[Radiance-general] perfect specular reflection in rtrace

[Jan Wienold]

Hi Antoine,
specular reflections are not traced at all to light sources in the ambient calculation (which you invoke by -I). Only to glow material. Thats why also the reflections of the sun on glass-material is not captured by rtrace -I.
So either you use mirror material and a -dr >2 or you calculate a 180degree fisheye on you point and calculate the illuminace from the image. The view rays for the image are traced via specular surfaces towards light sources.
Jan

On 12 October 2017 19:22:28 CEST, Antoine Bugeat <bugeatantoine at gmail.com> wrote:
>Hello all,
>
>I'm a civil engineering student and I'm trying to compute the impact of
>specular reflections in a street "canyon".
>My problem is:
>I use rtrace function with the basic parameters, the same as DAYSIM
>uses
>(-I -aa 0.1 -ab 5 -ad 1000 -ar 300 -as 20 -dj 0 -dr 5 -ds 0.2 -dp 512
>-lr 6
>-lw 0.004 -st 0.1 -oov)
>My sky and sun description come from gendaylit.
>My wall is defined by a perfect specular plastic and the ground is
>defined
>by a diffuse material.
>
>When I do the simulation, I get illogical results as if the specular
>reflection of the walls had no impact.
>
>So, I tried to simulate a really simple scene with only one *specular
>surface*:
>
>void plastic M_Spec
>0
>0
>5 0 0 0 1 0
>
>M_Spec polygon 1
>0
>0
>12 -5.0 0.0 -5.0
>-5.0 0.0 5.0
>5.0 0.0 5.0
>5.0 0.0 -5.0
>
>My *source* is described as a sun perfectly perpendicular to the
>surface:
>
>void light solar
>0
>0
>3 1000 1000 1000
>
>solar source sun
>0
>0
>4 0.0 -1.0 0.0 0.5
>
>And the *sensor* is between the surface and the source and is regarding
>right to the surface:
>
>0.0 -5.0 0.0 0.0 1.0 0.0
>
>And in this case, I get 0 after my rtrace simulation.
>I tried to vary some parameters of rtrace (direct and specular
>parameters)
>but it change nothing I still get 0.
>
>Thank you for your help.
>
>Antoine Bugeat

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