Tim,

Sorry for the confusion, I did not use the expression "specular reflection"
in a precise enough manner. What I really meant was that the photons would
be reflected specularly. Not that we would see specular reflection of other
objects in the objects.

The difference is that when a photon is bounced from a specular surface, it
is bounced back *only* in the mirror direction from the surface normal.
While when a photon is bounced from a diffuse surface, it is bounced back in
*all* directions. Because of that, global photons do not produce caustics.
They will just add more radiance to alreadu illuminated objects.

Regards,

White Zebra

"Tim Nikias" <tim### [at] gmxde> wrote in message
news:3e55765e$1@news.povray.org...
> What I suggested wouldn't give you specular
> reflections. Photons will be reflected off of specular-
> reflecting objects, which, when using no_image, won't
> show up on the final image. Thus, you need to place
> the same object, but in this case may change texture,
> normal, finish... So you can also leave out the reflection.
>
> You should look up on no_image, no_shadow,
> no_reflection for that.
>
> And in case this wouldn't work, you could still save the
> photons using specular-reflection, and then load them
> into the same scene, but with all specular reflections
> turned off.
>
> I'll post a short example when I've finished one.
>
> Regards,
> Tim
>
> --
> Tim Nikias
> Homepage: http://www.digitaltwilight.de/no_lights/index.html
> Email: Tim### [at] gmxde
>
> > Tim,
> >
> > Global photon mapping isn't implemented in POV-Ray. I've checked in the
> > source and there are some blocks of codes related to "GLOBAL_PHOTONS"
which
> > are not compiled. I guess that is because it is not flly functional or
fully
> > debugged.
> >
> > Yoursuggestion wouldn't work because it would produce specular
reflections.
> > I actually tried something similar to what you suggest. What I need is
> > diffuse reflection.
> >
> > Thanks for the suggestion. But I guess I'll wait for the global photons
to
> > be fully implemented and debugged.
> >
> > Black Zebra
> >
> > "Tim Nikias" <tim### [at] gmxde> wrote in message
> > news:3e5553c6@news.povray.org...
> > > As I've read the other comments on this, here goes:
> > >
> > > Photon-light-mapping is used to reflect or refract light
> > > off of either reflecting or refracting (transparent objects
> > > with any ior-value, even the default), so for refraction to
> > > work properly with photons, the object needs to be
> > > transparent or filtering to let some light travel through
> > > the object. In order to reflect photons, the object needs
> > > to have reflection in the finish{} Block.
> > >
> > > In order to achieve what you want, it might be possible
> > > to supply two objects, one with no_image and reflection,
> > > the other without reflection and without no_image.
> > > The no_image-object will be the target for photons, but
> > > won't show up on the image itself, thus you're non-reflecting
> > > objects SEEM to reflect photons.
> > >
> > > But this might not work. Then you'd have to do two passes:
> > > Render the scene with photons and all objects that reflect
> > > photons have reflection, save the photons. The second
> > > pass will be to load the photons, but keep the object without
> > > reflection.
> > >
> > > One of these, at least the last, should work.
> > >
> > > --
> > > Tim Nikias
> > > Homepage: http://www.digitaltwilight.de/no_lights/index.html
> > > Email: Tim### [at] gmxde
> > >
> > > > I'm trying to code the cornell box but using Photons Mapping instead
of
> > > > radiosity. So far, no success. I've got all my photons{} blocs in my
> > > > global, light and objects. The scene is very simple but all I get is
> > > > essentially the same render as with ray-trace only.
> > > >
> > > > Can anybody suggest something I might have missed?
> > > >
> > > > Thanks.
> > > >
> > > > Here is the scene file:
> > > >
> > > > global_settings {
> > > >   assumed_gamma 1.0
> > > >   max_trace_level 5
> > > >   photons {
> > > >     count 100000
> > > >     max_trace_level 9
> > > >   }
> > > > }
> > > >
> > > > #declare Finish=finish{diffuse 0.75 ambient 0}
> > > >
> > > > #declare White=texture{pigment{rgb<1,1,1>} finish{Finish}}
> > > > #declare Red=texture{pigment{rgb<0.57,0.025,0.025>} finish{Finish}}
> > > > #declare Green=texture{pigment{rgb<0.025,0.236,0.025>}
finish{Finish}}
> > > >
> > > > #declare LightColor=<1,0.67,0.21>;
> > > >
> > > >
> > > > light_source{
> > > >   <27.8,54.88,27.95>
> > > >   color LightColor
> > > >   spotlight radius -90 falloff 90 tightness 1 point_at
<27.8,0,27.95> //
> > for
> > > > cosine falloff
> > > >   photons {
> > > >     refraction on
> > > >     reflection yes
> > > >   }
> > > > }
> > > >
> > > >
> > > > camera{
> > > >   location  <27.8, 27.3,-80.0>
> > > >   direction <0, 0, 1>
> > > >   up        <0, 1, 0>
> > > >   right     <-1, 0, 0>
> > > >   angle 39.5
> > > > }
> > > >
> > > >
> > > > // ------------------------ OBJECTS ----------------------------
> > > >
> > > > // Light Patch
> > > > box{
> > > >   <21.3,54.87,33.2><34.3,54.88,22.7> no_shadow
> > > >   pigment{rgb<1,1,1>} finish{ambient 0.78 diffuse 1}
> > > >   photons {
> > > >     target
> > > >     refraction off
> > > >     reflection yes
> > > >     collect off
> > > >   }
> > > > }
> > > >
> > > > union{
> > > >   // Floor
> > > >   triangle{<55.28, 0.0, 0.0>,<0.0, 0.0, 0.0>,<0.0, 0.0, 55.92>}
> > > >   triangle{<55.28, 0.0, 0.0>,<0.0, 0.0, 55.92>,<54.96, 0.0, 55.92>}
> > > >   // Ceiling
> > > >   triangle{<55.60, 54.88, 0.0>,<55.60, 54.88, 55.92>,<0.0, 54.88,
> > 55.92>}
> > > >   triangle{<55.60, 54.88, 0.0>,<0.0, 54.88, 55.92>,<0.0, 54.88,
0.0>}
> > > >   // Back wall
> > > >   triangle{<0.0, 54.88, 55.92>,<55.60, 54.88, 55.92>,<54.96, 0.0,
> > 55.92>}
> > > >   triangle{<0.0, 54.88, 55.92>,<54.96, 0.0, 55.92>,<0.0, 0.0,
55.92>}
> > > >   texture {White}
> > > >   split_union off
> > > >   photons {
> > > >     target 1.0
> > > >     refraction off
> > > >     reflection yes
> > > >     collect off
> > > >   }
> > > > }
> > > >
> > > > union {
> > > >   // Right wall
> > > >   triangle{<0.0, 54.88, 0.0>,<0.0, 54.88, 55.92>,<0.0, 0.0, 55.92>}
> > > >   triangle{<0.0, 54.88, 0.0>,<0.0, 0.0, 55.92>,<0.0, 0.0, 0.0>}
> > > >   texture {Green}
> > > >   split_union off
> > > >   photons {
> > > >     target 1.0
> > > >     refraction off
> > > >     reflection yes
> > > >     collect off
> > > >   }
> > > > }
> > > >
> > > > union {
> > > >   // Left wall
> > > >   triangle{<55.28, 0.0, 0.0>,<54.96, 0.0, 55.92>,<55.60, 54.88,
55.92>}
> > > >   triangle{<55.28, 0.0, 0.0>,<55.60, 54.88, 55.92>,<55.60, 54.88,
0.0>}
> > > >   texture {Red}
> > > >   split_union off
> > > >   photons {
> > > >     target 1.0
> > > >     refraction off
> > > >     reflection yes
> > > >     collect off
> > > >   }
> > > > }
> > > >
> > > > box {
> > > >   // Short bloc
> > > >   <-8.35,0,-8.35>,<8.35,16.5,8.35>
> > > >   rotate <0,-17,0>
> > > >   translate <18.6,0,16.85>
> > > >   texture { White }
> > > >   photons {
> > > >     target 1.0
> > > >     refraction off
> > > >     reflection yes
> > > >     collect off
> > > >   }
> > > > }
> > > >
> > > >
> > > > box {
> > > >   // Tall bloc
> > > >   <-8.35,0,-8.35>,<8.35,33,8.35>
> > > >   rotate <0,17,0>
> > > >   translate <36.85,0,35.15>
> > > >   texture { White }
> > > >   photons {
> > > >     target 1.0
> > > >     refraction off
> > > >     reflection yes
> > > >     collect off
> > > >   }
> > > > }
> > > >
> > > > WhiteZebra
> > > >
> > >
> > >
> >
> >
>
>

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