Christian Froeschlin <chr### [at] chrfrde> wrote:
> Crippso wrote:
>
> > thanks Clipka, ok so I try the code below to try and see the fresnel reflected
> > light from the mirror onto a diffuse disc but it still doesnt work. Am i doing
> > something wrong?
>
> shooting photons perpependicular to the mirror surface as
> in your setup is precisely where fresnel reflection is 0.
> I moved the mirror and light and get a rectangle on the
> disc that is the reflected image of the box.
>
> Also note that the diffuse surface does not require
> a photon block as it should not be a target, and collect
> is on by default. Also you'll get a more interesting
> reflection if you remove parallel and point_at.
>
>
> #local p_start  = 0.1;
> #local p_end_final = 0.05;
>
> #local final_eb  = 0.5;
> #local final_count = 50000;
>
>
> #default {finish {ambient 0 diffuse 0}}
>
> global_settings
> {
>    assumed_gamma 1
>    max_trace_level 50 photons{count 575000}
> }
>
>
> camera
> {
>    orthographic
>    location <0,0,1>
>    look_at  <0,0,-1>
>    angle 90
> }
>
> light_source{<10,0,-1>, 1 parallel point_at <5,0,2>}
>
> box
> {
>    <-0.5,-0.5,2> <0.5,0.5,3>
>    pigment{rgbt 1}
>    finish
>    {
>      reflection{0,1 fresnel}
>      conserve_energy
>    }
>    interior{ior 1.5}
>    photons
>    {
>      target
>      reflection on
>      refraction on
>      collect off
>    }
>    translate 5*x
> }
>
>
> disc
> {
>    <0,0,-1> <0,0,1> 1
>    pigment{rgb 1}
>    finish{diffuse 1.0}
> }

Thanks for the reply - but i notice you say that when the photons are
perpendicular to the surface the fresnel reflection will be precisely 0. Is this
really true in povray? In the real world the fresnel reflection would be 2 times
((1.5-1)/(1.5+1))^2 = 0.08.

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