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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