only
> use photons for individual objects as explained in the MegaPOV
> documentation and sample files.  Doing so will assume compatibility of
> your scene with POV-Ray 3.5.
>
>
>       Thorsten
>
>
> ____________________________________________________
> Thorsten Froehlich, Duisburg, Germany
> e-mail: tho### [at] trfde
>
> Visit POV-Ray on the web: http://mac.povray.org

Post a reply to this message

In article <3aad6f56$1@news.povray.org> , "John M. Dlugosz" 
<joh### [at] dlugoszcom> wrote:

> Are you saying simply don't use the "global" keyword in either place (light
> source or global_settings), and the rest of the example in the manual is OK?
> That is, there is still stuff in the "global_settings" block -- that has
> nothing to do with global photons?

Exactly.  Only the "global" keyword should not be used.

> And just what are global photons?

Photons that are "everywhere" compared to those that only work on
individual objects.


    Thorsten


____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

Post a reply to this message

In article <3aabe409$1@news.povray.org>, "John M. Dlugosz" 
<joh### [at] dlugoszcom> wrote:

> A glass object's shadow is totally black
> (http://green.dlugosz.com/files/photon_try_1.jpg ).  Why is this,

It happens because almost all light is being refracted away from those 
areas.


> and how can I get the shadow lighter?

Use radiosity to get indirect illumination from surrounding objects and 
that media glow in the middle, and/or use more light sources to 
illuminate the shadows.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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That brings up a deeper question of just how photons work.  That is, it
seems to take the place of regular shadow calculations?  Hmm, I suppose it
works by saying that any object that uses photons will turn completely
opaque to the regular lighting code, and any light that comes through will
be added by the photon illumination instead.

And you answered another question as well, and that being whether radiosity
can be used with photons or if photons takes the place of (is a superset of)
radiosity.

Any idea what causes the black streak in the middle of the wall?  I always
figured it was a shadow of the tip of the glass, but the streak is in all
directions, not just where the tip is.

Thanks for the insight, as always.

--John

"Chris Huff" <chr### [at] maccom> wrote in message
news:chrishuff-2D35C4.22070612032001@news.povray.org...
> In article <3aabe409$1@news.povray.org>, "John M. Dlugosz"
> <joh### [at] dlugoszcom> wrote:
>
> > A glass object's shadow is totally black
> > (http://green.dlugosz.com/files/photon_try_1.jpg ).  Why is this,
>
> It happens because almost all light is being refracted away from those
> areas.
>
>
> > and how can I get the shadow lighter?
>
> Use radiosity to get indirect illumination from surrounding objects and
> that media glow in the middle, and/or use more light sources to
> illuminate the shadows.
>
> --
> Christopher James Huff
> Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
> TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
>
> <><

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"John M. Dlugosz" wrote:

> Any idea what causes the black streak in the middle of the wall?  I always
> figured it was a shadow of the tip of the glass, but the streak is in all
> directions, not just where the tip is.

It's not a shadow. What kind of object was used to create the wall ?

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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In article <3aaec0db$1@news.povray.org>, "John M. Dlugosz" 
<joh### [at] dlugoszcom> wrote:

> Any idea what causes the black streak in the middle of the wall?  I 
> always figured it was a shadow of the tip of the glass, but the 
> streak is in all directions, not just where the tip is.

It looks like a solver error...is the wall or glass a sor, lathe, poly, 
or anything else which can use the sturmian root solver? If so, did you 
try using "sturm" or moving the camera/light source around a bit?

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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"Ken" <tyl### [at] pacbellnet> wrote in message
news:3AAEDE69.DF5EB5B0@pacbell.net...
>
> It's not a shadow. What kind of object was used to create the wall ?

It's supposed to be a curved wall.  Full source file is at
http://green.dlugosz.com/files/lamp1.3.pov .

That object is:

difference {
   intersection {
      cylinder { <0,0,0>, <0,18,0>, 12 }
      plane { -z, 0 }
   } // end of intersection
   cylinder { <0,0,0>, <0,18,0>, 11.5 }
   pigment { color red 0.858824 green 0.439216 blue 0.576471 }
   finish {
      ambient 0.15
      diffuse 0.6
      specular 0.6
   }
   scale <1.6,1,1>
} // end difference

Thanks for the insight,
--John

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"Chris Huff" <chr### [at] maccom> wrote in message news:chrishuff-> > Any
idea what causes the black streak in the middle of the wall?  I
> > always figured it was a shadow of the tip of the glass, but the
> > streak is in all directions, not just where the tip is.
>
> It looks like a solver error...is the wall or glass a sor, lathe, poly,
> or anything else which can use the sturmian root solver? If so, did you
> try using "sturm" or moving the camera/light source around a bit?

It's a simple curve made with a cylinder.  I tried moving the light source a
tad, nothing I can use with strum.  I posted the code in a reply to Ken.

--John

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