[Radiance-general] perfect specular reflection in rtrace

[Nathaniel Jones]

Hi Antoine,

Your plastic is completely black, so it won't reflect any light. You need
to set the red, green, and blue values to be positive numbers. For
instance, if you want a 50% reflective wall:

void plastic M_Spec
0
0
5 0.5 0.5 0.5 1 0

But is there a reason you're using plastic? Plastic that is 100% specular
isn't realistic, and more to the point for your use, it won't give you very
good reflections of small sources like the sun; for this, you will need to
use a mirror material.

Nathaniel

On Thu, Oct 12, 2017 at 10:22 AM, 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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